FREE YOUR MIND

DNA hints at African cousin to humans

Via: Science News

Expeditions to Africa may have brought back evidence of a hitherto unknown branch in the human family tree. But this time the evidence wasn’t unearthed by digging in the dirt. It was found in the DNA of hunter-gatherer people living in Cameroon and Tanzania.

Buried in the genetic blueprints of 15 people, researchers found the genetic signature of a sister species that branched off the human family tree at about the same time that Neandertals did. This lineage probably remained isolated from the one that produced modern humans for a long time, but its DNA jumped into the Homo sapiens gene pool through interbreeding with modern humans during the same era that other modern humans and Neandertals were mixing in the Middle East, researchers report in the August 3 Cell.

The evidence for ancient interbreeding is surprisingly convincing, says Richard “Ed” Green, a genome biologist at the University of California, Santa Cruz. “There is a signal that demands explanation, and archaic admixture seems to be the most reasonable one at this point,” he says.

Scientists have discovered that some people with ancestry outside Africa have DNA inherited from Neandertals or Denisovans, a mysterious group known only through DNA derived from a fossil finger bone found in a Siberian cave (SN: 6/5/10, p. 5; SN: 1/15/11, p.10).

But those researchers had DNA from fossils to guide their research. This time, researchers led by Sarah Tishkoff at the University of Pennsylvania in Philadelphia didn’t have fossil DNA, or even fossils.

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