As another comment says, the author of this New York Times article, Carl Zimmer, is a very solid science writer who knows a lot about evolution. I have occasion to discuss human population genetics with psychologists who study behavior genetics, and when population genetics issues come up in those discussions, some of the new discoveries are surprising even to them. It's hard for reporters, us, and even the working researchers to keep up with the new findings in human population genetics. I'll share a finding here that surprised some researchers I discussed it with this week.
The first human genome to be sequenced was that of Craig Venter, who would be called a "white" man in the United States. The second human genome to be sequenced was that of James Watson, who is also regarded as "white" in either the United States or Britain. One of the first dozen or so human genomes to be sequenced was that of Korean scientist Seong-Jin Kim,[1] and his genome, even though "Asian," is more similar to Venter's than Venter's is to Watson's, and more similar to Watson's than Watson's is to Venter's.[2] Even though lineages are traceable in broad outlines by looking at human genes, there are quite a few human beings who resemble someone in someone else's group more than they resemble people in their own group. "The fact that, given enough genetic data, individuals can be correctly assigned to their populations of origin is compatible with the observation that most human genetic variation is found within populations, not between them. It is also compatible with our finding that, even when the most distinct populations are considered and hundreds of loci are used, individuals are frequently more similar to members of other populations than to members of their own population. Thus, caution should be used when using geographic or genetic ancestry to make inferences about individual phenotypes."[3]
So what's going in these studies of early hominid DNA is that we necessarily have tiny sample sizes, and we actually have no idea how much genetic variation there was in the population we call Neanderthal, how much in the population we call Denisovan, and so on. We will want to sequence as much ancient DNA as we can, and meanwhile sequence more modern human DNA from more people from more places around the world. But we won't be able to trace back the ancestry relationships unerringly, no matter what we do.
Ok, I have to ask this, and I apologize in advance for it being out of topic.
How on earth are you well informed on so many topics spanning different fields of science and literature? Your comments are amazingly well informed, and I would like to know how you do it.
[Blush] Thanks for your kind question. Let me first of all say that there is a lot that is discussed here on HN that I know nothing about, and in threads on those topics, I am in lurk mode, learning from the rest of you. So thanks.
On some topics, I have a different perspective just because I am older than most people here, so I remember history that other participants have to read about. Genetics research to be a responsible popular author about that research is part of my work, so this topic was work-related. I got lucky over the weekend, because I had just looked up the human population research articles to get ready for some contentious editing on Wikipedia, and thus all of the sources were at hand. Some of the other topics I comment about are also work-related, or related to my former work or my higher education degrees (neither of which were in computer science).
Dr. Peter Venkman: Ray, pretend for a moment that I don't know anything about metallurgy, engineering, or physics, and just tell me what the hell is going on.
Dr Ray Stantz: You never studied.
(I think the answer is simple: he has an interest in all those things, so he follows them).
He's probably also disciplined enough not to sound off on topics that he doesn't know anything about.
I was consulting (software) at a client site and one of the employees at the client remarked that I seemed to know everything about everything. I just replied that it was a trick - I only talk about the things I'm informed on, and when a question came up on a topic I didn't know anything about, I just redirected the conversation back to my expertise. I had a hammer and worked hard to make everything a nail. :)
So... when you're not a consultant with a need to impress people, you instead redirect the conversation to subjects other people know, which interests you? :-)
There was actually a pretty good article about the Denisova human in one of the recent National Geographics. One of the researchers mentioned in the article made a similar point, that for him the most likely indication of the Desnisova find is that we currently are separating into sub-species where there aren't any and that what we are finding are differences between individuals and not new sub-species.
I wonder when/if that will be the established view and some of these species will be consolidated.
If the raw number of DNA differences don't scale with genealogically and morphological 'similarity' - does that imply that the number of genes that get expressed in ways visible to us (facial shape, hair, etc) are really few in number?
Either that, or the analysis you described was plain incorrect, or we are looking at DNA 'wrong' - seeing patterns in noise and noise in patterns.
How is it that your interpretation of this evidence is so different to not only Zimmer's summary, but also all of the people quoted in the article? I think you would be more convincing if you addressed why these people interpreted the results so differently to you, than simply claiming that Zimmer has overlooked something.
OK, but you are still claiming that the correct interpretation of this evidence is very different to everyone in the article. Given that the facts you describe are very well known and basic, I doubt the people are unaware of them. They may, for example be using a measure of genetic difference that works better for distinguishing between groups.
The first human genome to be sequenced was that of Craig Venter, who would be called a "white" man in the United States. The second human genome to be sequenced was that of James Watson, who is also regarded as "white" in either the United States or Britain. One of the first dozen or so human genomes to be sequenced was that of Korean scientist Seong-Jin Kim,[1] and his genome, even though "Asian," is more similar to Venter's than Venter's is to Watson's, and more similar to Watson's than Watson's is to Venter's.[2] Even though lineages are traceable in broad outlines by looking at human genes, there are quite a few human beings who resemble someone in someone else's group more than they resemble people in their own group. "The fact that, given enough genetic data, individuals can be correctly assigned to their populations of origin is compatible with the observation that most human genetic variation is found within populations, not between them. It is also compatible with our finding that, even when the most distinct populations are considered and hundreds of loci are used, individuals are frequently more similar to members of other populations than to members of their own population. Thus, caution should be used when using geographic or genetic ancestry to make inferences about individual phenotypes."[3]
So what's going in these studies of early hominid DNA is that we necessarily have tiny sample sizes, and we actually have no idea how much genetic variation there was in the population we call Neanderthal, how much in the population we call Denisovan, and so on. We will want to sequence as much ancient DNA as we can, and meanwhile sequence more modern human DNA from more people from more places around the world. But we won't be able to trace back the ancestry relationships unerringly, no matter what we do.
[1] http://genome.cshlp.org/content/early/2009/05/26/gr.092197.1...
[2] http://www2.webmatic.it/workO/s/113/pr-1611-file_it-Barbujan...
[3] http://www.genetics.org/content/176/1/351.full