WASHINGTON, May 18 (Reuters) – Our species appeared in Africa more than 300,000 years ago, with the oldest known Homo sapiens fossils discovered at a site in Morocco called Jebel Irhoud, located between Marrakech and Atlantic coast.
But the lack of Homo sapiens fossils from early in our evolutionary history and the geographical spread of African remains in places like Ethiopia and South Africa make it difficult to piece together how the species arose and spread. our species across continents before trekking across the globe. A new study using genome data from modern African populations offers insight into how this might have unfolded.
Research indicates that many ancestral groups from across Africa contributed to the emergence of Homo sapiens in a patchwork fashion, moving from one region to another and mixing with each other over hundreds of thousands of years. year. It has also been found that everyone alive today can trace their ancestry to at least two distinct populations that have been present in Africa since about a million years ago.
The findings do not support a long-held hypothesis that a single region in Africa gave rise to Homo sapiens or a scenario involving admixture with an unknown closely related species in the human evolutionary lineage within Africa.
“All humans share a recent common ancestor, but the story in the deeper past is more complex than our species evolving in a single location or in isolation,” said the University of Wisconsin population geneticist. -Madison’s Aaron Ragsdale, lead author of the published study. this week in the journal Nature.
Ancestral groups tend to be spread over a geographic landscape in a population structure that, says Ragsdale, “is ‘fragile,’ meaning there is constant or at least intermittent movement between groups, and it maintains genetic similarity with ancestral populations.”
Lacking fossil remains and archaeological evidence, researchers have turned to genome data from living people to find clues about the past. They analyzed genome data from 290 people, mostly from four geographically and genetically diverse African peoples, to track similarities and differences between populations and identify genetic connections among hundreds of thousand years.
These include: 85 individuals from a West African group called the Mende from Sierra Leone; 44 individuals from the Nama Khoe-San group from southern Africa; 46 individuals from the Amhara and Oromo groups in Ethiopia; and 23 individuals from the Gumuz group, also from Ethiopia. Genome data from 91 Europeans were also analyzed to account for the influence of the post-colonial period and from a Neanderthal, the extinct human species that was concentrated in Europe until about 40,000 years ago.
The fossil record is sparse for the period that would be most informative about the emergence and spread of Homo sapiens, and there is no ancient DNA from skeletal or dental remains from these periods, the researchers said.
“While we find evidence of anatomically modern human remains and artifacts in various parts of Africa, they are so scattered in space and time that it is difficult to understand their relationships to each other, and us,” said study geneticist and study co-author Simon Gravel of McGill University in Montreal. “Are they related to each other? Are they related to our ancestors, or are they local populations that have disappeared?”
“Genetic data is inherited from a continuous chain of transmissions dating back to before the origins of modern humans. Correspondence with contemporary humans contains a wealth of information about this chain of events,” added Gravel. “By building models of how these transmissions occurred, we can test detailed models relating past populations to current populations.”
Reporting by Will Dunham, Editing by Rosalba O’Brien
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