While it is generally established that modern humans originated in Africa, there are still some uncertainties about the evolution and movements of its first populations across the continent.
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The African savannah. (Illustration)
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Humans today would be the descendants of a few populations from different regions of Africa who would have mixed over time, show the work of a Canadian-American team of scientists.
If this conception of human origins in Africa goes against the most accepted theories still today, it is not entirely new.< /p>
To confirm this theory, Professor Simon Gravel of the Department of Human Genetics at McGill University and his colleagues tested the genetic material of current populations of Africa and compared it to that of fossils from early populations of Africa. #x27;Homo sapiens discovered on the continent.
They thus created a new model of human evolution, invalidating thereby certain previous ideas.
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The African continent seen from space.
According to one of these theories, a single central population lived on the African territory some 150,000 years ago; the other populations would come from it.
Another hypothesis is that this central population is the result of the interbreeding of modern humans and so-called archaic hominins, which contributed to human evolution.
What is interesting in our work is that it makes it possible to reconcile genetic models, archaeological and paleoanthropological models, since human remains and tools were found almost everywhere in Africa, affirms Simon Gravel, who recalls the the involvement of his former student Aaron Ragsdale, now at the University of Wisconsin–Madison, in this work published in the journal Nature (New window) (in English).
In an analysis comparing different anthropological models and genetic data, the team used contemporary genomic material from 290 individuals from four groups and geographically and genetically diverse Neanderthals to note similarities and differences between populations over the last million years. This work provided insight into genetic interrelationships and human evolution on the African continent.
This part of the work was carried out by American anthropologist and geneticist Brenna M. Henn of the University of California, Davis.
The groups in question were:
In addition, the research team used genetic material from Eurasian populations to trace the colonial incursions and crossbreeding in Africa.
The researchers then coupled the data from these different populations with mathematical models developed by Simon Gravel and his colleagues. The team used a new algorithm to quickly test hundreds of possibilities and better understand the ancient structure of populations.
What we did was to question the different scenarios proposed by anthropologists, but by translating them with mathematical models that make it possible to predict what we observe in genetic diversity. today. We then found the one that best fits the data we observed.
A quote from Simon Gravel, McGill University
The The model that fits best is one where there were several human populations similar to each other, but isolated for hundreds of thousands of years. These populations, although isolated, exchanged genes between them, adds the professor.
Once in a while, perhaps every 10,000 years, there were migrations between populations, and I speculate, events like changes climates.
A quote from Simon Gravel, McGill University
Thus, there would have been enough exchanges between these populations for #x27;they remain genetically coherent. They would thus have co-evolved.
Instead of seeing modern humans only appear in one place, we can imagine that different modern aspects could have appeared in different regions of the continent, in North Africa, in South Africa. x27;East and South Africa, for example. Then, they would have spread across the continent, specifies Professor Gravel.
In this work, the researchers did not really tackle the migrations of Homo sapiensoutside the African continent. Professor Gravel says that future work could focus on the question, which is not without its difficulties.
This is a very complicated question. There have been several releases and many mixes.
A quote from Simon Gravel, McGill University
In our model, we include a European population, but mainly to take recent, postcolonial interbreeding, but not to try to resolve what happened 50,000 to 75,000 years ago, when they were came out of Africa, he specifies.
The professor would also like to use the new method to learn which mutations have helped shape our genetic makeup today from an adaptation point of view.
Simon Gravel would also like to refine this work carried out using five populations, since the more populations we have, the more complete the portrait of today's genetic diversity will be.
But there is still a lot of work to do to get there. More populations, branches, migrations, it becomes very difficult to analyze! I still have a lot of work!
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