Early humans lived in Papua New Guinea highlands 50,000 years ago

Archeologists have evidence suggesting that early humans braved cold temperatures to occupy highlands in Papua New Guinea 50,000 years ago in search of food.

Working on five archeological sites about 2,000 metres above sea level, researchers from Papua New Guinea, Australia and New Zealand found charred nut shells from the pandanus tree and stone tools which carbon dated back to 50,000 years ago.

"This is the first evidence of people at such a high altitude at the earliest of time," said anthropology professor Glenn Summerhayes at the University of Otago in New Zealand.

Experts have long assumed that the earliest humans left Africa and then moved along warmer coastal areas to occupy the rest of the planet, but Summerhayes said their findings showed that wasn't necessarily the case.

"It's testimony to human adaptability. We assumed (before) that the earliest modern people were conservative, adapted to a warmer coastal climate and this allowed them to spread across the planet quite quickly," said Summerhayes, lead author of the paper which was published on Friday in Science.

"Well, here we have evidence that they were really quite adaptable, moving up to a high altitude environment in search of pandanus, which means they had a knowledge of plant use beforehand," he said in a telephone interview.

The pandanus tree produces useful leaves and pineapple-like fruit. The researchers also found starch grains from yams, which they believe were probably collected from their natural growing sites at lower, warmer, altitudes.

The early settlers cleared land on the highlands to cultivate these plants, Summerhayes said. Stone axes found were likely to have been used for cutting vegetation and clearing forest patches to let in sunlight and to grow food and other useful plants.

Temperatures at that altitude hit 20 degrees Celsius at the hottest part of the day and plunge to freezing point at night.

"They would have to wear some sort of clothing. If you didn't have clothing up there, you would die of hypothermia," he said.

The early colonisers would have needed to make two water crossings to get from southeast Asia to Sahul, which was the single land mass that made up of Australia, Papua New Guinea and Tasmania before it broke up 10,000 years ago.

"It doesn't occur in one or two years but over a period of time. I think that human technology was such that they could make repeat voyages over the sea straits, but the nature of the voyages or sea craft I don't know," Summerhayes said.