Researchers led by geneticist Sarah Tishkoff from the University of Pennsylvania have sequenced the genomes from three different African ethnic groups. Among other things, they found that humans apparently acquired some genetic sequences from other ancient cousin branches of the human family. As the Washington Post reported:
“Geneticists like euphemisms, but we’re talking about sex,” said Joshua Akey of the University of Washington in Seattle, whose lab identified the mystery DNA in three groups of modern Africans.
Specifically, novel sequences found in the genomes of modern Africans are apparently DNA from a hominin species that diverged from our species' direct line 1.2 million years ago. However, their paleo-great grandchildren evidently enjoyed each other's company sometime around 50,000 years ago. From the Post:
The find offers more evidence that for thousands of years, modern-looking humans shared the Earth with evolutionary cousins that later died out. And whenever the groups met, whether in Africa or Europe, they did what came naturally — they bred. In fact, hominid hanky-panky seems to have occurred wherever humans met others who looked kind of like them — a controversial idea until recently.
In 2010, researchers from the Max Planck Institute for Evolutionary Anthropology in Germany announced finding Neanderthal DNA in the genomes of modern Europeans.
Barrel-chested people whose thick double brows, broad noses and flat faces set them apart from modern humans, Neanderthals disappeared about 25,000 or 30,000 years ago.
Another mysterious group of extinct people recently identified from a 30,000-year-old finger bone in Siberia — known as the Denisovans — also left some of their DNA in modern-day Pacific Islanders.
And while modern humans and the newly found “archaic” Africans might be classified as distinct species, they produced viable offspring.
A study published in PLoS Genetics on July 19 makes estimates of the admixture of genes derived from interbreeding:
Overall, these genomic analyses of admixture suggest that 1%–3% of the genome of all Eurasians and native Amerindians is of Neanderthal origin, and that Papua New Guineans and Australians have another 3.5% of their genome of Denisovan origin.
The newly identified archaic sequences make up about 2.5 percent of the genomes of modern Africans.
Disclosure: My buddy Princeton University biologist Lee Silver has combed through my genotype screening information and could not find any Neanderthal DNA. However, my critics assure me that it's there.