There's an entire genre of these kinds of books that extrapolate generalities (life throughout the Universe) from a single data point (life on Earth), but the truth is, that's not even an educated guess.
We do not know if our evolutionary pressures are universal. We do not know if the evolutionary solutions developed here are appropriate even on other Earth-like planets, much less everywhere. Sensitive dependence on initial conditions could lead to radically different planetary environments, necessitating radically different mechanical solutions to survival, some (many, most?) of which we will never have even imagined.
What creatures would form under an intense magnetic field? In methane? In close orbit around a dim star? In a hot cloud nebula? Could we even recognize them as alive, much less intelligent? Definitely not if we're looking for bats and monkeys and octopuses
No, I think the whole genre of "life is much the same everywhere" suffers from a profound lack of imagination
Physics and chemistry impose some serious constraints on all life forms. On earth we have convergent evolution, independent groups of species independently develop similar solutions for a specific problem. Life on other planets will have similar problems, e.g. reproduction, locomotion and perception of its environment, and its solutions will probably be similar to the ones we have on earth.
First we need to decide how intelligent are the dolphins, then let us look at the stars.
Every single life form on Earth today had exactly the same time to do its evolution in. Us, bats, dolphins, tapeworms, birch trees, amoeba, mushrooms, all of that had exactly the same chance(s) in the same time span.
And we don't even know if and how mushrooms and trees communicate, let alone if they "think", for our near-sighted definition of thoughts. We don't even know what to make of birds, e.g. crows, with respect to the size of their brains and what they can do.
Is our planet, taken as a whole, alive, in some form of the Gaia hypothesis? The correct answers as of this time are either "we don't know" or "it depends on the definition of alive."
That Star Trek trope of "everything in the Universe is just like us with different faces" really needs to be put to rest.
Even H.R. Giger was boring and unimaginative with regards to how he envisioned the Alien. That's clearly a creature influenced by Earth-ism - a quadruped, with a single head and mouth and a flexible spine and claws, it's basically a weird cat.
> That Star Trek trope of "everything in the Universe is just like us with different faces" really needs to be put to rest.
Budget constraints aside, Star Trek aliens were used as a prop to explore extremes of terrestrial human behaviour and culture from an outside perspective - take a human and remove emotions and have them governed purely by logic, you get a Vulcan. Take a human and exaggerate their tendencies towards violence and honour, you have a Klingon, and so on.
Even in the original series there were truly alien aliens - for example the Squire of Gothos was a being of pure energy who just assumed human form, Devil in the Dark had a silicon-based creature, and the Tholians were an intelligent crystalline species who could only exist in high temperatures.
In Star Trek TNG there was a story arc that culminated in the reveal of a precursor humanoid race that had seeded their genome around the galaxy so that they ultimately resulted in the “big” races like humans, Klingons, Vulcans, Cardassians and so on.
Even if you discount the semi-canonical explanation that the Alien was a mixture of human & "entirely fabricated" DNA, Giger's Alien was shaped the way it was for literally- and metaphorically-painful sexual artistic reasons, not as a serious hypothesis for alien life.
> First we need to decide how intelligent are the dolphins, then let us look at the stars.
The premise is wrong. The premise here is that intelligence is the only factor. Physics doesn't allow dolphins to enter the bronze age. Hell, even if dolphins grew arms and hands they couldn't enter the bronze age. They're probably smart enough to do so, but there are other factors limiting them.
We have looked at Earth. We can look to the stars at the same time. It isn't an "or" operation.
Yeah but we're not really talking about bronze ages or if a species can achieve comparable technology, but whether we can correctly detect intelligence, or even life, around us.
I don't think we should label dolphins as un-intelligent just because their physical environment doesn't allow them to smelt metal.
My point is - I'd like to avoid judging something as (not) alive or intelligent just because it is (or isn't) similar to our daily life.
> My point is - I'd like to avoid judging something as (not) alive or intelligent just because it is (or isn't) similar to our daily life.
I think this is fair, but I also think when people say "detect intelligent alien life" it is shorthand for "intelligent and technologically capable life that would also be able to develop things like radio and interstellar travel." The latter is pretty cumbersome. I don't think dolphins are unintelligent, I don't think an ant is either. But in this context that's not what we're talking about. Language has limits and we use shortcuts like this all the time. Let's just be clear what page we're on and let's try not to inject another page just because the same word is used to mean multiple things.
> Even H.R. Giger was boring and unimaginative with regards to how he envisioned the Alien. That's clearly a creature influenced by Earth-ism - a quadruped, with a single head and mouth and a flexible spine and claws, it's basically a weird cat.
When the franchise came into being, you're probably right. But in all fairness, the back story and the biological concepts in the Alien universe has been refined since then. For example, the human-like qualities of the xenomorph creature is now explained by the biological merger of an alien substance with the host. When a human was infected, the substance developed into a parasite that took-on characteristics of the host.
Fundamentally, the black goo (i.e. the substance) we saw in Prometheus was pretty much the source of all the alien creatures. It was basically an instrument that deconstructed existing life forms and rebuilt weaponised variants of them.
> Every single life form on Earth today had exactly the same time to do its evolution in. Us, bats, dolphins, tapeworms, birch trees, amoeba, mushrooms, all of that had exactly the same chance(s) in the same time span.
This is patently false as these species have very different places within the phylogenetic tree. Emphasis on tree, since their adaptivity experiments did not have a linear timeline either; we didn’t evolve to have speech from scratch, we’ve adopted existing partial solutions, e.g. having a tongue, to develop it.
And we don’t need to delve into phenomenology of being a mushroom, adaptivity gives us an observable proxy to the “intelligence” of an organism; how general and efficient of a problem solver they are, the ultimate problem being surviving genes onward. Turns out humans do exceptionally well, for the problems they’ve encountered so far. We’ll see if/how we can solve anthropogenic coordination problems of our day.
> That Star Trek trope of "everything in the Universe is just like us with different faces" really needs to be put to rest.
You need to cook a "complex adaptive organism" solution with the same periodic table and a handful of forces. It's like coding a CRUD application with slightly different sub-requirements and the exact same programming language. How different can they be?
If you need more creativity you have to break apart from physical requirements and the right genre for that is fantasy.
"And we don’t need to delve into phenomenology of being a mushroom, adaptivity gives us an observable proxy to the “intelligence” of an organism; how general and efficient of a problem solver they are, the ultimate problem being surviving genes onward."
By that logic the most intelligent animals is a cockroach
Viruses and prions reproduce, not only are they not intelligent, they are not even alive.
> By that logic the most intelligent animals is a cockroach
Firstly, please notice the quotes around intelligence; clearly we’re playing with a fast and loose definition.
Secondly, if humans had driven themselves into extinction with nuclear warfare, that would as well have been true.
Intelligence is not mere symbolic processing, nor symbolic processing is guaranteed to be adaptive, as evidenced with its failure modes in our perennial irrationalities.
> Viruses and prions reproduce, not only are they not intelligent, they are not even alive.
I know one particular virus twisting humanity’s arm these days, and in a way that is not fully intelligible to us yet. I wouldn’t readily diminish the internal logic that’s going on there.
Indeed. If there were civilizations that communicate on geological time scales, how would we even know they are alive? If whales and dogs and bats are too alien to communicate with, what hope do we have with aliens?
Completely agree - the vast differences in the Earth's species and their intelligence should be an indication of the enormous range of possibilities we should expect...Saying that, since "most intelligent" species on Earth are bipedal, it means it's most likely intelligent aliens would be too, does not only seem ignorant to the sheer number of factors and possibilities, but also to other species on Earth and ways intelligence can be manifested.
But changes in the environment and initial starting point can result in very different approaches. For example land mammals, reptiles and fish are quite different from each other. Because they've "always been here" we don't appreciate how different they are. Imagine if we had no fish and then found a planet with water that had fish in it -- that would seem absolutely shocking to see animals that could breathe underwater.
Honestly this would be pretty hard to imagine. Even if we had no concept of fish (which I find extremely unlikely given other evolutionary pressures, physics, and mechanics of life, but let's not go there) we would think "birds, but in a denser fluid." I don't think this would be "absolutely shocking" to biologists of that planet. Similarly like how biologists here have predicted methane based lifeforms. Now if we were talking about a fluid like sulfuric acid then yeah, that would be absolutely shocking, but not for the reasons of breathing (it's about electrons).
And all these animal/alien minds swim through time like a fish swims through water. Reminds me of that David Foster Wallace joke.
> There are these two young fish swimming along, and they happen to meet an older fish swimming the other way, who nods at them and says, “Morning, boys. How’s the water?” And the two young fish swim on for a bit, and then eventually one of them looks over at the other and goes, “What the hell is water?”
Both mammals and reptiles that live in the water use very similar methods even though they are not at all closely related. It is an example of convergent evolution.
> Physics and chemistry impose some serious constraints on all life forms.
On earth's carbon based life forms you mean. Its a huge blindspot, basically monkeys looking for other monkeys. If we believe our life is sufficiently compelex biochemically, it figures that other "life" may have the same complexity but with very different structures.
So the argument for ET life to have almost exact homologs of terrestial life is bordering on naievete at best, and dangerously intolerant at worst.
No, its more like saying “our star and the planets and most satellites in the solar system are generally spherical due to gravity. I postulate that all stars and planets in the universe are subject to those same forces and will also generally be spherical”. That isn’t a dangerously intolerant idea. We can say that life is unlikely to arise from a solid block of iron, due to what we understand about the atomic properties of iron, the possible chemical reactions, etc. There just isn’t much going on at a basic physics level for it to “do” anything that could likely lead to even the most generous definition of “life”. That isn’t naivete.
It is your kind of fantastical thinking that life somewhere else somehow isn’t subject to the same physics as life here that is naive. It’s not wanting to be bound by boring concepts like chemical reactions, gravity, perceiving your environment in some way, etc. We don’t take people seriously that say that stars in other galaxies are actually the heads of long bright snakes and us thinking they are just boring balls of gas is our “blindspot”.
We don't know factually if a beetle can think and remember.
We know about proteins.
We don't know how some aquatic life can survive in the mariana trench.
Biochemistry is indeed chemistry but it isn't as straight forward as we'd like to imagine. Till this day there are cell structures we are uncertain of and would be completely wandering in the dark were it not for cheap but powerful computation available 24/7.
Lets go smaller and things get blurry. The standard model looks...hmmm.
> We don't know factually if a beetle can think and remember.
What does this mean? We don’t know the exact capacity of the mind of a beetle. We don’t know how its subjective experience compares to our own. But we know that the structure of neuronal tissue allows information to be stored, just like we know that the structure of DNA allows information to be stored. The relay on chemicals, temps, and pressures where weak chemical bonds and be reliably broken and made.
> We don't know how some aquatic life can survive in the mariana trench.
Again, what does this mean? This feels like the misunderstanding when we say “we don’t know how the pyramids were built” which means we don’t know everything about the exact methods used, but we understand the general technological levels of the time. While people take it as “the ancient Egyptians had a secret technology” or “they couldn’t have built them”. We haven’t been able to observe certain behaviors or exact mechanics or feeding habits for some animals, but we understand how they survive.
> Biochemistry is indeed chemistry but it isn't as straight forward as we'd like to imagine. Till this day there are cell structures we are uncertain of and would be completely wandering in the dark were it not for cheap but powerful computation available 24/7.
Understanding the exact mechanisms is not the same as understanding why cells would be round, or why a semi permeable membrane is important, or why they need energy to resist entropy, or how they need a reliable way to encode and store information,etc.
Understanding very specific and exact biological processes is not the same as understanding basic constraints placed on all matter. If its too cold for chemical reactions to regularly take place, that is a constraint. If a material does not have a structure that can be broken down and remade, that is a constraint. The inverse square law is true everywhere, which is why we can say we won’t see giant flying dragons on any planet.
The example of convergence between fish and dolphins, birds and insects, the infamous "why does everything evolve into crabs" study and so on should tell us that while we should be open for radically different forms of life, the most likely outcomes will look like something we've seen here on Earth.
I'm personally expecting something like 80% humanoids and 20% exotic forms. Maybe I'm primed incorrectly by cheesy soap operas and sci-fi TV shows, but I think they're not far off (even if for unrelated reasons like SFX/VFX budget and character empathy).
What are we referring to as humanoids though? And what are we about as intelligent? Crows? Crows aren't going to build spaceships and don't really have the means to because a beak isn't a great manipulator, even though they use tools. I don't think the person above is saying that quadrupeds would be out of the realm of possibility (maybe they are. IDK I'm a computer scientist, not a biologist. I could totally see body size, caloric intake ratios, and brain mass being related in a way that would make these unlikely), but rather things like fractaling appendages would be expected because intelligent life would need to have fine motor control. (Is a centaur humanoid?) There are just more efficient ways to do things than other ways. Yeah, maybe alien life will have a beak. Maybe their pupils will look different but I'd still expect them to have eyes with squishy lenses because that's pretty much required to be able to focus and intelligent creatures need to be able to sense things both near and far (without technological enhancements). Light sensing isn't enough if you want to build things, you need depth perception. I think if you follow this line of reasoning you'll find that a lot of attributes humans have would be pretty likely for intelligent alien life as well.
Yes but it is very expensive. Here's some more on bats[0] (mentions expensive echolocation around 5:45 and moving from sonic location to echolocation evolution). Eyes do also convey more information. You can get colors in addition to depth and shape and that's a good reason and easy path for eyes to develop since light sensing is a pretty easy thing to develop. Also, bats aren't blind, despite common belief.
Also consider an octopi's environment. That environment is not well suited for being able to build lots of things. How do you get to the bronze age underwater? How about even earlier. Land based creatures have pretty similar forms. Snake like, bipedal, quadru/multiped, and flying/winged creatures. Snakes don't have arms and so aren't going to have fine motor control. Winged creatures are going to have a hard time dealing with heavy objects (they have hollow bones to fly and wings are incredibly fragile and I don't see nature creating super materials, plastics, or metal structural systems for animals). Quadrupeds probably aren't going to develop arms like centaurs (more likely legs become arms). So if we want a creature that can have fine motor control, live in an environment that can easily create metals, not be extremely fragile, and is able to devote a significant amount of its energy intake to its brain, you're probably going to come up with something ape like (bipedal). There are other forms here, but we can see that there are some pretty good hints that we learn just from mechanics and aren't so much dependent on specifics of Earth or humans.
"Also consider a human's environment. That environment is not well suited for being able to build lots of things. How do you get to the <untranslatable> age on earth?"
Earlier, you mentioned that beaks can't make spaceships. Well, maybe neither can hands. What we call a spaceship might be laughable nonviable. In fact, we know it is.
We're struggling at limits that some other lifeform might not have. We're hill climbing for tools that will let us do things we really want to do. Quite likely a lot of our progress is orthogonal or even oppositional to what we need to do to get off the planet.
We have no idea if some of our progress might be backsliding or entirely halting our future progress. Due to our natures. Due to our beaks.
> Earlier, you mentioned that beaks can't make spaceships. Well, maybe neither can hands.
Except hands did create spaceships...
The "beaks can't make spaceships" is a comment about crows not having hands. Crows use their beaks to manipulate objects. This does not imbue cows with great motor control. The use of tools is very different than the ability to finely manipulate tools. Aliens could have beaks, but these would not be their way to build spaceships. Similarly they wouldn't have pincers. Such grasping mechanisms just are extremely inefficient and don't allow for certain tasks.This excludes a lot of classes of tools from crows. This isn't biology, this is physics.
Our hands are like beaks to some hypothetical species, and it is hubris to assume we're great manipulators. Our fingers could be closer in utility to cow's hooves, than the manipulation techniques of some unknown species are to our own gesticulations.
And they would have tools as multipliers for their natures, just as we use tools to extend ours.
Our wonderful inventions might be another species child's play. Our herculean efforts to reach the stars might be a triviality to a species that can synthesize novel compounds in their bodies, and/or those of their stock animals. We're just at the early stages of doing that with algae, after a very long climb from first making fire.
Just as I could train and arrange to walk to Mexico, they might be able to self modify and reach the stars. No spaceship needed.
Our great ideas and dreams might be trite to bigger minds out in the galaxies. They could have easily skipped over what we struggle with.
You call those cans "spaceships"? They can barely get to your moon and back.
"Humans can't even excrete flexible ceramics. They need air. They need heat. They can't stand up to ionizing radiation. This isn't biology, this is physics!"
Cephalopods have got onto land at least twice. Nothing says they can't do it again.
But this form is also extremely rare. You're also ignoring the main component of the argument, which is where calories are going, not that arms can come out of a body.
The calorie part is about where you're spending calories. Brain or body? This gets complex real fast though. One easy part to understand is surface area and volume (but there's also things like metabolic rate and many others that go in here). But consider that brains are pretty resource intensive. In a human it's 2% of the mass but 20% of the energy. There's a linear relationship between neurons and calories but humans are an outlier in percent of energy that goes to brains. Additionally, it is the third most resource intensive system (for humans), behind skeletal muscle and the liver[0]. Which those last two parts matter a lot. Skeletal muscle scales with volume. So if you're bigger you have to eat more. The more you have to eat the more time you have to spend eating and your metabolism is probably going to slow. So it gets really complicated here really fast (and I'm admitting to my naivety to the subject matter) but basically it's not hard to see here that if you're pretty big you're probably not going to have the resources (or metabolism) to spend time thinking, which means a downward selection pressure on brain and thinking. There's going to be a Goldilocks zone here (like most things).
So basically if you can get food and don't have to spend significant time thinking to do so, there isn't going to be a selective pressure to encourage brain growth. And if you have a selective pressure to devote energy to the brain you're also probably going to have a selective pressure to reduce energy from elsewhere.
Additionally, I'll add that humans both lost fur and stood up because it is better for thermal regulation (there are other pressures too, there's never _one_ reason). So this also helps with the surface area-volume issue.
Basically what I'm saying is that there's these locally optimal conditions that need to exist at the same time to produce intelligent, tool using, civilization making creatures. (I mentioned in another comment that environment matters too. Can't get a bronze age underwater. But I also didn't mention you can't get a bronze age if you don't have a social structure, something, for example, octopi lack). Basically what astrobiologists are looking for are the combination of these optima necessary to produce certain traits. What many commenters here are missing is the combination part, mostly thinking that only intelligence matters to create a space fairing civilization, but you can't get to space if you can't create advanced composites, explosives, and many other things. Or in other words, the astrobiologists aren't idiots and probably know what they are talking about despite what it looks like. It only looks like they are dumb because people are overly simplifying the problem.
Not disagreeing with you, but aren’t these local minimums/maximums quite dependent on eukaryotic cells, and/or protein-based life? Wouldn’t the resources required by the brain vs muscle be vastly different than what we have know?
Also, what if a non-protein based molecular machinery can be so energy efficient and powerful that species having that can skip some seemingly necessary part of development? But I’m by no means an expert on the topic, just asking. If the reasoning was about absolute limits, I would be much more accepting of them (eg. Energy required by the simplistic work done, like a given skeletal structure picking up a weight with muscles only consuming the minimal physical necessity)
Most of what I've mentioned is more physics based rather than biologically based. Even if your muscles are more efficient your skeleton is going to grow with volume, which means non-linearly. Given this, all those same things will still apply.
Brains are resource-intensive only if you are in a massive hurry. Starfish do fine, entirely without a structure you would call a brain. Packing it all into one noggin is risky, for no benefit. If you're not in a hurry, you don't need nearly as much of it, because it doesn't have to do everything at the same time.
There is no natural speed that life has to operate at. Any aliens we encounter are much more likely to be very, very slow, because it is they who can stand the vast chill void between stars. If they visit, and you dare to chop one down, you wouldn't find anything recognizable as brain inside.
Something resembling this has actually been observed in a species of deep sea snails. Iron sulfide is incorporated into the hard bits (shell, foot armor). (https://en.wikipedia.org/wiki/Scaly-foot_gastropod)
That's a wrong way to think about it, since all modern "humanoids" are descended from the same ancestor not that long ago.
And if you consider dinosaurs humanoid, then so is that meme cat that can walk on its two back legs.
If there was an apex predator in every tree of life, in the "humanoid" shape, and I'm talking "humanoid ants" here, then it would be reasonable to assume that there's something beneficial in the "humanoid" shape that helps long-term survival.
And that's not even taking the majority of lifeforms into account - those in the seas, and greatly discounts birds. We still can't agree on if dolphins and crows are intelligent.
So, no, chances that the "humanoid" shape is somehow special out there are basically 0, since it's not even special here on Earth. We're an accident. Insects, mushrooms, plants - all those life forms are better adapted for mere survival than us (judging by cumulative mass of live organisms).
That's the wrong way to think about it. Nothing is 'better adapted' than anything else. Each is adapted to its own niche. And no accidents really - convergent evolution shows that similar ecological pressures very very often result in similar forms. Witness fish ("there's no such thing as a fish") or trees ("there's no such thing as a tree").
And that dinosaur comment - I don't know what to do with that. Dinosaurs only walked on two legs in internet memes? That's so far wrong I can't comment.
Many convergent evolution paths led to the same similar form, in time. That was the point. If the environmental pressures are similar, the forms may be similar.
The convergence between dolphins and ichthyosaurs is even more remarkable. Ichthyosaurs were marine reptiles; air breathing tetrapods that, like dolphins, had ancestors that walked on land but eventually returned to the sea to kick fish ass.
Sure, organisms that already share a massive amount of commonalities can diverge and then converge again.
What about the branches that happened early on? We essentially have only two lineages of macroscopic organisms that are actually fundamentally different: Plants and animals.
I would expect any kind of macroscopic extraterrestrial life to be at least as distinct from Terran plant and animal life as they are from each other.
I think it's fine to lump fungi together with plants for the spirit of this discussion. The distinction between plants and fungi are made on the basis of metabolism but in this thread people are clearly talking about external behaviours observable with the naked eye.
Metabolism influences external attributes (I think behavior isn't the right word you're looking for). A larger creature requires higher caloric intake than a smaller creature (and this process isn't linear). A larger creature has different thermal regulations than smaller creatures because surface doesn't scale with volume linearly. The bigger the creature the more it calories it has to expend on the body vs the mind. There are equilibriums here that are physics based.
And then consider the selective pressures from plants vs fungi. A fungi gets its environment. Plants do some, but also need to perform photosynthesis. These have very different selective pressures for these lifeforms.
DNA is extremely flexible, there's no macroscopic form or shape it can't take, as various insects camouflaging themselves as sticks and leaves and what not shows.
So the idea we'll see some vastly different concepts with different starting blocks is possibly unfounded.
Alien life might be very different at low level depending on their environment, but in terms of macroshapes, things like the formation of a head with eyes and mouth, upper and lower limbs, bilateral symmetry and so on will repeat over and over.
Yeah, but so what? The geometric shape isn't very interesting. The insect camouflaging itself as a leaf still functions as an insect. It doesn't perform photosynthesis.
Considering that we have a whole class of lifeforms that have nothing like a head with eyes and mouth or limbs, the idea that this would evolve independently more likely than something completely different, is also possibly unfounded.
Having two eyes, as a simple example, is arguably the cheapest way to perceive 3d at things-may-want-to-eat-me distance: just two points that enable triangulation. Similar constraints reduce the configuration space a lot. It still remains huge, but I don’t think someone that believes about certain convergence to be necessarily naive.
> DNA is extremely flexible, there's no macroscopic form or shape it can't take, as various insects camouflaging themselves as sticks and leaves and what not shows.
That feels like a really bold claim given the evidence.
Physically you could have wheeled animals, but wheels just won't evolve. They are perfect for somewhat smooth surfaces where you want to travel in a somewhat straight line. Organisms just cannot confine themselves to that and survive.
Unless we find a planet composed entirely of solid smooth rock we won't find wheeled animals.
I completely disagree. I think the 'life can look like anything' (lets call them LCLLAs) train of thought suffers from a lack of understanding of constraint satisfaction.
Think about how some LCLLAS talked about how silicon life is probably a thing. First off, it it were, given Earth's crust is mostly silicon and its the most habitual place ever discovered, it would have evolved here. but it didnt. It turns out silicon is just too ridged, and to get life going you need all sorts of chemical properties that just aren't congruent to life.
We are carbon / oxygen organisms for a chemical reason. despite the availability of other resources, other forms of lifeforms didn't develop for a reason. maybe other forms of life does exist in some methane ocean on Saturn like planets, but its not going to be very complex, and definitely not intelligent life building space ships.
I'm just always surprised how can we be so certain? Even here on Earth, for millions of years, life was literally nothing more than single cell organisms - also definitely "not intelligent life building space ships". And it would be very hard to see how could it possibly evolve into such, seeing as the atmosphere was full of incredibly toxic oxygen.
The thing is, life has almost infinite time to evolve out of these various elements. The fact that it didn't evolve here on Earth means absolutely nothing, seeing as Earth alone has billions of years left where such life could arise, and there are literally countless planets everywhere in the universe where the random dice of evolution roll every second.
It’s a question of physics not just chemistry. Deuterium for example is similar to hydrogen chemically so while those differences are slightly toxic to us it’s easy to assume a planet similar to earth with an abundance of deuterium and a lack of hydrogen would evolve life forms with the opposite preferences.
Except the ratio of hydrogen to deuterium is a function of astronomy and more specifically fusion. No naturally formed planet is going to end up with that imbalance. Which means no natural deuterium based life forms. So while some alien civilization create deuterium life, it’s not going to be part of natural ecosystems.
And so it goes for most possible interesting edge cases. Dependency on rare elements like Neptunium means any competitors without that dependency have huge advantages.
Of course. But there are planets with abundance of silicon(including ours). There are planets with abundance of methane and even here we have lifeforms which can consume it. I'm just pointing out that as long as silicon based life is possible, then given the near infinite amount of time the universe can spend evolving such life, it will surely exist.
Sort of, it depends on how common various forms of proto life are. If their very rare and the first one to happen wins then you might expect silicon life of some form to be out there.
On the other hand if proto life is extremely common then silicon proto life might always be out competed by more efficient alternatives. For example the fact Silicon dioxide is a solid where carbon dioxide is a gas is a major advantage or using carbon.
The silicides would meanwhile say that the gaseous nature of CO2 makes carbon useless as a basis for life, and even go so far as to offer a plausible reason.
Sorry, no. CO2 being gaseous is a major availability and energy advantage. For example you can’t get plankton equivalents as dissolved silicon is parts per trillion at the oceans surface.
Hybrids are a different story, but I doubt that’s what anyone is talking about by silicon based life forms.
CO2 (or SiO2) is only one of the possible outputs, or inputs, of metabolism. Even on Earth its primacy came very, very late.
You don't get to constrain alien life to your preconceptions. Even some Earth life secretes SiO2. Using carbon for some things would not invalidate its Si-basedness any more than diatoms have given up carbon-basedness.
Silicon's near absence from our favored solvent, like iron's, is a product of toxic levels of biogenic atmospheric oxygen. Our early oceans were saturated with iron products, and are now starved of them. There is no reason to assume oxygen would be their favored oxidant.
> There is no reason to assume oxygen would be their favored oxidant
That goes back to astronomy no other option is going to be nearly as plentiful.
> You don’t get to constrain alien life with your preconceptions.
It’s not a preconception it’s the solubility of silicon and silicon compounds. Yes, CO2 and SiO2 aren’t the only option for respiration, but CO2 was and is a near endless supply of carbon and oxygen. Without that growth simply slows down dramatically. Even with a photosynthetic equivalent you simply don’t get the great oxygen event from silicon lifeforms in even 10 billion years.
PS: To be clear I am not saying silicon life would be impossible just that it’s at a huge disadvantage head to head and would have a vastly slower progression to large scale multicellular life.
Relative plenitude did not dictate the elements we and our relatives use, and would not for other life, either. In any case, many other elements are plentiful.
Carbon is a good choice for our temperature range, but there are plenty of temperature ranges as well or better represented. Life will not sneer at the others. Most life on Earth cannot make any use of the carbon in CO2, no matter how much of it there is; in fact, the more of it there is, the worse off most living creatures are, only green plants excepted. You would die in a room with the nitrogen replaced by CO2, despite that you use none of the nitrogen at all. (Only bacteria can "fix" nitrogen, and only some of them.)
Iron is very plentiful in the cosmos and in Earth's constitution, and most life depends on it, but it is practically nonexistent in the open ocean; yet life thrives there. Even where iron is plentiful, life uses hardly any. Silicon is extremely plentiful, too, yet used by our life even less -- until just lately!
So, your argument from plenitude utterly collapses. Life as we know it is a product of history and circumstance. Given different circumstances and different history, you should expect a different product. There will certainly be similarities dictated by physics: e.g., cells are very, very likely, and equally so use of liquids. Aperiodic fibers to encode genes, cognate to our DNA, and others to fold up and carry out processes, cognate to our peptide chains a.k.a. proteins, are quite likely. But there is no reason to imagine that any of the details of the encoding would match.
> Even where Iron is plentiful, life hardly uses any
That’s a huge misconception about biology and evolution. Basic cellular biochemistry is extremely well conserved. There is almost no pressure to use more iron, but significant pressure to use less. Photosynthesis for example is Iron dependent and that acts as a major limiting factor on ocean ecosystems. Yet, we don’t have an iron free alternative adapted to utilize that giant ecological niche. Life is seemingly using as little as possible.
That should suggest why primarily silicon life is such a poor option.
> There are plenty of temperature ranges as well or better represented.
For complex life it’s not just about temperature but also pressure and access to sunlight. Anyway, the normal argument is that silicon based life could thrive in extremely high temperatures. That’s all well and good for silicon but not so much the other chemicals it’s interacting with. Life is dependent on being able to reliably create and break relatively weak chemical bonds. However, when you start to look at the actual chemical options at those temperatures you run into serious problems. The kind of large molecules you want for complex life are either unstable or too stable at those temperatures.
Iron is not the key element in chlorophyll; magnesium is.
We don't know of many interesting Si compounds specifically because we have none of the organisms that would produce them. Our ignorance does not constrain nature.
"Weak", for bonds, is exactly a function of temperature. At higher temperature, life will have chosen constituents that bond with the right strength, wholly ignoring your preconceptions of what it ought to be using.
Chlorophyll contains magnesium, photosynthesis requires Iron at about 1000 magnesium atoms per iron atom. However, Iron still ends up the limiting factor in ocean ecosystems. https://zenodo.org/record/1258477
Anyway, Life can only chose chemical bonds that are possible. It’s perfectly reasonable to pick a specific temperature range and say here this is ideal for silicon lifeforms, but that means every chemical interaction must occur in that temperature range which is a major physical constraint.
We don’t know of many interesting and relevant Si compounds in large part because they don’t exist. It’s not even just chemical compounds life needs a water equivalent for all that cellular machinery to float around in and bump into each other.
Again: Relevant Si compounds don't exist here, because there is no Si-based life here. Our favorite carbon compounds would identically not exist in a Si-based ecosystem. That the useful compounds would not be simple substitutions of Si for C is of no importance. As I noted, some liquid-analog is likely involved in any spontaneously evolved ecology, but it does not need to be water, or even, technically, liquid-as-such.
Nature is not constrained to the limits of your imagination. I am frankly surprised to find you continuing to insist it is.
The tangible existence is irrelevant, computational chemistry is more than capable of exploring this territory. The issue isn’t simply finding giant complex molecules that would make up such hypothetical lifeforms it’s looking for the basic building blocks.
In the end all of chemistry comes down to quantum mechanics it really is quite constrained. Put another way you can list our every possible 2-9 atom molecule containing Silicon plus common elements and look at how the behave.
And, you claim to have not just made such a list, but also explored all of their possible interactions with one another and with what could be common non-Si compounds in their vicinity? You and what ten thousand universities?
You are just making things up. Who do you imagine believes you? Why do you want them to believe you?
"Sorry, no. CO2 being gaseous is a major availability and energy advantage"
At room temperature. Silicon life, if it exists, would be basically using lava instead of water. Glassblowers work at 600 degrees, i imagine thats the sort of temperatures where we will see any silicpn chemistry take place at non glacial pace
Silicon at those temperatures is still not a gas. But more interestingly photosynthesis equivalents become drastically less efficient at those temperatures. Life could still extract energy from chemical processes or even light, but ecosystems would be energy starved which slows down evolution. On top of this the chemistry capable of supporting complex life is again less efficient than carbon based life at lower temperatures.
Net result you might get the equivalent of very simple multicellular life, but intelligence becomes extremely unlikely.
Yet, there are simple Si compounds that are gaseous at such temperatures.
Chlorophyll photosynthesis does not work well at high temperature, but that says less than nothing about whether photosynthesis of different products using a different molecule and a different process could evolve. What we can say is that if it could, it would, somewhere.
You have no basis beyond your own preconceptions for any statements about likelihood. Thus, your estimate is 100% confabulation.
I would say, get your head out of your edge cases. Before I go on, I hope you understand no one is saying its not physically possible, and that it absolutely does not exist anywhere in the multiverse, just that if we come across other life, it will most likely be similar to our own.
by definition, the most probable form of life in the universe is the 1 we are observing. you only need math and probability to figure that out. We also have observational evidence. As far as we can tell, there is no other life in our solar system. We have 8 other planets and many moons that have failed at creating life in any form - that's literally hundreds of billions of years of failed attempts at life.
you can't just pick an element and think its going to work. you need ALL the elements, ALL the states of matter, and the right ratios and amounts of elements to work. Even if you get that lined up, expecting complex life to form under enough pressure to create diamonds in thousands of degrees centigrade also puts the probability of complex life off the table.
I don't known who this is hard to understand. in the simplest example as the article states, if you want to fly, there are things that necessitate something that will fly, such as wings. no wings, no fly. sure its POSSIBLE you can fly without wings, but UNLIKELY. given that we have multiple lineages of evolution taking different paths that end up with the same solution is evidence of that.
The Earth is the edge case, is the point we're making. All of the conclusions and deductions about what life must be like elsewhere that use Earth as their implicit foundation are going to be overfit to the data, so to speak. Organisms on Earth converge to similar forms: dolphins and fish, bats and birds, for instance, so the form is useful on Earth is a valid observation. Therefore, we can expect to see these forms throughout the Universe is a quite a jump.
You do not know that. All available evidence points to the opposite: We have no knowledge, not even a hint, of any other physical process that could sustain life than that of Earth's carbon-based chemistry.
The idea that life could take a myriad of different forms is beautiful, but it is pure fantasy, based on no evidence at all.
>>We have 8 other planets and many moons that have failed at creating life in any form - that's literally hundreds of billions of years of failed attempts at life.
Again, how can you be so certain of it? Life could have existed in some form on Mars or Venus or even Mercury millions if not billions of years ago, only to be extinguished by the changing conditions in the solar system and ground to absolute dust by time. Maybe not advanced space faring civilization, but life could have existed in those places and you simply don't know.
>> you only need math and probability to figure that out.
Yes, and maths and probability are telling me something very opposite to what you are saying. That if you are observing a solar system like ours(forget the entire universe for a second) for a ~100 years out of billions of its existance, then sorry, but you don't know anything about it, certainly not if it harboured life in the past or not, not to a degree that you seem to be certain of.
You don't see a lot of natural hot air balloons floating around do you?
Buoyancy in water is different than in air. Lighter than air natural controlled flight, even in a relatively dense atmosphere like Earth or Titan, is highly unlikely. Fish maintain buoyancy with oil in their livers which is a relatively low energy process.
Hot air balloons and other LTA vehicles work by having a mean density lower than the containing medium e.g. the atmosphere. Even with Earth's relatively dense atmosphere there's not a lot of lifting gases that are effective without significant heating. Definitely not readily made by biological chemical processes. That leaves thermal balloons. The amount of energy to heat the air in a hot air balloon is pretty significant and requires energy dense fuels.
So a hot air balloon animal would need to produce and then burn energy dense hydrocarbons and have a strong yet lightweight natural gas envelope and body structure that could handle the burning of that fuel. Burning I would note at temperatures that would sterilize surfaces.
>>You don't see a lot of natural hot air balloons floating around do you?
Not balloons perhaps, but spiders float on strands of silk using very similar principles.
Pollen and seeds frequently use some kind of floating device to spread as far as possible - again, you probably wouldn't call it flying as such, but they can move through the air for the purposes of reproduction without having wings.
Floating is not controlled flight. Being blown by the wind due to a high surface area to weight ratio is not flight. I move through the air without wings when I walk. I could jump off a diving board and get some forward motion going. Neither are in any way flight.
1. Fish do not, in fact, use oil in their livers for buoyancy. They have an "air bladder", which you may read about. You might have heard something, somewhere about shark livers. Fish are much more closely related to you than to sharks, so it is a big error.
2. Buoyancy in air has been achieved with an industrial level of success using hydrogen. Producing hydrogen is easily within the energetic range of biological processes. Air-buoyant animals could have existed for millions, even hundreds of millions of years before being outcompeted by pterosaurs and birds, and then left no trace.
> Fish are much more closely related to you than to sharks
Sharks are fish, so this clearly isn't categorically true. You probably mean either bony fish (for which I think it's kind of questionable that its true) or more specifically lobe-finned fish (for which the case is stronger.)
Um, my point was that that is arguably true of bony fishes, more clearly true of the narrower category of lobe finned fishes, but not at all true as originally claimed of fishes generally, as that includes cartilaginous fishes (including sharks), and sharks are pretty definitively more closely related to sharks than to humans.
It actually, as written, asserted that all fish have air bladders.
“Fish with air bladders do not, in fact, use oil in their livers for buoyancy. They have an ‘air bladder’, which you may read about. [...] Fish with air bladders are much more closely related to you than to sharks, so it is a big error.” is critically different than what you actually wrote upthread, and is obviously kind of silly. It also would have made no sense in response to the post it responded to, which also referenced “fish” in general and not “fish with air bladders”.
now you have de-evolved the conversation by trying to change the definition of fly to swim. if you are going to do that, there is no point in continuing the discussion. Furthermore, you are confusing buoyancy with flight.
Both air & water are fluids (same equations can be applied to many problems). Equating them in the discussion about aliens is not a step too far which it doesn't require much imagination (compare it for example with an idea of a living nebula that might require some knowledge what is entropy, what is life in terms information, etc)
I disagree with this assessment of silicon based life. While it is true that Earth's crust is mostly silicon, it's also at a temperature that would make metabolic processes using silicon very difficult until you get down to the mantle.
It could be that silicon based life is in fact constrained by temperature and can only arise in planets where the mean temperature is in the thousands. This could in fact mean that we do have a parallel silicon based biosphere underneath our feet. There is obviously no evidence for this whatsoever but then again, there is no reason to assume that the occasional leakage in the form of volcanic eruptions would leave any trace that we could use to deduce that these samples were once living entities.
Doesn't it intuitively seem like the life by definition would evolve out of any particular niche - say 1,000 Kilometers under the surface - to other areas?
I'm at best doubtful about life on Mars because I find it hard to imagine some form of life that occupies a small part of Mars i.e. it's only in the parts we haven't seen. I tend to think if there's any life on Mars it'll find a way to deal with the conditions on all of Mars. By the same token if there's any silicon based life then it'll pop up in places that we can find as well as those we can't. Maybe it does best in places we can't but surely there would be some oddball silicon based creature that would beat the odds.
The macro example would be the extinction of the South American marsupials when the North and South American land masses merged. All the placental animals in North America went south and all the marsupials in South America went extinct. Except for Opossums which for whatever weird reasons not only survived but went into North America.
No because if this was true, then we would see carbon based life do the exact same process in reverse. However, there is a limit to adaptability, particularly through the dumb and highly stochastic process of natural selection.
We have no evidence of a void ecology in near earth orbit or of life persisting close to the Moho barrier - where the crust meets the mantle. There are hard limitations to the encroachment of life that only technology or radically different chemistry can circumvent.
The same hard barriers might also mean that life on Mars is largely constrained to those few underground liquid water lakes that we have recently found evidence for. Keep in mind that even the most barren deserts on Earth have several orders of magnitude more water present in the air than on Mars.
> Doesn't it intuitively seem like the life by definition would evolve out of any particular niche - say 1,000 Kilometers under the surface - to other areas?
Other areas that are similar, sure. But if you're asserting that we can be confident there are no subterranean mantle-creatures because we don't see any wandering about out here, I don't think it's a good argument, for the same reason we can't go down there ourselves and look
If mantle-creatures were to exist, they would have a far, far greater volume of living space to expand into than we surface-dwellers do. Maybe they just haven't gotten around to us yet, for the same reason we don't have any large cities in the antarctic.
What do you mean by “by definition” in that first sentence?
Like, if it failed to do so, it would fail the definition of life? I don’t think anyone defines life that way, and I don’t think it would be a good definition (would I even count as alive under such a definition? It seems like no.)
I think of life as dynamic. There are limits of course - it's taken billions of years for life to operate in the vacuum of space but it really does seem like part of the definition life should be that it spreads. I'm confident that you too move around.
What's the path-dependency-ness of life? Like, once you have carbon based life to what degree does it preclude silicon based life from evolving? How often does a feature evolve sui generis when the nich that the feature exploits is already filled? Clearly it happens sometimes so if you've got a good enough angle you can step into something that's seemingly already covered.
For all that after several billion years it's just carbon based life forms in these parts. You'd think that there must be some area where silicon based life would provide an advantage. Unless it's a case that carbon based life is an overwhelmingly superior product but on some hypothetical world it's simply filled with silicon and there's virtually zero carbon.
Carbon is a way better chemical for life than silicon. It can form vastly longer chains and produces IIROCC (if I recall organic chemistry correctly) much more robust bonds.
Additionally we find organic molecules everywhere from comets to gas clouds in galaxies. We don't really find as much interesting silicon-based chemistry everywhere.
"Other forms of life didn't develop for a reason" isn't that convincing of an argument. We are somewhat knowledgeable about what chemical and physical processes can occur between, -100c to 1500C under 1atm or so, +-100 nanoteslas, in a timescale of under a human attention span. Beyond that, we become increasingly clueless.
We have only a single very specific data point. That, and the human tendency to opine confidently about that which we cannot know.
Well, stage one to silicone life could be computer chips.
Then for a transition period, the shell could be metallic followed by integration of the human mind to that almost indestructible body shell.
Something like the bad guy terminator 2.
But step one could be computer chips. Human designed and made rather than by strict definition of natural selection.
> First off, it it were, given Earth's crust is mostly silicon and its the most habitual place ever discovered, it would have evolved here. but it didnt.
If we assume for a second that silicon life is a thing, would it be reasonable to think that it would be utterly alien? Probably it's chemical composition would be entirely different, but would it be unreasonable, that it could evolve eye, muscle, bone etc. analogs just like us, and the end result would be not entirely unfamiliar to our earthly eyes? The article talked about wings being one of the few viable modes of flight, and Richard Dawkins has made a lecture about eyes having evolved independently multiple time here on earth (like in, as the article states, mammals or octopi).
Octopus eyes did not, in fact, evolve independently. This claim is repeated ad nauseam and is wholly false.
The common ancestor of octopods, insects, and humans had eyes, and coded where to put them with the same gene in all lineages that have eyes. This was demonstrated by inserting a vertebrate "eye here" gene into a fruit fly embryo, causing an eye to grow there.
Weir’s latest book goes into this. (Ex: Audible hearing is based on the distribution of frequencies generated when solid bodies collide or rub.)
On the other hand, If life is that which can use an energy differential to create more order within it (an entropy pump) then sure there are likely forms of “life” out there that we’d have a harder time imagining (that perhaps operate at physical scales and timescales beyond us — thinking nebulae)
> Audible hearing is based on the distribution of frequencies generated when solid bodies collide or rub.
... in Earth-like conditions, and useful in Earth-like conditions. Vibration of denser or rarified gasses could require other solutions to exploit, if it's possible at all
> If life is that which can use an energy differential to create more order within it (an entropy pump)
Now that's the ticket! Under this definition, I suspect most life in the Universe is not carbon based, but far more exotic (to us)
> What creatures would form under an intense magnetic field? In methane? In close orbit around a dim star? In a hot cloud nebula?
Before the question of what you have the question of if.
Then you have the question of continuous constraints. Sensitive dependence on initial conditions still has to operate in a constraint space, and maybe constraints for complex adaptive living systems are much tighter to begin with. Tornados are also sensitive to initial conditions, they are even self organizing, but they are not living beings for example.
Imagination is fine when you’re not burdened by starting a working system from first principles. Conceivable sounds probable when you know less about the constraints.
> Before the question of what you have the question of if.
Meh. I mean, sure, when all is said and done, everything is constrained by physics and chemistry and imagination has no bearing on this reality. On that we agree, to the point that stating it outright is almost a non-sequitur: a true statement that has no relevance to the discussion at hand.
Human culture, in the 400 years of since the first glimmering of the scientific method, has made gigantic leaps in understanding objective truths about our Universe and what lies within it.
At every step, highly educated people confidently assert that we know all that is worth knowing and everything henceforth will just be filling in the details. At every step, these assertions have been a failure of imagination.
I can confidently state with only historical evidence to go by that our current understanding of the Universe is deeply flawed and will be completely overturned someday. Or if not, it would be because we're just not intelligent enough as a species to do it, and not because we know it all*
It is this sense that I mean, when I say that asserting all life throughout the Universe will have forms like those found here, is a failure of the imagination.
* Everything that we ever will discover is constrained by the form of our bodies, our evolutionary history, our psychology, and to a lesser degree by our cultural outlook and worldview. There are truths about the universe that are literally forever beyond our discovering because we are incapable of discovering them.** Were we to encounter alien entities that made use of such hypothetically inaccessible principles, especially if their physical forms were based on them in some way, we would literally not understand what we're looking at.
** As an aside, that is my favorite explanation for the Fermi Paradox, that the interstellar cosmos is thrumming with the signs of life and civilization, but we only partly and minimally understand what we're looking at, and so miss these signs.
On the one hand, the conditions under which some lifeforms are thriving here on Earth are already pretty extreme.
On the other hand, indeed, we may not yet be in a position to be able to imagine, realistically, all that we would (eventually) agree to call a lifeform. (Life built from phonon "particles" in a planet-size crystal, anyone?) Sure, there may be constraints, such as life, in a meaningful sense, may only be realizable based on polymers, in which case the conditions must be such that they allow polymerization of simple substances to take place.
> On the one hand, the conditions under which some lifeforms are thriving here on Earth are already pretty extreme.
Not really. They are all within +/-5km of the planet surface, live under 1g of gravity, as a rule, are not exposed to X-rays, gamma rays, cosmic rays, strong magnetic fields or nuclear radiation, or extreme temperatures. There's nowhere on Earth that receives more than about average solar radiation or gets much above 100C where life survives.
Life generally has access to ample oxygen, though a few anaerobic organisms exist. They're all DNA-based, have access to ample amino acids, aren't bathed in thousands of completely toxic chemicals, have liquid water (and not, e.g. liquid methane). The list goes on and on.
Yeah, there are a few extremophiles, but they are by far the minority, and are clearly adapted incrementally from other organisms that evolved in non-extremophile environments. In essence, there's a large reservoir of easy-pickins living that generates biodiversity to cross over into extremophile environments.
Now imagine 5x the gravity, 100-1000x the solar irradiance, the lack of magnetic field (and thus direct exposure to solar winds), no atmosphere, or atmosphere entirely composed of a toxic gas, extreme exposure to X-rays, etc. The universe is full of many places where Earth life, even extremophiles, would have no chance of survival. And such places don't have reservoirs of biodiversity from which to adapt to these conditions. They're just dead.
Extremophiles are in no sense rare. They constitute the most diverse collection of branches of the tree of life. We are on one of those.
This is not accidental. There is more genetic variation in humans in Africa than the whole rest of the world, and more variation in English dialects in England than the whole rest of the world. We -- everything we knew existed until recently -- evolved from extremophiles. They came first. The world changed around them. Some changed to match, eventually giving rise to us, while others found places more like what they were used to. The latter are still to be found in those places, and in many others they have also adapted to.
Common types like us are adapted to currently common conditions. When the environment changes radically, and all the life we knew of up until recently is extinct, the extremophiles will radiate a new ecosystem adapted to new conditions.
We have exactly one example of an environment that nurtures life. It does not logically follow hence that it is the only environment where life can thrive (unless we choose to define life as that which thrives in an Earth-like environment)
I do agree that probably most of the Universe is hostile, not only to Earth-like life, but to life of any definition. But we cannot be certain. We have never visited nor sent a probe to a 5g planet "100-1000x the solar irradiance, the lack of magnetic field (and thus direct exposure to solar winds), no atmosphere, or atmosphere entirely composed of a toxic gas, extreme exposure to X-rays".
I'm actually in agreement with you. Those places I mentioned probably do not have DNA and amino-acid based life that looks anything like Earth, particularly because those environments eviscerate the delicate chemistry necessary for that particular system to work. So life would look totally different.
I'm more of the "Boltzmann Brain" persuasion. Life might take the form of electromagnetic waves or metallic structures that are respirating, self-replicating, information-processing things. In my more paranoid days, I think the internet is alive, as it is kind of like a life-form growing our the substrate of our collective digital actions.
Didnt they find life where no one was expecting it to be? (Dark bottom of the sea, under intense pressure and surviving on vents). Deep sea creatures also look really alien. Might be a clue of the "weirdness" we might find out there
> (Life built from phonon "particles" in a planet-size crystal, anyone?)
It seems unfathomable to me that life could be composed of bosonic particles, since Pauli exclusion seems to be one of the most important reasons why matter (never mind living organisms!) has the property of spontaneously structuring itself in a rich and complicated way.
Agreed. At a bare minimum, human thought patterns have to be rare. At some point we're either going to murder ourselves or create a Von Neumann machine capable of interstellar flight. After that humans or human-derived machines will fill the universe. Since that obviously hasn't happened with alien machines, the aliens are either not alive or totally unlike us.
I don't agree that human thought patterns have to be rare, or your other assumptions. The only safe bet in this discussion I think, is, we don't know anything for sure.
> At some point we're either going to murder ourselves or create a Von Neumann machine capable of interstellar flight.
There are many, many possibilities for human futures that are between those two and not do extreme. It is absolutely possible we survive millions of years without interstellar travel or self destruction.
> Since that obviously hasn't happened with alien machines
I also think it is not so obvious that this hasn't happened or isn't happening with alien machines. It certainly could be and we would not know either way. A la 2001: A Space Odyssey, perhaps in fact we are a product of alien machines themselves.
There is a book Accelerando by Charles Stross that talks about why neither case might be true - he shows a scenario where life ultimately transforms its host system into a matrioshka brain. At that point distance from the cloud is reduction in bandwidth to the parts of yourself that exist in that cloud- if the matrioshka brain can simulate billions of planets and leaving it makes you incredibly stupid by your normal standards why do it?
Because if you don't, someone who does is going to invade for energy and resources. Therefore, refusing to expand is a slow form of suicide, unless you can be somehow certain there's no entity like that in the potentially accessible space.
At some point growth in any star system is going to be finished - energy extraction near maximum, no free matter left to convert into computronium. After that, only two solutions remain: stagnation (death) or expansion. Assuming no instant communication (not just FTL - instant), the bandwidth argument only means it makes more sense to haul energy and computronium from the rest of the accessible space into one point.
We may very well already see it somewhere far away, thinking it's "natural" rather than a construct.
I think under current knowledge the most likely prediction is something resembling a sphere (minimizing distances between points) that utilizes black hole power plants, feeding them matter from stars and nebulae.
From the outside, it would look like a giant void with nothing in the center. Maybe there's something like that in the center of the Boötes void?
> Because if you don't, someone who does is going to invade for energy and resources. Therefore, refusing to expand is a slow form of suicide, unless you can be somehow certain there's no entity like that in the potentially accessible space.
I've heard that described as "where are the supernova defense systems?" Of course, I'm not aware of any explanations for why it's physically impossible to have a relatively small system sufficiently "hardened" to survive a supernova, or perhaps a way to defend oneself (including hiding) that doesn't require stasis.
Accelerando is a great book even if his writing style is a little dry. The mass of one planet being able to simulate billions of planets is only possible if the simulation is rather poor. You can't create a perfect simulation like that any more than you can perfectly simulate seven atoms using three atoms. Computation is never going to be more efficient than physics.
why do it?
Everyone doesn't have to do it. Just one person out of billions does. Think of the strange and perverse collection of behaviors we observe in a population of a few hundred million people online and speaking English. Expand that to billions of hyperintelligent minds and somebody is going to want to colonize the universe.
I agree about the writing being dry. Honestly I couldn't finish it, it felt more like a series of interesting future wikipedia articles than a novel. The problem is sometimes those interesting wikipedia articles will be in between about 50 pages of sci-legal-fiction describing a legal ecosystem where sentient corporations are conducting some kind of mysterious magic future economics / ecology that is never actually described.
But anyway back to the discussion:
>The mass of one planet being able to simulate billions of planets is only possible if the simulation is rather poor
The mass of one solar system! And you don't need to simulate the system to a planck length. In fact the book specifically addresses that scenario - different simulations have different planck lengths and planck times, depending on the needs of the users of that simulation. For most users (certainly your average modern baseline human) that length might be on the orders of fractions of a mm, and some users might not require a physically meaningful interface at all!
>Everyone doesn't have to do it. Just one person out of billions does.
That's assuming that the culture doesn't have significant bans on von-neumann style self-replicating machines. If they allowed such devices of course you'd expect an expanding light cone of computronium around every significantly advanced culture but any sane long-lived culture would recognize that such machines are just about the only existential threat that a culture with those capabilities would face. That might significantly limit the 'explorer' class to those entities willing to do the equivalent of taking an ice pick to the frontal cortex in modern humans in order to undertake a multi-multi-millennia solitary journey into the void. Some fraction of those trips would fail, and the successes would take a non-trivial amount of time to launch another. Maybe those growth rates are smaller than we would suppose and the universe has only had stars capable of producing the elements of life for a little while on a universal scale, maybe those light cones just haven't reached this corner of space yet.
> At a bare minimum, human thought patterns have to be rare.
Definitely. In fact, I think they are almost certainly unique in our entire local galaxy cluster, and we will never find anything even close.
We could very well find something interesting, enlightening, sophisticated or using what we might be able to squint and call technology, but I suspect we will never find an alien civilization intentionally broadcasting for example the fibonacci sequence or prime numbers so that we can learn to exchange culture and communicate ideas.
> At a bare minimum, human thought patterns have to be rare.
I'm not so sure. We can't even be sure if cetaceans, in particular orcas, have thought patterns similar to ours. Of course, they lack the physicality and environment to develop written history and knowledge and also technology, but we currently have no way of knowing what their thoughts are.
Agreed. How then could we expect to exchange views with an alien species, when we cannot do the same even with Earth species? We imagine it would somehow be easier if only the alien species were "intelligent", but then our expectation arguably defines intelligence in No True Scotsman terms, essentially an intelligent species is one with which we could communicate.
Most would argue against a species being intelligent if we could not communicate with it. "These are just automatic processes, like sophisticated software"
> Could we even recognize them as alive, much less intelligent?
If we focus on recognizable features, we may look for organisms with self-replication skills (a feature of living organisms) and prediction skills (a feature of intelligent organisms).
On the intelligence aspect, the skill to predict the future in general, and imminent threats in particular is useful for structured organisms less resistant than rocks to survive. On that matter I wonder, do unicellular organisms on earth have prediction skills?
What also helped those fragile structures to continue existing along rocks after a long time might be their ability to replicate themselves before being destroyed. Reproductive skills might actually be the first interesting feature to look for in extraterrestrial organized structures.
> we may look for organisms with self-replication skills... and prediction skills...
Sure, but I imagine this is easier said than done. We 21 c. humans would be most likely to recognize as intelligent life something obviously not a natural feature of the landscape, that operates on a time scale under a year and above a split second or so, that predicts that which we can predict, and most importantly has a form corresponding to Earth creatures. Without ticking all those boxes, especially in a truly strange chemical environment, we will have people asserting that they are a complicated chemical processes, but in no sense alive the way we are alive, if we can even recognize them at all.
Of course the environment will determine life forms. What the article says is that if there is a gaseous atmosphere, for example, then selection will reward animals that are able to move through it. That means for organisms that are heavier than the surrounding atmosphere - most likely - wings. For liquid environments, there probably aren’t that many locomotion techniques that are both effective and missing on earth, meaning when we see something swimming in water on a different planet it’ll look like a jellyfish, octopus, fish, worm, clam, bacteria, shrimp, horse… or one of the other hundreds of ways of swimming
Once we move outside Earth-like conditions, we should be decreasingly confident about our speculations, not more confident. What are the chemical and physical conditions of a hydrocarbon lake at 5g, -180C, 1 kilotesla and 100 atmospheres? Can we really be confident that "whale" is the best mechanical solution for moving around there? Can we really be confident that "moving around" would even be the best survival strategy? I think not.
Indeed earth evolutionary processes require earth like conditions. But here I mentioned swim in water which is a pretty strict constraint on temp vs pressure.
That said even in any other fluid I doubt we’ll ever look at an organism and say “it swims like …<blank>“ because there wasn’t an earth organism that swims anything like it. Of course that means comparing to every method of swimming locomotion on earth which is a staggering diversity from the microscopic up to whales.
Unless other forces are involved (e.g electromagnetism isn’t used for locomotion on earth to my knowledge) and the fluid is incompressible like water, then I’m (armchair) guessing “to swim” doesn’t have that many evolvable solutions, regardless of pressure/temperature and the specific chemistry.
>There's an entire genre of these kinds of books that extrapolate generalities (life throughout the Universe) from a single data point (life on Earth), but the truth is, that's not even an educated guess.
Hey, whatever sells a pop science book pounded out over a long weekend.
It's funny how sure everyone was about slowing expansion of the universe and the idea of close rocky planets/distant Jupiters, but only lucky guessers are remembered.
It could simply be that patterns for lifeforms on Earth were set so long ago that everything sort of rhymes. Veer that path at the beginning and you end up with a significantly different answer.
Nah. Think of fish - and the assertion "There's no such thing as a fish." That refers to the similar evolution of many branches of life that ended up "looking like a fish" but are otherwise unrelated.
They had a common ancestor of a coral-like sea squirt (If I remember right). That looked nothing like a fish.
Koshkin, theyellowkid, I, and whoever else thinks aliens are probably profoundly weird: drinking and coming up with increasingly outlandish ideas for aliens. Now that sounds like a party.
We humans have only our definition of life form. These are limited by physics and our logic.
However, we can't even see the whole universe, with no scientific break through, we never will.
We don't exactly know the full story of the big bang, we can't explain the very beginning.
We don't know what happens in black holes, our logic rules literally breaks down there.
I could well be that there are life forms which we couldn't even imagine, which are not limited by our known physics.
We know a little bit about space time and gravity and the elements.
Dark matter still unexplained, no universal formula for everything in sight, i have seen DNA mentioned, maybe some creatures do not need any DNA.
Too many factors are unresolved, we don't know whether there have been, are or will be totally different species.
Imagine, at one point in history, earth didn't even exist, before animals, there were only bacteria.
Earth lifetime is nothing on the grand scale of things. Humans are a more intelligent version of very common mammals.
With a couple more things gone wrong, like a flu or smarter predator animal in the past, humans might have never come to be.
I greatly appreciate scientists and people discovering and accumulating the knowledge, and I understand the scientific methods have to be followed accurately, else we diverge into pure speculation.
But limiting possible alien life to earth like planets might not be all there is.
> The universe could possibly avoid eternal heat death through random quantum tunnelling and quantum fluctuations, given the non-zero probability of producing a new Big Bang in roughly 10^10^10^56 years
I used to explain to myself what was before the universe - that it simply didn't exist, just like myself didn't exist, but in fact my body is a continuation of life since its inception - like my parents knew their parents (or at very least they had a brief contact with their mothers), their parents knew their parents and so on back to something that sparked life, but that something also must have come from something. So still can't get my head around what was before the universe.
I know these visualisations that show for example that something that has beginning and end can be divided infinitely, but when I picture it, this exists in some sort of space.
I expect that there are some things that are "universal" and some that aren't.
For example, if life--any life--forms on a planet, it is likely that some macro-organisms will evolve that consume other organisms.
On Earth we have plants that are eaten by animals that are eaten by other animals and so forth and these all act as a form of "battery" in that solar power is converted into energy and increasingly stored in larger "blobs". This is almost necessary for large life to exist. Well, for carnivores at least (eg many whales eat krill and there are a bunch of filter-feeders).
So the chemistry of life elsewhere may be similar or it may be totally different but something like a carnivorous trait is I think almost inevitable.
Once you have that then certain other traits became almost inevitable. Flight, for example. It may be that flight is impossible given local conditions (eg high gravity, atmosphere or the lack thereof). That doesn't mean we'll end up with feathers and birds per se but evolutionary pressure will likely mean available niches are filled. On Earth almost every environment has life, only really excluding the coldest, driest, highest and deepest of places.
Also, consider sensory organs. I expect the ability to detect parts of the EM spectrum, sound, taste/smell and tactile feedback will all likely evolve with sufficient time. And that itself has consequences for what life looks like.
Great read, thanks. This is a very interesting subject to me. A couple of years ago I read a theory about alien life that was a bit different from this:
Given the age of our universe, sun, earth and humans:
Universe 14 000 million
Sun 4 600 million
Earth 4 550 million
Earth Life 3 500 million
Humans .2 million (200,000 years)
The probability of some alien life being within say, a range of [-.5 mllion, .5 million] of the life on earth is VERY slim. It is most likely that life out there is either in very early stages (protezoric) or that it is way farther than our current form (how will humanity look like in say, another 500,000 years?, assuming it continues to exist and evolve)
First, the article wasn't about human-like technological civilization, but just about life in general. And there are species of animals alive today that have hardly changed in 100s of millions of years. So Kershenbaum would be right if we found some life-forms that vaguely resembled for example a Coelacanth on some exoplanet.
Second, you're ignoring the fact that life as we think of it can really only evolve around at least 3rd-generation stars because you need enough heavy elements. That cuts the age of the "life-capable" universe by at least half, so the window of relatively modern life on earth with respect to the age of the life-capable Universe really isn't that small... let's say 350My out of 7Gy, so about 5%.
Stars that formed in nebulae that had 2 previous cycles of star formation and super novae.
This means that the star’s solar system at that point has sufficient quantities of heavy elements which cannot be produced by stellar fusion, as these elements are produced by super novae and from solar radiation.
Basically all the neutrons that are produced when a star goes boom create the elements that are above iron in the periodic table.
First generation stars are stars that are formed from big-bang gas - mostly hydrogen, a bit of helium, a trace of lithium, and nothing more. Second generation stars are formed from the gasses blown off by the novas of first generation stars. Third generation stars are from the novas of second generation stars.
I suspect that the claim that life as we know it can only evolve there is because life as we know it needs a wide variety of chemical elements. We need carbon and oxygen, of course, but also iron and calcium and magnesium and potassium and so on. You're not going to get that around a first generation star. You might not get enough of it around a second generation star.
can by products of first gen / second gen star creates life-form that is alive in whatever sense we think something is alive, but radically different in whatever capability we think a life form must have ? What is alive in the sense for us to search in universe ?
First gen unlikely unless life can form from the elements created during the Big Bang and w/e minute amounts were created due to solar radiation during the life of the star.
And most importantly first gen stars can’t form planets other than gas giants and even gas giants are questionable because our current understanding that other than a few failed stars these also usually require a heavy element core as a seed.
2nd gen stars are a possibility in a region of space that had a lot of 1st gen stars to nova and there might be sufficient amount of heavy elements already there to form a solar system.
So unless life can form from hydrogen, helium, lithium and beryllium then no life in 1st gen stars.
2nd gen is highly dependent on the region of space although I would posture that any region active enough to create sufficient amount of heavy elements would probably remain too active during the 2nd generation for life or at least complex life to form.
Familar higher orders of complexity emerge far easier within systems with more states.
Due to our physical laws elements with larger rooms for reaction via chemistry are familar.
The chances of a replicating agent just anthropologically emerging from the surface of a 2nd generation hydrogen dominant star with an accumulation disc composed of little higher orders elements is inconceivably less likely than the relative petri dish organic molecules provide.
Unless we just happen to have evolved very early on compared to what's normal, we should expect a lot of intelligent life with just a little bit of variance on these numbers. And some of that could easily be millions of years old. Interestingly, even if a life form populated new solar systems at a rate of a thousand years per system (where each populated solar system in turn populates more of them), they'd still fill up the Galaxy in only a couple million years.
Unless "intelligent" life inevitably renders its local environment uninhabitable and collapses in short order - a proposition looking more likely by the day. It may be that the intelligence required to maximally exploit the local negentropy is strictly less than the intelligence required to not do that, despite being able to. Indeed it's difficult to see how the trait of "behaving responsibly with an entire planet" could evolve - the selection pressure is rather all-or-nothing.
This is my belief as well, although slightly different in how I phrase it: humans are incapable of seeing much beyond their own selfish desires, and as a result will wind up causing their own extermination. The denial of death is widespread and understandable: to truly consider existential demise is exhausting, and I suspect has been backgrounded for simple evolutionary reasons.
Regardless, the species is naturally incapable of averting averting crises that are foreseeable but distant.
Why is intelligence seen as some inescapable playbook of evolution?
Evolution has no agenda or goals, other than to select for survival. Most species on this planet have a low intelligence yet are successful, and don't seem to evolve into the direction of intelligence.
For every planet with intelligent life, there could be many more without it, no idea what that relationship might look like. I'm not suggesting it's the norm.
That makes it sounds like it took 1 billion years for life to form. According to timelines I've read about (based on scientific papers) it took around 800M-900M years for the heavy bombardment to stop, and temperatures reduced similar to those of today. So once an environment friendly to life appeared, life appeared quickly.
The preferred chirality of organic molecules could absolutely have arisen by chance, but it's an interesting to see this in meteorites.
On the unrelated subject of handedness, I saw an interesting thread on Twitter today [1] speaking about how we're starting to synthesize reverse chirality polymers and enzymes, most notably DNA and replication enzymes.
There are a lot of interesting implications.
You can't get rid of L-DNA without reverse DNase, leading to an accumulation of information and transcription. So they need to remake all the enzyme steroisomers.
That alone is interesting, but you can take it further to the limit and produce reverse biology that synthesizes reverse sugars that can't be metabolized by much of extant life [2]. Suddenly a lab-escaped reverse autotroph can out-compete all of us right-handed lifeforms because nothing can eat them. Bacteria, plankton, the entire food web collapses. When we have nothing left to fish or farm, we die too.
Never thought nanotech's grey goo was plausible. Now I see something that rhymes with it, and I could see it happening within our lifetimes.
It'd make a crazy MAD bioweapon on par with or potentially worse than nukes.
> Such negative values occurring shortly after the GOE require a rapid reduction in primary productivity of >80%, although even larger reductions are plausible. Given that these data imply a collapse in primary productivity rather than export efficiency, the trigger for this shift in the Earth system must reflect a change in the availability of nutrients, such as phosphorus. Cumulatively, these data highlight that Earth’s GOE is a tale of feast and famine: A geologically unprecedented reduction in the size of the biosphere occurred across the end-GOE transition.
A MAD weapon like that just becomes an AD weapon. A nuclear lab leak kills under 1,000 people. A living weapon lab leak would kill (nearly) every other living thing.
Water, sunlight, carbon sources, phosphorous sources, nitrogen sources. And any additional think they have enzymes to break down and process. Advanced organisms could feed off complex organic molecules, but this isn't necessary.
The point is that with reverse chiral sugars, polymers, etc., they wouldn't be a meal for anything in the wild. (At least not one with nutritional value.) No predation and no competition leads to massive expansion, and they could exhaust resources that other necessary parts of the food web require.
Oh, I get it now. And then when they expire they deposit undigestable material in the soil, capturing carbon and eventually turning into coal. The dawn of the dextro-carboniferous period.
This would make a fantastic "phase one" alien bioweapon to aid in wiping out a planet's existing lifeforms and replace ecosystems with one better matching their own. Assuming post-biology aliens care about biology.
The first type is incidental: we've already encountered meteorites from Mars and the Moon, for example, so it's not hard to imagine life bearing material arriving that way.
The second would be intentional: either ET seeds planets or merely visits them with contaminated boots or probes.
Either way, we would pick up some DNA from offworld.
I don’t want to speak for the OP but I read their comment as “why did they evolve certain features that wouldn’t have be reasonable given the evolutionary pressures of earth?” E.g., their ability to survive high levels of radiation or vacuum.
There’s some speculation that a large amount of their genetics were transferred from other animals.[1] I wonder how much this muddles the tracing through the evolutionary tree.
> E.g., their ability to survive high levels of radiation or vacuum.
If I recall correctly, the tardigrades (and extremophiles like D. radiodurans) have evolved to handle damage brought on by desiccation. As a fortunate side-effect, this general robustness also protects against radiation.
What would be the odds that other planets/habitats have a similar "tree of life"? I don't know. Given the huge number of similarities in DNA, I'd say it's extremely small.
His article completely ignores the possibility of engineered life. Engineered life can bypass evolution and natural selection, even if the species responsible for the engineering was a product of evolution.
Heh and what if the engineer even introduces evolution and what he truly engineers is code-based chemical cells that can conquer, survive, evolve and expand from anywhere ? :D
I'd do a life myself, I'd make it post-metallic, post-silicon, post static: I'd make it use water and carbon, so that it can exist everywhere. I would make it so that it can become intelligent on a small time scale, say a few billion years, all on its own, from scratch, on any rock :D
Not saying we have an engineer, but you think of engineered life as you are now as a simple software programmer. But an engineer in 500k years trying to expand more, would probably think of chemical automata that can evolve and adapt in harsh conditions. Say for instance if humanity decided it would be enjoyable for life to exist on Jupiter. It'd have to make something that can try a lot of variations with a very simple first formula to consume whatever gas there is there and survive whatever pressure.
Engineered life still follows evolutionary pressure and natural selection it just might not hit the same walls as life that is only driven forth by random mutations and opportunistic gene exchange does.
Strong arguments can be made that the ability to become a multi-planetary civilization requires you to master the tech tree that includes engineered life.
The first life we encounter from another civilization might not be evolved at all. Presumably a civilization with the capability of interstellar travel might also have the technology to manipulate the underpinning of life itself.
In fact, if we do discover something from another civilization, it is quite reasonable that it would be some sort of Von Neumann probe. It might be made of mechanical parts, "biological" parts, or something in between.
A Von Neumann probe would be highly engineered, and might have no trace of evolution to it.
I recall a scifi story by Stephen Baxter where a human-made probe on Mars eventually evolved into advanced, aware, spacefaring Von Neumann probes. After a few million years, one curious probe traces serial numbers back to Earth in search of their creators. However, humans had devolved back into a type of monkey that was directly symbiotic with a literal tree of life. The probe concluded that such a primitive creature could never have developed technology, and left.
>> A Von Neumann probe ... might have no trace of evolution to it.
Except that the very fact that it exists represents many evolved traits. If they are sending probes then their are either curious or expansionist, both evolved traits tied to competition for resources and/or survival. A species totally devoid of any history of evolutionary pressures wouldn't act that way, which is one of many possible great filters: once we have access to the infinite resources of space, perhaps we just stop caring and don't bother expanding. Such logic allows us to learn much simply from the existence of an otherwise silent Von Neumann probe.
But when dealing with infinity, we must appreciate the likelihood of the unlikely too.
Personally, I favor the prospect of the insanely lucky idiot race, that clumsily and completely by chance manage to launch a probe so seemingly sophisticated that every sentient race that discovers it readily submit to its perceived superiority.
There are no real infinities. The universe might be infinite, but the bit of it we can see and/or ever interact with is not (speed of light + expansion). So there are a finite number of stars that we will ever be able to touch before the universe goes dark. And the universe seems to have had a finite starting point. So we can calculate which stars may ever reach out to us. These are very big numbers, but they are not infinite.
Unless star trek is real. Faster than light travel opens up the door to infinities.
Some forms of FTL travel also opens the door to time travel, so even if there is no multiverse and our universe has a point in its future where all energy is at its lowest possible state, we could still bounce around between the Big Bang and the heat death for quite a while.
Well also, a Von Neumann probe is a type of life. It's very unlikely that a self-replicating machine would not develop it's own technological drift in the replication protocol.
Not only that - for all we know a biological civilsiation could have existed 3 billion years ago which then spawned a machine civilisation that now has as much relation to its distant origins as we do to some prebiotic soup on Hadean earth.
> It might be made of mechanical parts, "biological" parts, or something in between
Or just a digital clone of a once-biological being that can live for infinity exploring the Universe. Why would you explore the Universe in a meat suit?
Or it could be designed to be very small so as to efficiently send out at near light speed, and designed to quickly adapt and replicate in any hospitable environment.
Unless it somehow came from nothing, then there must be some pathway from what came before to what they have now (thus evolution). It might be a long pathway, which is so long that it's hard for us to see the beginning from the end, but that doesn't invalidate the argument that it will still have characteristics of something that followed such a pathway.
If Star Trek taught me anything, it's that most aliens look like humans, except for some bumps on their forehead. Hodgkin's Law of Parallel Planetary Development.
Star Trek TNG kind of lampshaded that in "The Chase", where its is revealed that alien species are similar and biologically compatible because they share a common humanoid ancestor.
I read somewhere that the most likely "alien" visitor is a bacterium, virus, or other organism that rode here on a meteor fragment. That achieves interstellar travel without the need or intelligence or intent. It was also the subject of the terrific movie The Andromeda Strain.
Perhaps it evolved on a planet with an Earth-like, but much harsher, environment.
To draw an analogy from fiction, what would happen if one sent Giger's Alien in all its glory, razor tail and all, to compete in an entry-level boxing match? The Alien has no rules, has acid for blood, tongue-crushes the skull of the referee, and so on.
Yeah, they got vented into space et cetera, but I'd say in the first 2 movies humans actually failed to kill the xenomorphs (eggs on LV-426 and aboard Sulaco). At the end of the third movie the newly born xenomorph queen clearly dies. However, in the fourth movie the xenomorphs are again brought back through cloning.
Also, in "Prometheus" and "Alien: Covenant" it becomes apparent that the original crashed ship on LV-426 in "Alien" was not one of a kind, there were tons of ships carrying the gooey secret sauce of xenomorphs.
Also, at the end of the second movie the queen xenomorph was simply vented into space, but whether it died or not was not very clear. I mean, the xenomorphs seemed to be quite resilient and not too picky about things like atmosphere and cold temperatures.
Anyway they were specifically designed to attack humans, and to operate in a human-rich environment; and when there aren't any, to wait around for one to come along and stick his face in just the right place.
This is interesting, and I have a more mathematical way of thinking about this.
If we were somehow able to segment evolutionary pressures, and normalize their values such that they sum to one, I'd hypothesize that as the average evolutionary pressure goes to zero (meaning high number of evolutionary pressures that are generally uniformly distributed), then this author's hypothesis is true. But as the average evolutionary pressure grows (fewer pressures, or highly skewed distribution of pressures), I imagine it would lead to VERY different looking life. I'd also hypothesize that as the average value increases, it leads to system instability.
> there are certain things we can still say about them with reasonable certainty. Topping the list: They evolved.
This is far from certain. They can be designed by someone who was designed by someone who evolved, for example. The evolved life forms may be extinct for millions of years.
Even simple life forms on other planets may be designed, e.g. for someones (analogous to) amusement.
Follow-up: Earth is at a tipping point right now. So far life has been governed by evolution. But within a short time (≤10,000 years, say) it will likely be possible to simulate a human brain quite cheaply. Then things will get weird quite quickly. See Robin Hanson's book about "Ems."
For these reasons I think we can expect that aliens really will be quite alien to us.
I hope that also applies to the evolution of morals for intelligent lifeforms. I think it's safer to assume any aliens will have bad intentions but maybe any lifeform that can build interstellar technology has come to the same conclusions that we (albeit slowly) are coming to.
I don't think any sophisticated intelligent beings could evolve without their primary social interaction being cooperative. You can't build a spaceship if you don't learn to get along with others. You wouldn't evolve complex thought or even language without social pressure. This doesn't necessarily automatically translate to cross-species cooperation, or even intra-species, as evidenced by our own history of wars and subjugation, but in the grand scheme of things, our baseline is trending towards more peaceful existence. I expect the same pressures that would make aliens follow the same form factor as us would also drive them towards similar social constructs.
I have a somewhat less optimistic view about your points of view. The humans and most of the successful creatures on Earth are terrific natural born killers.
Cooperations in humans has emerged only as a way of better milking of resources from otherwise dangerous environments for one individual-at-the-time endevour of surviving.
The evolution of complex thought on Earth had a lot to do with other species competing with humans for food, and simultaneously hunting humans as a food source.
I share your opinion about not automatic cross-species cooperation, but baselining to peace is not what's happening on our society of speaking predators, most of the order (in the whole planet), of the apparently peaceful society, is being continously kept by sheer force or menace of inmediate violence retribution (nation-states, others).
I.E. You could turn-off the lights of big city for a couple of days and few will have doubts about a tragic outcome.
As we are the only society of intelligent species (at least, we are speaking folks), we know, we should be carefully analyzing those facts when hypothesizing about alien intentions.
Indeed, all we can do is conjecture, there's not much evidence to go by. And given a practical question like "should we try to make first contact with unknown aliens?", best to not take the risk. But while we are just conjecturing, it seems intuitive that society and intelligence could in general lean toward peace and kindness. With intelligence comes empathy, and increased understanding - although it's born out of a ruthless and cutthroat evolutionary process, it seems to have its own goals that you can't easily equate to that of other species in the animal kingdom (mammals might show kindness, and empathy even to creatures outside of their species but it's a little easier to see the evolutionary benefits than some very unevolutionary human behaviors).
Turning the lights off in a big city will revert us back to our base/evolutionary goals - so perhaps we better hope these aliens aren't too desperate!
> You can't build a spaceship if you don't learn to get along with others.
We literally built rockets and started spacial exploration out of a pissing contest. It has been clearly on mankind history that we don't need to cooperate as a unified peaceful race to advance technological progress.
I think it’s safe to assume any highly evolved alien species will have moral constructs that support self-preservation.
Whether those morals extend to preserving other intelligent life forms (I.e. humans) seems unlikely since the prosperity of other life forms will inevitably lead to more competition for scarce resources.
The fact that human moral constructs apply to other intelligent species seems to be a bug that arises solely from the fact that we’re currently capable of out competing all other intelligent species.
This assumes that the hypothetical aliens draw (ultimately artificial and arbitrary) distinctions between themselves and other intelligent species. Who knows, they might consider us, another intelligent species, to be 'one of them' in some sense and thus deserving of protection.
1) Not really scarce on a galactic scale and 2) if different species' chemistry are radically different (and why wouldn't they be?) there wouldn't be competition even if habitable planets were scarce.
My optimism says that radical consensual transhumanism might be a universal Schelling point and that if humanity reaches that point we'd fit fairly well into any advanced alien culture that reached the same values. Probably the biggest value difference at that point would be the morality/consciousness thresholds for tiers of personhood.
I don't think any morally advanced culture would be willing to accept an indefinite policy of "live and let live" between the cultures as a whole; there are some injustices (slavery, murder, torture) that wouldn't be tolerable to exist in the known universe.
But that raises a moral conundrum of interference with an alien culture’s development and impact on their world. On Earth, intervention in other societies has not gone over that well. If you have relatively equal societies in terms of technology, then you risk devastating warfare.
It's definitely a moral conundrum as evidenced by the U.S. civil war, the two World Wars, and some interventions in genocides, contrasted with the lack of intervention in other genocides or in Soviet and Chinese (to pick on the largest) mass murder/starvation of citizens for political reasons.
I agree that equally powerful societies face the hardest choice; whether to risk everything to save everyone or to knowingly allow atrocities to continue while preserving themselves.
Seeing how alien ctenophores seem, despite having evolved here, the thesis seems shaky.
Aliens will probably eat, breathe, see, smell, and hear, but might do it in ways that would fail to qualify under definitions we can write based on life we know.
And they will probably have processes and senses we don't, or even just don't yet know any earth creatures have.
Light, pressure waves, chemical compositions, temperature, pressure, body position, magnetic field, distance (sonar) -- what is there around us that some life on Earth is not already sensing? What other senses could aliens have?
We never would have even looked for a magnetic-line slope-angle sense without inventing compasses, and then also understanding the structure of the earth's magnetic field. Likewise, we only understood echolocation after we invented it; before, we had no clue any animal used it. Octopods have no sense of joint angle. Some bugs taste what they walk on.
Thinking the only interesting phenomena in the universe are ones we already know about, or know something useful to do with, is akin to the fundamental failing of TFA.
Soviet writer/philosopher Ivan Yefremov (probably, the most influential soviet Sci-fi writer) argued rather convincingly, that humanss have ideal body size and layout for intelligent beings, and that extraterrestrial life would probably look somewhat similar.
The article mentions that we have 4 limbs only because the creature that left the sea had 4 fins. It could easily have been 6 or 8. He makes it seem as though 4 was just plain random.
One thing I've found fascinating is how the outside appearance of a human body repeats the number 5; there are 5 things sticking out from a center mass (2 legs, 2 arms and the head). Each foot has 5 toes, each hand has 5 fingers. And in the head are 5 outward-facing holes: 2 eye sockets, one nose/mouth hole and 2 ears.
Having more limbs is less efficient biomechanically - the creature would need a larger heart to pump blood through al organs, that requires more energy, so such creature would need more food.
Now, it is known that creatures can lose limbs through evolution, but never gain them, so it is likely that multi-legged species would gradually lose extra limbs over time.
They are aquatic species. When you remove the necessity to support weight above the hard surface, your options are much more varied. Even jellyfishes or amoebas somehow manage to get by.
Early creatures had mady different body plans. We have 4 (all vertebrates), 6 (insects), 8 (arachnids) and multilegged creatures (millipedes), as well as legless creatures like snakes (who had 4 legs before they lost them).
It seems that vertebrates have certain period when this layout was 'cast in stone' [1]
Reading your comment made me wonder why we have even numbers of limbs for different body plans. I realized it's due to bilateral symmetry for most organisms must some how be advantageous to asymmetric body plans, but I'm unsure how symmetry is advantageous. What are the evolutionary pressures selecting against asymmetric body plans?
I'm not really a biologist, but I think this has something to do with the balance: when you move in some direction, it would be extremely disadvantageous to have one side significantly heavier than another.
Take two runners, give one a 15 kg weight in one hand, and give another 15 kg weights in both hands (30 kg total). I think the runner with weights in both hands would run faster than the one with one weight.
Thus, moving species evolve to be bilaterally symmetric.
If the organism has no need to move in certain direction, it doesn't really have bilateral symmetry, like trees or bushes (though big trees generally tend to have their center of mass close to their vertical axis).
While it's technically not a fungus, I had my first experience with Fuligo septica, or Dog Vomit mold. My wife were gardening in the late evening and went inside as it got dark. About an hour later I let the dogs out and this yellow mass was in the mulch, probably about 6x5" in size. We assumed it was vomit from a racoon or something, but figured it out when it grew back the next day (in two spots this time). I would remove it every morning, but it would grow back for the entire week in different spots in the mulch. It was fascinating, but incredibly gross and kind of creepy!
Note that the mushroom in question has been growing just below the surface for some time. The part we are used to thinking of as a mushroom is, on many species, something like an inflatable flower that is used to release their spores. It is built just below ground over a long time, then inflated at the right moment (rains), and then abandoned while the below-ground main body starts working up the energy to do it all again.
biggest hope for the survival of human race in the face of an alien onslaught is that we taste like yummy chicken. this way, they will keep us around for a long time
Consider that you're thinking too much of "cow farming" when you think of human farming.
No, humans are too useful to just eat! Even for menial tasks. You could think of slavery as a primitive form of human farming, but it's inefficient: being too harshly treated means poor health and mental performance, which means the tasks they can work in are limited. No, the farmers that would be worthy of farming humans would be more astute.
It's far more efficient to let a farmed kind live just comfortably enough to be healthy and develop themselves (free range), as long as they (1) are imposed with an element of scarcity that will force them to struggle to be useful in exchange for the scarce element and (2) the farmer is positioned in such a way that they extract value from these useful activities, with no downside.
As a bonus, because there's an element of competition for the scarcity, the farmed kind will police themselves (fairly or not), and band together, cooperating to generate an oversized portion of the scarce element at a certain level of increased risk for the leaders of the band - we can call them stakeholders. Winning stakeholders will be rewarded with increased amounts of the scarce element, and losers will be punished with a loss of scarce elements.
Extraordinarily successful stakeholders would be rewarded with benefits, and benefit not unlike the farmers - they are to be rewarded for their feats.
Those that are successful enough will be invited to travel to the farmers' homeland riding on a giant space phallus...
Some sci-fi concepts make for interesting jumping-off points when theorising about alien life. Perhaps there are aliens that have evolved or learned how to exploit physics as-yet unknown to us, giving them abilities akin to magic. Entities/shards from Worm come to mind.
How about purely informational beings with no physical body. Could they be considered 'alive?'. We can already simulate the nervous system of a nematode (http://openworm.org/), what if you scale that up to a fruit fly? Or an octopus? If it's 'thinking' in exactly the same way as a flesh-and-blood creature, is it conscious? Sapient? Sentient?
There's a lot of "we only have humans for our definition" or "we only have Earth life" but I think these comments miss a lot. Let's really break down what we would expect to see in intelligent and comparable (or even more advanced) life from extraterrestrials.
We know they have to use tools. You might point to crows, dolphins, or others and note that they use tools. But they don't in the same way that apes do. We're much better equipped to manipulate objects by using hands than using a mouth. Tentacles might be a better comparison but actually fingers allow for a lot of fine manipulation. Though I'm sure octopi could make tools that better work for them there's some mechanical reasons to believe hands are better. I mean there's the fractal nature of an arm helps with fine manipulation.
We know there's things like milk that help impart high nutrient content diets to young and there are correlations between lactate and fat to brain mass. We know this is a more efficient delivery system than say what birds to: eat, per-digest, and regurgitate. We actually expend a lot of energy to create milk.
These are just two (very incomplete and naive) examples, but what I'm trying to say is that not all options are equally likely. Maybe it won't be a hand. Maybe it'll be a tentacle with fractaling appendages (personally I wouldn't expect this because such a system is more complex) but I wouldn't expect something with (non-vestigial) wings, especially like a bat wing. Membranes can be easily punctured when working with objects and makes it hard to reach into confined spaces because of the necessity for large surface area to be able to fly.
So while yes, we only have Earth as a reference point we also have a lot of physics, biology, evolutionary pressures, game theory, and an understanding of tools and mechanics to lean on as well. I do think this does provide some restrictions to what is likely. _Not everything is on the table or equally likely._ I don't think it's naive to think that we have some good ideas of some basic characteristics that alien life would look like (we can apply similar ideas to non-highly intelligent life). I think it's naive to believe that anything is possible. These are claims that "sound smart" but are very naive and actually demonstrate a lack of basic knowledge.
So can we stop pretending like astrobiologists are idiots and haven't thought about this stuff? I don't know about you but I trust them more than I trust myself. They've spent significantly more time thinking about these things and have a far better background than us (except the handful of biologists and astrobiologists that are here).
The Cambrian Explosion shows that life can do all sorts of divergent things. The similarity of many current life forms (e.g. fish that are totally unrelated but work about the same) has more to do with environmental pressures producing similar results, that it has to do with what's possible?
I always wondered, what if there is "life" that exists going backwards in time? Like, consider our laws of physics, except entropy is decreasing. Imagine a "life form" which interacts with the world, grows, replicates, and evolves backwards in time. So to us, it would seem to start out as a massive colony, then shrink and devolve. To them, we would seem the same.
How would you even detect them? Communicate with them? You can't just send a message, because they would instantaneously "forget" it (since they process information backwards), and vice versa. I doubt we could consider them "alive" at all.
Also, their laws of physics would be so different. Imagine shards of glass, at rest on our world, suddenly start joining together into a glass bottle. That's what life looks like to them.
Yet everything else is the same. They live in the same, the same laws of physics. They could even exist on our planet. Except we exist in a state of increasing entropy, and they exist in a state of decreasing entropy.
An intelligent being in a 'state' of decreasing entropy seems a little difficult to imagine.
Much more realistic, IMO, would be a civilization that was made entirely of dark matter. Perhaps they might be able to infer our existence if we built some insanely powerful particle accelerator (and vice versa). If not then we would presumable only be able to communicate through gravitational effects...
The question isn't whether life could exist in a reversed universe, but whether this universe could exist in slices within ours like in the movie Tenet.
its possible but since we are in very very very early (think 10E9 out of 10E100) stages of our universe I'd imagine the reverse part would happen towards the end of our current time, assuming the time reversed processes have same endpoints as time fwd processes.
I think we have to consider the possibility (most likely), that the advanced versions of these lifeforms are much further along the evolutionary tree than we are. They might have evolved like us, but continued evolving and now look nothing like us.
I recall a Youtube video [can't find link right now] between Richard Dawkins and Neil deGrasse Tyson where they discuss probable expectations of alien biology based on parallel//independent evolution on Earth. Eyes were one example.
Prions are the simplest naturally occurring replicating structure I know of. Maybe there are resilient prions around, maybe they occur naturally in other very different environments... maybe there are alien prions.
We do not know if our evolutionary pressures are universal. We do not know if the evolutionary solutions developed here are appropriate even on other Earth-like planets, much less everywhere. Sensitive dependence on initial conditions could lead to radically different planetary environments, necessitating radically different mechanical solutions to survival, some (many, most?) of which we will never have even imagined.
What creatures would form under an intense magnetic field? In methane? In close orbit around a dim star? In a hot cloud nebula? Could we even recognize them as alive, much less intelligent? Definitely not if we're looking for bats and monkeys and octopuses
No, I think the whole genre of "life is much the same everywhere" suffers from a profound lack of imagination