It's become a pretty well-researched fact that ancient homo-sapiens mated with Neanderthals. Scientists now think that this genetic union has made people of East Asian and Eurasian descent more susceptible to medical conditions like rheumatoid arthritis and LDL cholesterol buildup. But a new study by genomicists at Vanderbilt University in Nashville has unearthed some new discoveries about our ancestors' intimate time with the Neanderthals. Interbreeding with Neanderthals actually replenished some of the African genes that modern humans lost when they left the motherland.
"They left many beneficial variants behind in Africa," evolutionary genomicist, Tony Capra, told Science Mag."Interbreeding with Neanderthals provided an opportunity to get back some of those variants, albeit with many potentially weakly deleterious Neandertal alleles as well."
These Neanderthal genes were a part of the basic ancestral human condition which homo-sapiens lost when they migrated out of Africa. The migration caused a "genetic bottleneck" of sorts, as smaller groups of ancient humans exited the continent. The genetic diversity you'd find in a larger African population all but disappeared.
Researchers found the ancient African genes when they examined the DNA of the over 20,000 people who are a part of the 1000 Genomes Project and Vanderbilt's BioVU database of electronic health records. During their examination, they found chains of Neanderthal chromosomes which shared mutations with genes found in all of the African people they studied. These genes were from the Yoruba, Mende and Esan peoples.