Read moreIn 2012, Dr. Paabo and his colleagues took samples from the bone to search for DNA. To their surprise, it held a number of genetic fragments.
“This is an amazing and shocking and unique sample,” said David Reich, a geneticist at Harvard Medical School and co-author of the new study.
The researchers used the DNA fragments to recreate a high-resolution copy of the man’s complete genome. A Y chromosome revealed that the thighbone belonged to a man.
The scientists then compared the genome of the so-called Ust’-Ishim man to those of ancient and living people.
They found that his DNA was more like that of non-Africans than that of Africans. But the Ust’-Ishim man was no more closely related to ancient Europeans than he was to East Asians.
He was part of an earlier lineage, the scientists concluded — a group that eventually gave rise to all non-African humans.
Homo sapiens, our own species, appeared in Africa around 200,000 years ago. Previous studies — both on genes and fossils — have suggested that they then expanded through the Near East to the rest of the Old World.
The Ust’-Ishim man’s genome suggests he belonged to a group of people who lived after the African exodus, but before the split between Europeans and Asians.
Dr. Paabo and his colleagues also found that the Ust’-Ishim man had pieces of Neanderthal DNA in his genome, just as living non-Africans do. But his Neanderthal DNA has some important differences.
Fossils indicate that Neanderthals spread across Europe and Asia before becoming extinct an estimated 40,000 years ago. Today, the Neanderthal DNA in each living non-African human is broken up into short segments sprinkled throughout the genome.
Dr. Paabo and his colleagues have hypothesized that this arrangement is the result of how cells divide.
During the development of eggs and sperm, each pair of chromosomes swaps pieces of their DNA. Over the generations, long stretches of DNA get broken into smaller ones, like a deck of cards repeatedly shuffled.
Over thousands of generations, the Neanderthal DNA became more fragmented. Dr. Paabo and his colleagues predicted, however, that Neanderthal DNA in the Ust’-Ishim man’s genome would form longer stretches.
And that’s exactly what they found. “It was very satisfying to see that,” Dr. Paabo said.
By comparing the Ust’-Ishim man’s long stretches of Neanderthal DNA to shorter stretches in living humans, Dr. Paabo and his colleagues estimated the rate at which they fragmented. They used that information to determine how long ago Neanderthals and humans interbred.
Previous studies — based on only living humans — had yielded an estimate between 37,000 and 86,000 years. Dr. Paabo and his colleagues have now narrowed down that estimate dramatically: Humans and Neanderthals interbred between 50,000 and 60,000 years ago, according to the new data.
waves of hominids
Read moreAs work progressed, a portrait of [9000 year old] Kennewick Man emerged. He does not belong to any living human population. Who, then, are his closest living relatives? Judging from the shape of his skull and bones, his closest living relatives appear to be the Moriori people of the Chatham Islands, a remote archipelago 420 miles southeast of New Zealand, as well as the mysterious Ainu people of Japan.
“Just think of Polynesians,” said Owsley.
Not that Kennewick Man himself was Polynesian. This is not Kon-Tiki in reverse; humans had not reached the Pacific Islands in his time period. Rather, he was descended from the same group of people who would later spread out over the Pacific and give rise to modern-day Polynesians. These people were maritime hunter-gatherers of the north Pacific coast; among them were the ancient Jōmon, the original inhabitants of the Japanese Islands. The present-day Ainu people of Japan are thought to be descendants of the Jōmon. Nineteenth-century photographs of the Ainu show individuals with light skin, heavy beards and sometimes light-colored eyes.
Jōmon culture first arose in Japan at least 12,000 years ago and perhaps as early as 16,000 years ago, when the landmasses were still connected to the mainland. These seafarers built boats out of sewn planks of wood. Outstanding mariners and deep-water fishermen, they were among the first people to make fired pottery.
The discovery of Kennewick Man adds a major piece of evidence to an alternative view of the peopling of North America. It, along with other evidence, suggests that the Jōmon or related peoples were the original settlers of the New World. If correct, the conclusion upends the traditional view that the first Americans came through central Asia and walked across the Bering Land Bridge and down through an ice-free corridor into North America.
Sometime around 15,000 years ago, the new theory goes, coastal Asian groups began working their way along the shoreline of ancient Beringia—the sea was much lower then—from Japan and Kamchatka Peninsula to Alaska and beyond. This is not as crazy a journey as it sounds. As long as the voyagers were hugging the coast, they would have plenty of fresh water and food. Cold-climate coasts furnish a variety of animals, from seals and birds to fish and shellfish, as well as driftwood, to make fires. The thousands of islands and their inlets would have provided security and shelter. To show that such a sea journey was possible, in 1999 and 2000 an American named Jon Turk paddled a kayak from Japan to Alaska following the route of the presumed Jōmon migration. Anthropologists have nicknamed this route the “Kelp Highway.”
“I believe these Asian coastal migrations were the first,” said Owsley. “Then you’ve got a later wave of the people who give rise to Indians as we know them today.”
What became of those pioneers, Kennewick Man’s ancestors and companions? They were genetically swamped by much larger—and later—waves of travelers from Asia and disappeared as a physically distinct people, Owsley says. These later waves may have interbred with the first settlers, diluting their genetic legacy. A trace of their DNA still can be detected in some Native American groups, though the signal is too weak to label the Native Americans “descendants.”
Whether this new account of the peopling of North America will stand up as more evidence comes in is not yet known. The bones of a 13,000-year-old teenage girl recently discovered in an underwater cave in Mexico, for example, are adding to the discussion. James Chatters, the first archaeologist to study Kennewick and a participant in the full analysis, reported earlier this year, along with colleagues, that the girl’s skull appears to have features in common with that of Kennewick Man and other Paleo-Americans, but she also possesses specific DNA signatures suggesting she shares female ancestry with Native Americans.
Kennewick Man may still hold a key. The first effort to extract DNA from fragments of his bone failed, and the corps so far hasn’t allowed a better sample to be taken. A second effort to plumb the old fragments is underway at a laboratory in Denmark.
The Committee to Nuke Elysium 