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Africans today possess more Neandertal ancestry than previously thought, a new analysis shows, though still not as much as most people outside of Africa.

People who migrated out of Africa around 60,000 to 80,000years ago interbred with Neandertals. That set the stage for some human groupsto return toAfrica carrying Neandertal genes that spread throughout the continent, apparentlybecause those genes proved beneficial to ancient Africans, researchers reportJanuary 30 in Cell.

Sets of Neandertal gene variants inherited by modern Africans include genes involved in bolstering the immune system and modifying sensitivity to ultraviolet radiation, geneticist Joshua Akey of Princeton University and his colleagues found. Those genes presumably spread quickly once introduced to African humans. A new statistical approach for detecting ancient genetic material thats still present in modern DNA, developed by Akeys team, enabled this discovery of genetic inheritance that has gone unnoticed until now.

The researchers new technique also detected a human journeyout of Africa roughly 100,000 to 150,000 years ago that led to the introductionof human genes into Neandertals via interbreeding. Some African DNA that appearedat first to have been inherited from Neandertals actually came from thoseancient humans when scrutinized more closely, the investigators say.

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Our work highlights how humans and Neandertals interactedfor hundreds of thousands of years, with populations dispersing out of and backinto Africa, Akey says. Remnants of Neandertal DNA survive in every modernhuman population studied to date.

Akeys team analyzed DNA from 2,504 present-day Africans,Europeans and East Asians. Each persons DNA was compared with DNA extracted byother researchers from Neandertal fossils found in Siberia and in southeasternEurope.

The new statistical program calculates the probability thatspecific segments of a persons DNA represent an inheritance of Neandertal DNAsegments. In contrast, previous approaches compared living peoples DNA to thatof Neandertals as well as to a modern African group assumed to lack Neandertalancestry, often Nigerias Yoruba people. But if those reference groups actuallypossess Neandertal DNA, as indicated by the new report, then earlier studiesunderestimated Neandertals genetic legacy.

Neandertals were humans closest evolutionary relatives,inhabiting parts of Europe and Asia from possibly morethan 800,000 years ago until around 40,000 years ago (SN: 5/15/19). Neandertal DNA accounts for, on average, about 0.5percent of individual Africans genetic inheritance, or genome, far more thanreported in earlier studies, Akeys team concludes. Most present-day peopleoutside Africa carry about three times as much Neandertal DNA as Africans do, theresearchers say. More than 94 percent of Neandertal DNA sequences detected intodays Africans have also been observed in non-Africans, they say.

Surprisingly, the new study also identifies comparable proportionsof Neandertal DNA in the genomes of modern Europeans and East Asians, about 1.7percent and 1.8 percent, respectively. Earlier studies had estimated that EastAsians possessed about 20 percent more Neandertal ancestry than Europeans.

Although the efficacy of Akeys statistical method awaitsindependent confirmation, it seems real to me, says paleogeneticist CarlesLalueza-Fox of the Institute of Evolutionary Biology in Barcelona. Along with a2012 study of Neandertal ancestry in modern North Africans, the new report bestfits a scenario in which human evolution after around 300,000 years agofeatured failed, partly successful and successful population movements out ofAfrica, hybridizationbetween genetically different Homopopulations and back-to-Africa migrations (SN: 10/5/16).

Akeys statistical approach provides an unprecedentedopportunity to detect Neandertal ancestry in people around the world, sayspaleogeneticist Cosimo Posth of the Max Planck Institute for the Science ofHuman History in Jena, Germany.

Other DNA evidence suggests that Homo sapiens and Neandertals interbredin Europe and Asia at least 50,000 years ago (SN: 9/21/16). But Neandertals didnt mate with ancient people inAfrica, Akeys group finds. Instead, the teams computer simulations indicatethat low levels of human migration from Europe to Africa over roughly the past 20,000years injected Neandertal DNA into African populations.

That conclusion stems from a geographic imbalance in sharedNeandertal DNA among people today. Africans exclusively share 7.2 percent oftheir Neandertal ancestry with Europeans, versus 2 percent with East Asians,the researchers find. That makes Europe a more likely launching ground forback-to-Africa migrations by humans carrying Neandertal genes.

The new findings call for the reevaluation of fossils andarchaeological discoveries both in and out of Africa, as well as more intense searchesfor ancient genes in modern Africans, says geneticist Sarah Tishkoff of theUniversity of Pennsylvania.

Read more:
A new genetic analysis reveals that modern Africans have some Neandertal DNA too - Science News

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