"No one seriously believed that there was some type of fence in Uzbekistan that would have kept them from moving further to the east—we just didn't have the evidence one way or the other," said Leslie Aiello, an anthropologist at the Wenner-Gren Foundation for Anthropological Research in New York, who wasn't involved in the study.
"I think we can be cautiously confident that these fossils came from European Neandertal stock."
Carbon dating of the Siberian bone fragments places them between 30,000 and 38,000 years old—near when the Neandertals are thought to have disappeared from the fossil record—but it is possible that they ventured east long before then.
(Related: "Neandertals' Last Stand Was in Gibraltar, Study Suggests" [September 13, 2006].)
"The environment of the Altai between 35,000 and 50,000 years ago is known to have fluctuated considerably, from conditions similar to the present day through to very cold steppe-tundra," said Chris Stringer, a paleoanthropologist at the Natural History Museum in London, who wasn't involved in the study.
"It seems likely that the Neandertals periodically extended their range to these regions when conditions allowed, and retreated or died out when they deteriorated again."
Aiello of the Wenner-Gren Foundation agreed.
The Neandertals "may have been occupying these regions during the warmer climate fluctuations and not during the really cool snaps, or perhaps during the summers and not the winters," she said. "We really don't know."
Another possibility is that the Neandertals took advantage of a warm period around 125,000 years ago, when the Caspian Sea was drastically reduced in size.
"This may have facilitated the expansion of the Neandertals into central Asia and southern Siberia," study leader Pääbo said.
To Mongolia and Beyond
Given that the Neandertals got as far as Siberia, there is no reason why they might not have gone further still, experts said.
"I have no doubt that Neandertals could have migrated further to the east—to Mongolia or China," Aiello said. "There would have been nothing to stop them."
Little archaeological work has been done in the Far East on the topic, but archaeologists are excited at the prospects.
"There is one intriguing fragmentary skull from Maba in China [Guandong Province] which does show some Neandertal resemblances," Stringer, of the Natural History Museum, said.
"It would be interesting to see if it had any ancient DNA, and whether this was Neandertal-like or represented another distinct lineage of early humans."
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