Despite the attempt at humor in my title, this is really a fascinating development. Scientists comparing the genome of Neanderthals with that of modern humans have discovered that the former species lives on, apparently, in most of us. Yes, this seems to indicate some interbreeding between Neanderthals and our own species.
Fascinating, isn't it? According to this article on the BBC News website, and to this one in the Guardian (London), modern humans outside of Africa contain between 1% and 4% of genes which came originally from Neanderthals. Previous thinking had been that Neanderthals had not contributed to our own gene pool, that they'd lived alongside modern humans for tens of thousands of years, but without mixing sexually. It's good to know that Neanderthals have left at least a little of themselves behind, don't you think?
If you're interested in the details, here is a good blog post describing the history of our thinking about Neanderthals, from the initial discovery of a partial skull in 1856 (remains found earlier weren't recognized as being from an extinct human species). It shows you how science works, constantly asking questions and painstakingly discovering new details which get us closer to the complete truth. As you know - or certainly should - science isn't any particular dogma, but rather a process. Science welcomes questions, but you must have evidence to back up any assertions.
In this case, briefly, you must understand that Africans are much more diverse genetically than the rest of us. That's because we evolved in Africa, and only a small portion of humanity (containing only some of our genetic diversity) left the continent. They spread across the planet, but each migration involved only a part of the local population. That's why Native Americans, for example, at the end of a very long migration route - or, rather, a series of migrations, each involving only a part of the local population - are relatively poor in genetic diversity.
Africans have the greatest genetic diversity, because they are the descendants of the majority who stayed put. But for the most part (modern travel is starting to change this), they don't have this small proportion of Neanderthal genes, which were apparently acquired soon after my own ancestors left the continent (we conclude this because the rest of the world shares them). That's how we can tell that they interbred.
After all, Neanderthals and we homo sapiens share 99.7% of our DNA, since we had a common ancestor 400,000 years ago. Obviously, it's not that it's unusual to find the same genes in both species. But when Africans don't have these genes, it's good evidence that they appeared in Neanderthals after that species split from our own and appear in other populations of modern humans only because of interbreeding.
Apparently, these aren't particularly important genes. Diversity in general is valuable, and I don't think we know exactly what all of these genes do, but they don't seem to be especially favored by evolution. Also, this isn't guaranteed proof that Neanderthals and modern humans interbred. In science, after all, everything is tentative, always subject to being overthrown by newer evidence. There is never any proof, only evidence. And there are other explanations that could account for this, though they seem much less likely.
The neat thing is that these were people, just like us. Very similar to us, in fact. They were stockier and stronger than the long-limbed modern humans who emerged from Africa afterward, but they had brains about the size of our own. They made tools and even jewelry. Their disappearance was a tragedy, just as our own extinction would be. So it's wonderful to think that they might live on, at least to a small extent, in us.
No comments:
Post a Comment