Scientists armed with new technology have successfully mapped the genes of an extinct humanoid species that may have lived in the Philippines tens of thousands of years ago.
The scientists have conducted a high-precision genetic sequencing of the extinct Denisovan people, a relative of humans, the journal Science reported. An earlier study of Denisovan DNA showed that the species interbred with —and passed on genes to— humans in Asia, including the Philippines. "Aboriginal Australians, Near Oceanians, Polynesians, Fijians, east Indonesians, and Mamanwa (a 'Negrito' group from the Philippines) have all inherited genetic material from Denisovans," the study said.
Asians' Denisovan heritage
According to an LA Times report, the study found "three to five percent of the DNA in people native to Papua New Guinea, Australia, the Philippines and other islands nearby came from Denisovans."
However, the report said the authors of the study did not find any significant contribution of Denisovans to the DNA of people from mainland Eurasia.
Still, it quoted the scientists as saying that an analysis of the genome and comparisons with ours and that of neanderthals —another now-extinct humanoid species that lived alongside our ancestors— will offer insights into the history of Homo sapiens.
Tracing humanity's past
The insights may include "who we mated with, where and when — as well as the unique genetic changes that make modern humans who they are," the report quoted the scientists as saying.
But study leader Svante Paabo, a pioneer in decoding ancient genomes, said it may take biologists decades to understand the meaning of all these tiny differences.
"Many of them may have no function — but among them will undoubtedly hide some crucial changes that are essential for what made modern human history possible," said Paabo, director of the department of evolutionary genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
The Denisovan genome
The Denisovan genome was derived from tiny quantities of shredded DNA extracted from a finger bone found in a Russian cave in 2008 and a tooth found later.
Also, the analysis suggests the Denisovans had dark skin, brown hair and brown eyes, but scientists cannot say much more beyond that for now.
But scientists said what is striking is that the genome is as detailed as a sequence generated with a fresh blood or saliva sample from someone alive today.
The scientists banked on new techniques to investigate scant and highly degraded genetic material found in fossils.
John Hawks, a paleoanthropologist at the University of Wisconsin in Madison, said their application to these and other specimens promises to draw back the curtain on our species' complicated and much-debated history.
Genetic differences mapped
Paabo and his colleagues have highlighted several intriguing genetic differences between modern humans and our primitive relatives that could prove significant.
Such differences may include genes involved in wiring the brain and ones that may be linked to autism.
The new gene-sequencing techniques also allowed scientists to more precisely calculate how much of modern humans' DNA came not from Denisovans but Neanderthals.
"They found, to their puzzlement, that Native Americans and people in East Asia have more Neanderthal DNA than do people whose ancestors are from Europe, where most Neanderthals lived," the LA Times report said.
That is "really, really interesting," said study coauthor David Reich, a geneticist at Harvard Medical School in Boston.
Undiscovered ancient relatives?
Hawks also said it is very likely that modern humans have other undiscovered ancient relatives whose fossilized bones can reveal more secrets.
"It's got to be just the beginning," Hawks said.
The LA Times report also said the new genome gives scientists a sense of just how much of our genomes we owe to our extinct relatives.
Michelle Glantz, a biological anthropologist at Colorado State University in Fort Collins who was not involved in the study, said the part of the world where the Denisovan fossils were discovered could contain a particularly rich trove of archaic humans.
The LA Times said other intriguing finds from Central Asia included a fossil from Uzbekistan with a Neanderthal-like inner ear and a cranium resembling a modern human's.
But it will take a lot more than DNA data to piece together the picture there, she said.
Evolutionary path
Scientists have so far determined that ancestors of humans emerged in Africa and migrated out to the rest of the world in successive waves.
It said the first globe-trotter was Homo erectus, whose trek began one to two million years ago.
Following them were the ancestor of the Neanderthals and Denisovans, who left Africa as far back as 800,000 years ago and replaced or interbred with descendants of Homo erectus.
The third wave of people, Homo sapiens, left Africa about 100,000 years ago and sometimes mated with the Neanderthals and Denisovans they encountered.
"The result is you and me and everyone else on the planet," the LA Times report said. — TJD/HS
