Africans have more Neanderthal ancestry than previously thought - though still less than most people outside of Africa. Neanderthals were our closest evolutionary relatives, inhabiting parts of Europe and Asia from possibly more than 800,000 years ago until around 40,000 years ago.
     People who migrated out of Africa around 60,000 to 80,000 years ago interbred with Neanderthals, and some human groups carrying Neanderthal genes returned to Africa. Neanderthal gene variants inherited by modern Africans include those involved in bolstering the immune system and modifying sensitivity to ultraviolet radiation. On average Neanderthal DNA accounts for about 0.5 percent of individual Africans' genetic inheritance - far more than reported in earlier studies. Most present-day people outside Africa carry about three times that amount. More than 94 percent of Neanderthal DNA sequences detected in today's Africans have also been observed in non-Africans.
     Other DNA evidence suggests that Homo sapiens and Neanderthals interbred in Europe and Asia at least 50,000 years ago, but Neanderthals didn't mate with ancient people in Africa. Low levels of human migration from Europe to Africa over roughly the past 20,000 years introduced Neanderthal DNA into African populations.
     The new study also found comparable proportions of Neanderthal DNA in modern Europeans and East Asians - about 1.7 percent and 1.8 percent respectively. Earlier studies estimated East Asians would have substantially more Neanderthal ancestry than Europeans. Africans share 7.2 percent of their Neanderthal ancestry with Europeans, 2 percent with East Asians. That makes Europe a more likely source of back-to-Africa migrations by humans carrying Neanderthal genes.
     The report best fits a scenario in which human evolution after around 300,000 years ago featured hybridization between genetically different Homo populations and back-to-Africa migrations.
     Researchers also detected a human migration out of Africa roughly 100,000 to 150,000 years ago that introduced human genes into Neanderthals. Some African DNA that appeared to have been inherited from Neanderthals actually came from those ancient humans.

Edited from ScienceNews (30 January 2020)