Australian researchers have "resurrected" part of the blood of an extinct woolly mammoth, revealing how these giants were able to survive the freezing Arctic.
They recreated the oxygen-carrying protein, haemoglobin, from mammoth DNA found in the Siberian permafrost.
The director of the Australian Centre for Ancient DNA at the University of Adelaide, Alan Cooper, said it was the first experiment of its kind.
"It's the same as the protein you would get if you went back 30,000 years and stuck a needle in a mammoth and got its blood," he said. "We effectively brought it back to life."
The ancestors of modern elephants and mammoths evolved in a warm climate in Africa about 7 million years ago. Mammoths were the only branch of the family to migrate north successfully into the colder parts of Europe about 1.2 to 2 million years ago, evolving small ears and tails, and a woolly coat to conserve heat.
Professor Cooper said human haemoglobin does not release oxygen well in freezing conditions, which starves extremities of oxygen, leading to frostbite and gangrene.
The research showed, however, that mammoth haemoglobin had a radically different structure which meant it still worked well in cold temperatures.
This would have helped the Ice Age mammals survive because they did not have to waste energy keeping their extremities, including their all-important trunks, warm. "We can see how evolution worked in real time to come up with this strategy."
Professor Cooper said the exciting possibility is that their approach could be used on other extinct species, such as our close extinct relatives, Neanderthals.
Sequencing the Neanderthal genome will be completed soon, revealing the genetic codes for their proteins, which may be different to ours. Recreating the proteins and studying their properties might throw light on human diseases, he said.
The mammoth study by the international team, including Kevin Campbell of the University of Manitoba in Canada, is published in the journal Nature Genetics. Researchers first worked out the mammoth's haemoglobin genes sequence from DNA found in bones of a 43,000-year-old specimen in Siberia.
Elephant genes were altered to match the mammoth genes, before being inserted into bacteria which then produced the mammoth haemoglobin.
A variety of tests were carried out to determine its different characteristics, including the insensitivity to cold.