Oldest Human Genome Reveals When Our Ancestors Mixed With Neanderthals

sciencehabit writes DNA recovered from a femur bone in Siberia belongs to a man who lived 45,000 years ago, according to a new study. His DNA was so well preserved that scientists were able to sequence his entire genome, making his the oldest complete modern human genome on record. Like present-day Europeans and Asians, the man has about 2% Neanderthal DNA. But his Neanderthal genes are clumped together in long strings, as opposed to chopped up into fragments, indicating that he lived not long after the two groups swapped genetic material. The man likely lived 7000 to 13,000 years after modern humans and Neanderthals mated, dating the mixing to 52,000 to 58,000 years ago, the researchers conclude. That's a much smaller window than the previous best estimate of 37,000 to 86,000 years ago.

Comments

Yeah but ...

[ve3oat]

The same tests on DNA from another man from the same era and locale but from a different Y-haplogroup (and different mt-haplogroup) might show a completely different proportion of genetic mixing and time to most recent mating. Don't draw too many conclusions from a sample of just one.

Re:Yeah but ...

[Doubting Sapien]

Mod parent up. The article as written is dumbed down and misleading in many ways. Against my usual temperament I'm going to make a sociological/anthropological argument that someone reading the article will draw very wrong conclusions about the nature of prehistoric Neanderthal-modern human interaction. Genetic inheritance or progeny happens to be the only evidence we have right now about early Neanderthal-modern human interaction. But it does not say anything useful about when we "first had sex with" them as the article claims. Consider the following: Archaeological evidence suggests that large scale violence we would consider warfare was a part of human life as far as 7,500 or possibly 14,000 years ago. Does that mean ancient society was all about peace and love before that time? No. There is too little information to make such sweeping conclusions. To return to the subject at hand, not all sexual encounters with Neanderthals are going to leave evidence for us to conveniently find. What we *DO* know at this point is that at least one such encounter resulted in a pregnancy that was carried to term and the resulting offspring lived long enough to have children of his/her own who continued to survive. That's ALL we know. Put another way, imagine the young men and women of ancient communities playing a game of "fuck, marry, or kill" that included their funny looking neighbors. The visual may not be pleasant, but any earlier incidents of war-rape and deliberate infanticide due to parental rejection will leave little to no evidence behind for us. And barring extreme luck, there is almost NO WAY we can know if/when such incidents occurred. Who really knows when Neanderthals and us *FIRST* had sex?

Title seems a bit racist

[Parafilmus]

The author's cro-mag bias is showing.

Her title implies that the neandertals in question are not also our ancestors.

A better title might have been "...genome reveals when our Cro-Magnon ancestors had sex with our Neandertal ancestors."

Question for sequencing expert.

[tloh]

How accurate is it for the media to say a "complete" genome was sequenced? I know a little molecular biology and have been lead to believe that certain types of DNA, (centromeres, telomeres, other such regions with lots of repetitive sequences or "fragile sites") are very hard to sequence reliably. Are these "swept under the rug" in a "complete" sequence? Perhaps a related question, how are non-coding regulatory portions of chromosomes handled in whole genome analysis?

Re: Exinction

[jc42]

My guess is that the fact that no organisms exist with a Neanderthal genome defines them as extinct. Where one draws the line is more art than science I guess ... I know that there are some genetics in us (like the HMG group of proteins) that are ancient, but work so well that we still retain them. That doesn't mean the first species to have evolved them isn't extinct, it just means we evolved from them.

Well, I don't think that quite matches the scientific concept of "species". By your definition, almost all species who were alive 50,000 years ago would be considered extinct, but hardly any biologists would agree with that. It's true that no humans alive today have 100% Neanderthal genes, but it's also nearly certain that there are no living humans with 100% Cro-Magnon genes, either. What happened would be considered a mixing of several human sub-species after migrations of one or more African groups into Eurasia. The Cro-Magnon sub-species disappeared, too, and modern human Caucasian and Asian sub-species are the results of that mixing. This sort of thing happens in species all the time, when conditions allow such genetic mixing, and the result is rarely considered a new species.

The fact is that modern humans are all one species. We can and do interbreed when groups mingle, and there are no groups of modern humans that are genetically incompatible. If sub-species "disappear" by genetic mixing, that is usually not called an extinction event. It's just the routine and normal mingling of subspecies.

An interesting contrast is that most North American duck species are known to hybridize occasionally, and the offspring are usually fertile. Does this mean they're really all one species? No, because they all mingle a lot, but interbreeding is rare. They have "behavioral" species-separation features, mostly based on female mate choice. The females are mostly all mottled brown (protective coloring), and the males often approach females of other species (because they can't tell them apart either ;-). But the females usually only accept males that have the "right" color markings; the others are ugly to them. This suffices to keep the species separate, though there is probably a very low level of genetic interchange between many of the species.

But humans aren't like this. Even if we do generally prefer mates in our own subspecies, most of us do find many members of other subspecies physically attractive, and we'll mate with them given the opportunity. This means that we really are all the same species. We now have good evidence that the Neandertals were merely another subspecies, because when they had the opportunity, they did interbreed with those slender, dark-skinned folks who migrated into their territory. They did so often enough to produce a new subspecies that's physically distinct from either of the earlier two (or three or more).