Have researchers discovered new strands of hominid DNA in people living in Melanesia? That’s one of the questions raised in a recent article in Science News, the magazine of The Society for Science & the Public.
According to new human DNA research conducted by Ryan Bohlender, a statistical geneticist at the University of Texas MD Anderson Cancer Center in Houston, “Traces of long-lost human cousins may be hiding in modern people’s DNA.”
Bohlender and others believe indigenous peoples living in Australia and Melanesia — a region in the south Pacific that includes Papua New Guinea and several nearby islands — “may carry genetic evidence of a previously unknown extinct hominid species,” Science News reports.
Previous models show humans evolving from Neanderthals and Denisovans, “an extinct distant cousin of Neanderthals,” Science News explains.
DNA data offer evidence of unknown extinct human relative https://t.co/vtkZ9KBrd4
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While Neanderthal DNA has been discovered throughout Europe and Asia, only a single fossil of a finger bone found in Siberia contains Denisovan DNA.
People of European and Asian descent still carry approximately 2.8 percent Neanderthal DNA, while people descended from Africa do not carry any. Likewise, Europeans carry no Denisovan DNA, while some Asians carry a “tiny amount.” Roughly 0.1 percent, according to Bohlender’s research. People in Papua New Guinea have similar amounts of Neanderthal DNA, approximately 2.74 percent, but Denisovan DNA appears to account for 1.11 percent of their DNA as well.
The unusually high levels of Denisovan DNA, and the fact that it’s not a direct match to that of the Siberian sample, led Bohlender and his colleagues to conclude that a third, and previously unknown, group of hominids had bred with the ancestors of Melanesians.
“Human history is a lot more complicated than we thought it was,” Bohlender told Science News.
Bohlender’s belief in the possibility of a third form of hominid DNA showing up in human DNA is supported by a previous study conducted by the Natural History Museum of Denmark. In that study, researchers examined DNA from 83 Aboriginal Australians and 25 people from the highlands of Papua New Guinea, Science Alert reports.
Science Alert says that based on that research, “DNA that was very similar to that of the Denisovans, but distinct enough for the researchers to suggest that it could have come from a third, unidentified hominid.”
However, not everyone is completely on board with Bohlender’s theory. Mattias Jakobsson, an evolutionary geneticist at Uppsala University in Sweden, explained to Science News that because there is only one sample of confirmed Denisovan DNA available, researchers still know very little about the species or how diverse it was. In Jakobsson’s view, it is just as likely that the Denisovan-like DNA showing up in New Guinea and Australia is simply “a different branch of Denisovans” that interbred with earlier Melanesians.
This theory relies on the possibility that as Denisovans spread throughout different regions of the world, their DNA evolved over time, making it appear to be that of a distinct species rather than simply a variant.
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Elizabeth Blue, a statistical geneticist at the University of Washington in Seattle, seconds Jakobsson’s theory, arguing that it may very well be the case that Denisovans were so widespread and diverse that in the absence of more DNA samples it remains difficult to accurately identify them in some cases. Blue cites the fact that Europeans and Asians are genetically distinct despite descending from the same Neanderthal species to support this idea.
Blue concedes, however, that if evidence that Denisovans were genetically similar throughout multiple regions and over time, it would support Bohlender’s conclusions.
Even Bohlender acknowledges there are multiple possibilities to explain the different strand of DNA found in Melanesians.
“We’re missing a population or we’re misunderstanding something about the relationships,” Bohlender told Science News.
It will require further research to make conclusive ruling on whether the unknown DNA in the Melanesians is in fact indicative of a previously unknown pre-human hominid or it is simply a variant of Denisovan DNA.
[Featured Image by Matt Turner/Getty Images]