Study challenges what we know about the origin of human beings – 05/31/2023 – Science

Scientists are questioning the traditional theory about the origin of modern humans.

For years, the most accepted hypothesis was that the homo sapiens would have emerged from a single ancestral population in eastern or southern Africa.

In 2019, for example, a group of scientists claimed to have identified the exact place where the modern human being would come from, in an African region today basically located in Botswana, with some parts in Namibia and Zimbabwe.

But now, with powerful computer modeling and analysis of genetic data, scientists from Canada and the United States suggest that we are descendants of not just one, but several ancestral groups scattered across the African continent.

And specifically, at least two populations that lived simultaneously in Africa for a period of a million years before they mixed across the continent.

“We don’t know where they lived, but they were far enough apart that there were small genetic differences between the groups,” Brenna Henn, one of the study’s authors at the University of California, told BBC News Mundo, the BBC’s Spanish service. in Davis, USA.

scarcity of fossils

Our ancestors emerged in Africa at least 300,000 years ago, which is the date of the oldest fossil ever found that could belong to modern humans.

One of the challenges faced by research is that there are not many fossils of homo sapiens from the beginning of our evolutionary history.

And the geographic distribution of remains in places like Ethiopia and South Africa makes it harder to draw a conclusion about how our species arose and spread across the African continent before breaking out across the rest of the planet.

The new research indicates that several African ancestral groups contributed to the emergence of homo sapiensforming a kind of mosaic.

They migrated from one region to another and mixed with others, in a process that lasted hundreds of thousands of years.

In 2018, archaeologist Eleanor Scerri of the Max Planck Institute in Germany participated in a study to determine some of the basis for recent discoveries.

“We analyze archaeological, fossil, genetic and climate data and argue that human beings evolved from diverse populations in Africa. We call this model African multiregionalism or pan-African structured model”, explains Scerri.

“Currently, we state that genetic models should incorporate structured scenarios and we invite geneticists to do so”, continues the archaeologist. And that’s exactly what Henn and his colleagues are doing.

‘Twined Vine Branches’

“Our roots are in a very diverse general population, made up of fragmented local populations,” Scerri said in an article published in the journal Nature.

If we are going to represent it in a drawing, the scheme is likely to “look more like intertwined vine branches than a tree of life”.

The interweaving of these branches, with fragile separations caused by genetic differences, gave rise to an evolutionary concept that the researchers in the new study describe as “a loosely structured branch.”

To arrive at these conclusions, Henn and his colleagues employed a powerful computer model.

“The team used software developed by one of the authors, Simon Gravel, from McGill University in Montreal, Canada, which was able to coordinate the extensive computing power needed for the extended model”, according to the journal Nature.

The scientists incorporated genome sequencing data from 290 people currently living in East and West Africa and members of the Nama people, who live in southern Africa.

Then they created different scenarios of populations existing in Africa during different time periods and looked at which ones might produce the DNA diversity found in people alive today.

“This diffusion of genomic data has helped researchers understand and track the historical movement of genes across generations,” explains Nature.

In this way, the study concluded that all of us who live today can trace our ancestors to at least two distinct populations that lived in Africa a million years ago.

“All humans share a relatively common ancestor, but the history of our more distant past is more complicated than a species that evolved in a single location or in isolation,” says geneticist Aaron Ragsdale of the University of Wisconsin-Madison, in the United States, leader of this study.

Genome data from 91 European citizens were also examined to represent the influence of the postcolonial era and Neanderthals, the extinct human species that was concentrated in Europe until about 40,000 years ago.

Bases for the future

Scerri concludes that this study is important because, in addition to creating a “new model of human evolution”, it confirms the theory of multiple origins from a genetic point of view.

“It complements other genetic studies that use DNA from African populations that lived between the last 10,000 to 30,000 years and already see evidence of deep structure for our species,” she said.

“It’s exciting that these results confirm our model and drive yet another nail in the coffin for the idea that humans evolved from a single population, in a single region of Africa,” adds Scerri.

Whether or not the conclusions of this recent study are confirmed, there is no longer any doubt that the complexity of the origin of our species will continue to be the subject of countless studies.

And new studies will increasingly rely on rapid advances in technology.