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).
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).