Woolly mammoths were equipped with a type of biological anti-freeze which enabled them to survive in the Arctic, researchers have found.
The evolutionary trump card saved the animals from freezing to death and made them masters of their environment.
Scientists extracted DNA from the remains of a mammoth that died 43,000 years ago in Siberia. They discovered that the haemoglobin in mammoth blood had three genetic mutations that allowed it to distribute oxygen efficiently in cold temperatures to the parts of the body that needed it. Haemoglobin delivers oxygen around the body but in most animals it is hampered as the conditions get colder.
As an animal that evolved in equatorial Africa about 6.7 to 7.6 million years ago, roughly the same time as modern elephants, it would have had no need to cope with the cold.
But as it moved out of Africa and eventually colonised Arctic regions about 1.2 to 2 million years ago - just as abrupt changes in the climate caused temperatures to plunge - it needed adaptations.
Smaller ears and tails were among the adaptations, as was the growth of thick fur, and it now seems the mammoth also underwent genetic mutations that led to it having three different types of amino acids to those produced by its tropical cousins.
The researchers, led by Dr Kevin Campbell, from the University of Manitoba in Winnipeg, Canada, reported in the journal Nature Genetics: “We have identified physiological properties of woolly mammoth haemoglobin that may have played an important role in the adaptation of this African-derived lineage to Arctic environments.”
The changes are similar to ones seen in other mammals living in Arctic conditions, such as reindeer and musk oxen.
Professor Michi Hofreiter, from the University of York, took part in the research, and said: "Our study is the first one to reconstruct an evolutionary important, adaptive trait from an extinct species using ancient DNA.”