Scientists previously believed that the primitive southern mammoth migrated from Asia to North America around 1.5 million years ago and evolved into the Columbian mammoth.

New research shows that the southern mammoth never made it to North America, and that the Columbian mammoth's ancestor was actually the more advanced steppe mammoth, a species very similar to the Columbian mammoth that migrated from Asia into North America over the Bering Strait land bridge around 1.5 million years ago.

The researchers also found evidence that Columbian mammoths interbred with woolly mammoths, after the woolly mammoth arrived in North America around 100,000 years ago.

Lead author and Museum palaeontologist Prof Adrian Lister says: 'Until now, we thought North American mammoth evolution and adaptation ran separately from other continents. This research shows that mammoth evolution is a lot more complex and surprising.'

Teething problems

Prof Lister and Dr Andrei Sher from the Institute of Ecology and Evolution in Moscow re-examined over 600 fossil mammoth teeth held in the Museum and other collections around the world. They found that many had been misidentified.

As Columbian mammoths fed on sedge, grass and other plants on the plains of North America, their teeth were ground down, changing the shape and size of the chewing surface. This makes them difficult to distinguish from teeth of the southern mammoth, which also have low crowns and fewer enamel ridges.

The researchers mapped the changing appearance of mammoth teeth over a lifetime using micro-CT scanning at the Museum. This proved that molars identified as southern mammoth teeth were actually worn-down Columbian mammoth teeth.