Are Africans interested in Eurasian history?

Africans inherited genes from someone they did not know

Early quackery: The ancestors of today's Africans must have mated with a hitherto unknown other human species. Researchers have now discovered traces of this extinct archaic population in the genome of population groups from sub-Saharan Africa. According to them, this surprising finding also affects our understanding of the genetic heritage of us Europeans.

When our ancestors left Africa, a story of infidelities began: Genome analyzes show that anatomically modern humans crossed several times with Neanderthals and Denisovans. Archaic Neanderthal DNA can be found in the genome of Europeans to this day. In Asia, on the other hand, some population groups carry Denisova genes - and recently researchers have even discovered traces of a third human species in the genome of individuals from Asia and Oceania.

So far, however, it was unclear whether such affairs between Homo sapiens and other human species also occurred in Africa. Only in populations from North Africa have traces of Neanderthal and Denisova genes been found. Africans from other parts of the continent, on the other hand, were viewed by experts as a model for a population without so-called introgression. But was there really never a gene transfer from a foreign species to Homo sapiens?

Artificial intelligence as a helper

To check this, scientists led by Belen Lorente-Galdos from the Pompeu Fabra University in Barcelona have now examined the genetic make-up of today's Africans. In total, they analyzed the genome of 21 individuals for their study, who represented 15 different populations from all parts of the continent and covered all important language groups and lifestyles.

The team had the genetic data of these people analyzed by an artificial intelligence (AI). This algorithm had learned to use the gene sequences to infer demographic history. Which crossing events from the past could best explain the current composition of the genetic make-up of the populations examined?

Traces of an unknown

The surprising result: "In order to be able to explain the genetic diversity in the African population groups, the presence of another extinct archaic population, with which anatomically modern people in Africa crossed," reports co-author Oscar Lao from the Barcelona Institute for Science and Technology .

Specifically, the researchers found traces of such a smack in populations from sub-Saharan Africa, including the Khoisan, the Mbuti pygmies and the Mandinka people. But who was the stranger who mated with the ancestors of these Africans and who has been immortalized in their genome to this day? According to the team's investigations, these must be representatives of a previously unknown, extinct human line.

"Archaic Ghost Population"

“In fact, during the Pleistocene in sub-Saharan Africa, the ancestors of anatomically modern humans coexisted with other archaic humans,” emphasize the scientists. According to them, the now identified “archaic ghost population” split off from the lineage of Homo sapiens at around the same time as the Neanderthal and Denisova lineages separated from it.

This result now also has an impact on the understanding of the genetic heritage of population groups outside Africa, as the research team emphasizes. Further analyzes showed: If one takes into account the presence of the newly identified ghost population in corresponding models, instead of assessing the African genome as unaffected by foreign factors, the picture of the genome composition of Eurasian populations also changes.

Three times more Neanderthal genes?

"Our results reveal that the estimated proportion of the Neanderthal genome in Eurasians is strongly influenced by the presence of the ghost population," the scientists write. “The amount of DNA that comes from Neanderthals could therefore be up to three times higher than previous models suggest,” concludes Lorente-Galdos. (Genome Biology, 2019; doi: 10.1186 / s13059-019-1684-5)

Source: Center for Genomic Regulation

April 29, 2019

- Daniela Albat