Mammoth's blood key

A form of "anti-freeze blood" may have helped woolly mammoths survive life in the Arctic, research suggests.

Ancestors of the extinct mammoth and modern elephants originated in equatorial Africa, scientists believe.

The blood protein haemoglobin - vital for carrying oxygen around the body - is inhibited at low temperatures. Scientists analysed preserved DNA from a 43,000-year-old mammoth whose body had been frozen in ice.

The researchers found mutations in the mammoth genes which would have enabled haemoglobin to release oxygen at low temperatures.