Homo sapiens would indeed come from several populations across Africa

2023-06-09 09:55:28

If this conception of human origins in Africa goes against the most accepted theories even today, it is however not entirely new.

To help confirm this theory, Professor Simon Gravel of the Department of Human Genetics at McGill University and his colleagues tested the genetic material of present-day African populations and compared it to that of fossils of early populations ofA wise man found on the mainland.

They thus created a new model of human evolution, invalidating certain previous ideas.

The African continent seen from space.

Photo : Kilav

The different theories

According to one of these theories, a single central population lived on African territory some 150,000 years ago; the other populations would come from there.

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.says Simon Gravel, who recalls 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).

Genetics and math to the rescue

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 identify similarities and differences between the populations over the course of the last million years. This work has provided insight into genetic interrelationships and human evolution on the African continent.

This part of the work was done by American anthropologist and geneticist Brenna M. Henn of the University of California at Davis.

The groups in question were:

• Nama (Khoe-San of South Africa);
• Mende (from Sierra Leone);
• Gumuz (recent descendants of a hunter-gatherer group from Ethiopia);
• Amhara and Oromo (farming peoples of eastern Africa).

In addition, the research team used genetic material from Eurasian populations to trace colonial incursions and interbreeding in Africa.

The researchers then coupled the data from these different populations with mathematical models developed by Simon Gravel and his colleagues. The team thus used a new algorithm to quickly test the hundreds of possibilities and better understand the ancient structure of the 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 observe. »

— A quote from Simon Gravel, McGill University

The model that sticks 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 themadds the professor.

« Once in a while, maybe every 10,000 years, there were migrations between populations, and I speculate, events like climate change. »

— A quote from Simon Gravel, McGill University

Thus, there would have been enough exchanges between these populations for them to remain genetically consistent. They would thus have co-evolved.

Instead of seeing the modern human only appear in one place, one can imagine that different modern aspects may have appeared in different regions of the continent, in North Africa, East Africa and Africa from the South, for example. Then they would have spread to the mainlandsays Professor Gravel.

On leaving Africa

In these works, the researchers did not really attack the migrations ofA wise man outside the African continent. Professor Gravel says that future work could focus on the question, which is not without presenting difficulties.

« It’s a very complicated question. There have been several releases and many mixes. »

— A quote from Simon Gravel, McGill University

000 to 75000years, when they came out of Africa”,”text”:”In our model, we include a European population, but mainly to take the recent, postcolonial miscegenation, but not to try to solve what happened 50,000 to 75,000 years ago, when they left Africa”}}”>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 came out of the Africahe says.

The teacher would also like to use the new method to learn which mutations have helped shape our genetic makeup today from an adaptive perspective.

Simon Gravel would also like to refine this work carried out on the basis of five populations, since the more populations we have, the more complete the picture of today’s genetic diversity will be.

But there is still a lot of work to be done to get there. More populations, branches, migrations, it becomes very difficult to analyze! I still have a lot of work!