Mystery Relative’s DNA Highlights Unique Human Traits
By Josh Fischman
August 30, 2012
The young woman from southern Siberia has been tantalizing scientists for about two years. They knew a few skimpy details, like that she was a she, and lived at least 50,000 years ago. Also she was not a modern human, but she or others in her group may have mated with our more direct ancestors, contributing a little DNA we still carry today.
Today we know what her DNA is — and more important, we have a better sense of what genes are uniquely ours. Many of them have to do with brain development and vision, and could be traits that set us apart from these near-modern humans in Siberia called Denisovans, their sister group the Neanderthals, and other shadowy relatives in Africa.
A newly unveiled and highly detailed genome map reveals those distinctions. It also uses genetics, not traditional geology, to place the woman in Denisova Cave about 80,000 years ago, not 50,000, and attempts to silence skeptics who have asserted that mating with modern humans was a product of geneticists’ imaginations. Not a bad haul from a piece of finger bone that’s smaller than your knuckle. “This represents a culmination of my efforts to study ancient DNA, which began in the 1980s when I started fooling around with mummies,” said Svante Paabo, a geneticist who led the work published on Thursday in Science. Mr. Paabo, from the Max Planck Institute of Evolutionary Anthropology, in Leipzig, Germany, published a “draft” genome sequence in 2010 — it indicated the gender of the finger-bone owner — but he acknowledges it was prone to error and covered only about 60 percent of the genome. The new sequence covers more than 99 percent, thanks to a new technique developed by Mr. Paabo’s team that, in essence, pulls apart the two mirror-image strands of the DNA double helix and exposes each one for a complete analysis, something hard to do when the fragmented, timeworn molecule is bound together.
Read the full article online in the Chronicle of Higher Education.