DNA data tender proof of unknown dead human relative


VANCOUVER — Traces of long-lost human cousins may be hiding in current people’s DNA, a new computer analysis suggests.

People from Melanesia, a area in the South soothing encompassing Papua New Guinea and surrounding islands, may carry inherited evidence of a previously unknown dead hominid species, Ryan Bohlender reported October 22 at the annual meeting of the American Society of person Genetics. That species is probably not Neandertal or Denisovan, but a different, connected hominid group, said Bohlender, a statistical geneticist at the University of Texas MD Anderson Cancer Center in Houston. “We’re missing a populace or we’re misunderstanding something about the relationships,” he said.

This strange relative was almost certainly from a third branch of the hominid family tree that produced Neandertals and Denisovans, an extinct distant cousin of Neandertals. While many Neandertal fossils have been found in Europe and Asia, Denisovans are known only from DNA from a finger bone and a couple of teeth found in a Siberian cave in (SN: 12/12/15, p. 14).

Bohlender isn’t the first to propose that leftovers of old human relatives may have been potted in human DNA even though no fossil leftovers have been found. In 2012, another group of researchers suggested that some people in Africa carry DNA heirlooms from an extinct hominid species (SN: 9/8/12, p. 9).

Less than a decade ago, scientists open that human ancestors mixed with Neandertals. People outside of Africa still carry a small amount of Neandertal DNA, some of which may cause health problems (SN: 3/5/16, p. 18). Bohlender and colleagues calculate that Europeans and Chinese people carry a similar amount of Neandertal ancestry: about 2.8 % Europeans have no hint of Denisovan descent, and people in China have a tiny amount — 0.1 % according to Bohlender’s calculations. But 2.74 percent of the DNA in people in Papua New Guinea comes from Neandertals, and another 3 to 6 percent stems from Denisovans, Bohlender calculated.

When trying to explain that strangely high percentage of extinct lineage, Bohlender and colleagues came to the end that a third group of hominids may have bred with the intimates of Melanesians. “Human history is a lot more complex than we thought it was,” Bohlender said.

Another group of researchers, led by Eske Willerslev, an evolutionary geneticist at the Natural History Museum of Denmark in Copenhagen, newly came to a similar conclusion. Willerslev’s group examined DNA from 83 aboriginal Australians and 25 people from native populations in the Papua New Guinea highlands (SN: 10/15/16, p. 6). The researchers found Denisovan-like DNA in the study volunteers, the group reported October 13 in Nature. But the DNA is hereditarily distinct from Denisovans and may be from another dead hominid. “Who this group is we don’t know,” Willerslev says. They could be Homo erectus or the extinct hominids found in Indonesia known as Hobbits (SN: 4/30/16, p. 7), he speculates.

But researchers don’t know how hereditarily varied Denisovans were, says Mattias Jakobsson, an evolutionary geneticist at Uppsala University in Sweden. A different branch of Denisovans could be the group that mated with intimates of Australians and Papuans.

Researchers know so little about the hereditary makeup of extinct groups that it’s hard to say whether the extinct hominid DNA actually came from an undiscovered species, said statistical geneticist Elizabeth Blue of the University of Washington in Seattle. DNA has been examine from few Neandertal fossils, and Denisovan remains have been found only in that single cavern in Siberia. Denisovans may have been extensive and genetically diverse. If that were the case, said Blue, the Papuan’s DNA could have come from a Denisovan population that had been separated from the Siberian Denisovans for long enough that they looked like distinct groups, much as Europeans and Asians today are hereditarily different from each other. But if Denisovans were not genetically diverse, the strange extinct ancestor could well be another species, she said.

Jakobsson says he wouldn’t be surprised if there were other groups of extinct hominids that mingled with humans BY ZOOMMASTI report. “Modern humans and archaic humans have met many times and had many children together