The human family tree just got another — mysterious — branch, an African “sister species” to the heavy-browed Neanderthals that once roamed Europe.
While no fossilized bones have been found from these enigmatic people, they did leave a calling card in present-day Africans: snippets of foreign DNA.
“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.
“We’re calling this a Neanderthal sibling species in Africa,” Akey said. He added that the interbreeding probably occurred 20,000 to 50,000 years ago, long after some modern humans had walked out of Africa to colonize Asia and Europe, and around the same time Neanderthals were waning in Europe.
History has not been kind to human groups who encountered this one and seemingly lethal group: anatomically modern humans.
In addition to finding evidence of the now-extinct humans, the team discovered a huge range of genetic diversity between the three groups. The human genome contains about 3 billion letters, or base pairs, of DNA. Before this study, scientists had found that about 40 million of these letters vary across human populations.
But in the 15 Africans, Tishkoff and Lachance found 3 million more genetic variants — a huge treasure trove of human diversity. Among this stunning variety, Tishkoff says they have pinpointed some of the genes responsible for the short stature of the pygmies, who average less than 5 feet in height. She also found that immune system genes and genes for taste and smell varied wildly between the three groups — confirming Africa as the seat of the widest range of human diversity.
It has not escaped the attention of human biologist and medical researchers that the genes of modern-day Africans are a treasure house of for all humanity. They possess our species' greatest reservoir of genetic diversity of which further study will shed new light on the heredity of the human body and mind.
You see where I'm going with this? If not, let's just leave it at that. I'm not going to spell it out for you.