Svanta Paabo is a Swedish evolutionary biologist specialising in evolutionary genetics who says, “…from a genomic perspective we are all Africans”. His second statement is even more revealing, “…there is no one absolute difference between the people inside Africa and those outside, not in any of the sequences…when we look at people and see a person from Africa and a person from Europe or Asia, we cannot, for a single position in the genome with 100 per cent accuracy, predict what the person would carry…we can, of course, look at these people and quite easily say where they or their ancestors came from…we so readily see — facial features, skin colour, hair structure — but they are not determined by single genes with big effects, but are determined by many different genetic variants that seem to vary in frequency between different parts of the world.”
Paabo says, “Each of us, of course, contains two human genomes — one from our mother’s and one from our father’s. And they are around three billion letters long. And we will find that the two genomes in me, or one genome of mine we want to use, will have about three million differences in their order. And what you can then also begin to do is to say, ‘How are these genetic differences distributed across the world?’ And if you do that, you find a certain amount of genetic variation in Africa. And if you look outside Africa, you actually find less genetic variation. This is surprising, of course, because in the order of six to eight times fewer people live in Africa than outside Africa. Yet the people inside Africa have more genetic variation. Moreover, almost all these genetic variants we see outside Africa have closely related DNA sequences that you find inside Africa. But if you look in Africa, there is a component of the genetic variation that has no close relatives outside. So a model to explain this is that a part of the African variation, but not all of it, has gone out and colonised the rest of the world. And together with the methods to date these genetic differences, this has led to the insight that modern humans — humans that are essentially indistinguishable from you and me — evolved in Africa, quite recently…” He says this happened between 200,000 and 100,000 years ago, and that later, between 100,000 and 50,000 years ago, these human beings “went out of Africa to colonise the rest of the world.”
Paabo goes on to tell us that there are innumerable variations in each individual sequence of the genome. But what is more interesting, he says, is that there is no absolute difference between the genome sequences of different races. Echoing the idea, poetic idea, that no men are foreign, no men strange, Paabo says something even more fascinating, “…those traits that we so easily observe in each other…they’re really on the surface of our bodies. They are what we just said — facial features, hair structure, skin colour... But if we look on other parts of our bodies where we don’t directly interact with the environment — our kidneys, our livers, our hearts — there is no way to say, by just looking at these organs, where in the world they would come from.”
Paabo reveals that in addition to the humans in Africa, there were the Neanderthals. The genome sequence of the Neanderthals is more similar to every other race outside of Africa, Europeans or even the Chinese. “So the model we’ve proposed to explain this is that when modern humans came out of Africa some time after 100,000 years ago, they met Neanderthals. Presumably, they did so first in the Middle East, where there were Neanderthals living. If they then mixed with each other there, then those modern humans that became the ancestors of everyone outside Africa carried with them this Neanderthal component in their genome to the rest of the world. So that today, the people living outside Africa have about two and a half percent of their DNA from Neanderthals.”
Web link: http://www.ted.com/talks/svante_paeaebo_dna_clues_to_our_inner_neanderthal/
