A new ancient DNA find in a 400,000 year-old-bone discovered in Spain has thrown the theory of evolution into chaos, with leading scientists now admitting that they will have to “rethink the whole story.”
The study, published in the journal Nature this week (A mitochondrial genome sequence of a hominin from Sima de los Huesos, Nature 504, 16–17 (05 December 2013) doi:10.1038/504016a) focused on a femur bone from which ancient DNA had been retrieved and dated at 400,000 years ago.
Previously the oldest DNA yet extracted from remains was “only” 100,000 years.
When discovered, the bone was presumed by scientists to belong to some sort of Neanderthal forerunner, which would fit in with their theory of evolution.
However, the DNA, which was extracted by drilling into the bone and retrieving samples from its core, showed instead a similarity to another hominid type known as Denisovan.
The “Denisovans” are recently-identified Paleolithic-era members of a species of Homo or subspecies of Homo sapiens. Named after the remote Denisova Cave in the Altai Mountains in Siberia, Denisovan DNA extracted from a finger bone showed to be genetically distinct from the mtDNAs of Neanderthals and modern humans. Similar DNA has shown in up 6 percent of the DNA of Melanesians and Australian Aborigines.
That discovery fitted in with the currently popular “out of Africa” evolutionary theory which believed that the predecessors of present-day humans “evolved” from a common ancestor with Neanderthals and Denisovans who lived about half a million years ago in Africa.
These early types, the theory argued, then split off from humans’ lineage and left Africa, then split further into the Denisovans and Neanderthals about 300,000 years ago. The evidence suggested that Neanderthals headed west, toward Europe, and that the Denisovans moved east.
It was then claimed that human ancestors stayed in Africa, “evolving” into Homo sapiens about 200,000 years ago.
From there, it was argued, humans expanded from Africa into Asia and Europe about 60,000 years ago, where they interbred with Neanderthals and Denisovans.
This theory was predicated partly on the idea that Neanderthals “went west” and Denisovan “went east.”
The obvious complication created by the discovery of Denisovan DNA in the west now has the scientists baffled.
“Right now, we’ve basically generated a big question mark,” said Matthias Meyer, a geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and a co-author of the new study, was quoted as saying.
“Everybody had a hard time believing it at first,” Dr. Meyer said.
Dr. Meyer is hopeful that he and his colleagues will be able to get more DNA from the Spanish fossil, as well as other fossils from the site, to help solve the puzzle they have now stumbled across. “It’s extremely hard to make sense of,” Dr. Meyer said. “We still are a bit lost here.”