The remains of fires, stone tools and food surface at six campsites dating back up to 49,000 years.
The oldest high-altitude human settlements ever discovered have been found in volcanic ash in Papua New Guinea.
The findings suggest that the prehistoric highlanders made stone tools, hunted small animals and ate yams and nuts.
The world's oldest known high-altitude human settlements, dating back up to 49,000 years, have been found sealed in volcanic ash in Papua New Guinea mountains, archaeologists said Friday.
Researchers have unearthed the remains of about six camps, including fragments of stone tools and food, in an area near the town of Kokoda, said an archaeologist on the team, Andrew Fairbairn.
"What we've got there are basically a series of campsites, that's what they look like anyway. The remains of fires, stone tools, that kind of thing, on ridgetops," the University of Queensland academic told AFP. "It's not like a village or anything like that, they are these campsite areas that have been repeatedly used."
Fairbairn said the settlements are at about 2,000 meters (6,600 feet) and believed to be the oldest evidence of our human ancestors, Homo sapiens, inhabiting a high-altitude environment.
"For Homo sapiens, this is the earliest for us, for modern humans," he said. "The nearest after this is round about 30,000 years ago in Tibet, and there's some in the Ethiopian highlands at around about the same type of age."
Fairbairn said he had been shocked to discover the age of the finds, using radio carbon dating, because this suggested humans had been living in the cold, wet and inhospitable highlands at the height of the last Ice Age.
"We didn't expect to find anything of that early age," he said.
The findings, published in the journal Science, suggest that the prehistoric highlanders of Papua New Guinea's Ivane Valley in the Owen Stanley Range Mountain made stone tools, hunted small animals and ate yams and nuts.
But why they chose to dwell in the harsh conditions of the highlands, where temperatures would have dipped below freezing, rather than remain in the warmer coastal areas, remains a mystery.
"Papua New Guinea's mountains have long held surprises for the scientific community and here is another one -- maybe they were the home of Homo sapiens' earliest mountaineers," Fairbairn said.