Genetic studies and new discoveries are now changing the way with thought of human evolution and human migration and in a growing number of cases that genetic evidence and new discoveries are turning out to be one surprise after another. Honestly though, I’m glad to see this happening because what genetic studies and these new finds are doing is expanding our vision and correcting some erroneous thinking that we’ve had for a long time.
Lately, we’ve begun to find that the popular Out of Africa theory may not be wholely correct with the discovery of a Neanderthal ancestor in Spain. We’ve now discovered that migrations were not solely out of Africa but there appear to have been many into Africa. Recently, we’ve also discovered that early man was in the Northern Yukon of Canada an amazing 300 kya which is later than anyone thought, to say the least.
We’ve also begun to uncover the mysterious Denisovans and come to find out that two genes (TBX15 & WARS2) are critical in how the body deals with fat in cold climates and heat. This study also is showing us that Inuit DNA matches very well with Denisovan DNA and that another possibility might be that what we are looking at is an archaic variant which evolved in Homo erectus somewhere in the high latitutdes of Asia about 1 mya.
Other studies are now indicating that the Americas were peopled 130 kya which is earlier than we thought also. But perhaps the most surprising find of late is the dating of Homo naledi in South Africa that shows it coexisted with early Homo sapiens and perhaps other human ancestral species.
As if this isn’t enough, now comes a genetic study suggesting that there is some proof on an “Out of America” origin for modern Homo sapien and if this is true then this study is going to turn human evolution and theory on its head!
In a paper published in 2009 is getting another look in light of all the new discoveries lately. It offers an interesting model that might explain diversity in Africans yet at the same time make them (Africans) the most RECENT humans rather than the oldest humans as we’ve thought. The traditional argument for the Homo sapien Out of Africa theory is the higher diversity in Africa versus non-African populations. Typically, the “proof” for this is in the form of a graph showing Heterozygosity decreases as one moves away from Africa. You can find these graphs just about everywhere on the Internet but here’s one example:
As you notice from this graph Heterozygosity falls from left to right and the published paper attempts to explain this by analyzing various alternative explanations but one they discard because it challenges the Out of Africa theory is the idea that there might be a non-African origin of humankind. Honestly, I think in this paper we have a clear example of discarding theories when the evidence fails to support our own pet theory and in this case that pet theory is the OOA theory.
What the authors found was that as populations moved away from Africa Heterozygosity increases. Essentially what they found was that if the original or first fully modern human group was in Africa then as we moved further away from Africa we should see more hterozygosity. But we don’t! So as Austin Whittall points out (see link below) “the model is wrong and despite having originated in Africa we did not go through this type of admixture.”
In this graph contained in the study the line shows heterozygosity increases as humans migrated out of Africa towards the Americas. This graph doesn’t make sense and suggests the model is wrong. It suggests people in the Americas have a higher heterozygosity in the Americas than people in Africa which is NOT the case. The opposite is the case in fact.
Whittall offers an alternative to explain this data which is a very interesting alternative. He suggests we “turn it around!” What that means is that if the original home of modern humans was in the Americas and not Africa then as our ancestors migrated outward from America and encountered various archaic populations they would have added diversity and eventually reached Africa mixing with the archaic species there as well. And if this were the case then heterozygosity would be the lowest in America and grow upward towards Africa. And this is EXACTLY what we find incidently. “When we turn the model around it coincides with the observed heterozygosity cline in modern humans,” says Whittall. The model and the data only make sense if you consider archaic modern humans evolved in the Americas and then spread into Asia, Europe, and Africa.
Whittall suggests this may be the case and turns the model around to look like the below graph:
When Whittall turns the graph around and changes the H. sapien migration to out of America into Africa heterozygosity increases. This graph makes sense because Africans do have a higher heterozygosity than people in the Americas.
In short, if the study is correct then people in Africa should have LOWER not higher heterozgosity (admixture). But they don’t. In fact they have higher heterozgosity. But, when Whittall turns the model around we find that people in Africa have higher heterozgosity while those in the Americas have lower heterozgosity which is exactly what the study found. In other words, people in the Americas have less admixture than people in Africa which supports an Out of America origins. To support an Out of Africa origins the data should show a lower admixture than people in the Americas but it doesn’t!
So is this possible? I mean is it possible that the Americas really are not the “New World” but the “Very Old World”? What do you think?
I’ll have more to say about this later as it is sort of confusing to me right now, honestly.