By Paul Rincon
BBC News Online science staff
Humans occupied the freezing lands high above the Arctic Circle during the last Ice Age, say Russian archaeologists.
One of the spear foreshafts was made from a woolly rhino horn
New Stone Age artefacts from Yana in northern Siberia have pushed back the human presence in the Arctic by around 16,000 years, surprising many experts.
The finds also hint that North America may have been populated much earlier than thought given the dig's relative proximity to the Bering Strait.
Full details of the discoveries appear in the academic journal Science.
Vladimir Pitulko from the Institute for the History of Material Culture in St Petersburg, Russia, and others have uncovered numerous artefacts and animal bones in frozen deposits from an ancient terrace by the Yana River.
The artefacts, made by modern humans (Homo sapiens), include spear "foreshafts" and stone tools.
The finds suggest humans may have been hunting big game animals in the region by around 30,000 years ago.
Resilience and ingenuity
Foreshafts are the long part of the spear that humans attached spear-points to before hurling them at prey. They allowed hunters to replace broken spear-points quickly and throw the spear again.
Two of the foreshafts are made from mammoth ivory, while another is relatively unusual in being fashioned from the horn of a woolly rhino.
The animal bones found at the site belong to mammoths, bison and horses amongst others.
"This site shows that people adapted to this harsh, high-latitude, Late Pleistocene environment much earlier than previously thought," the authors write in Science.
Around 30,000 years ago, human hunters would have needed all their resilience and ingenuity to survive in this freezing environment, especially during winter.
The Yana River valley is about 500 kilometres above the Arctic Circle. The artefacts found at the site date to a time when the climate was in the process of cooling down, turning open meadows into icy tundra.
Stone tools at the site show the hunters were sophisticated
"It's about as far north as you can get; it's pretty neat. I think it's a very significant site," said Professor Dennis Stanford, of the Smithsonian Institution in Washington, US.
But it is impossible to know how long humans inhabited the region for, or indeed whether they lived there at all. They may simply have made excursions here from bases in warmer climes.
Intriguingly, the authors suggest that the foreshafts they used bear a similarity to those of the Clovis people, long regarded as the first human settlers of North America.
There is scant evidence for a human presence there prior to 14,000 years ago.
The first colonists are thought to have crossed into the New World from Asia when a fall in sea levels at the height of the last Ice Age formed a land bridge, known as Beringia, between the two continents.
To some researchers, the observation that people had adapted to living in the Arctic by 30,000 years ago raises the possibility that settlers could have reached North America even earlier. But the suggestion is highly controversial.
"I don't think it has anything to do with the populating of America," said Stanford.
"They're comparing [the foreshaft] to something which is 15,000 years older than Clovis - twice as old as Clovis. And it is widespread over Europe and Asia [in the Upper Palaeolithic]."