Origin of the Columbian mammoth revealed

New research shows the Columbian mammoth evolved directly from the Eurasian steppe mammoth, as the species made its way from Asia to North America some 1.5 million years ago. Research led by the Natural History Museum and published in Science today suggests that the steppe and Columbian mammoths are virtually the same species.

Columbian mammoths were thought to have evolved in North America from southern mammoths, the original Eurasian species that roamed our planet 2.5-1.0 million years ago. Yet it appears the southern mammoth never reached North America. The Columbian mammoth arrived there 'ready-made' having attained all its key features in eastern Asia. Later interbreeding with populations of immigrant woolly mammoths helps explain North America's remarkable variety of late ice age mammoth fossils.

Lead author Professor Adrian Lister, fossil mammal researcher at the Natural History Museum says: 'Mammoths are an excellent example of how environmental change shapes the origins and diversity of species on our planet over time. This study shows the value of fossil collections in helping us understand the diversity of life, hand-in-hand with genetic evidence.'

'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.'

The scientists used over 600 fossils of the upper and lower teeth belonging to the southern, steppe, columbian and the woolly mammoth. These fossils, from the Museum's collection and other international museum collections were used to study the differences in molar and skull structure amongst species.

Using cutting-edge micro-CT scanning at the Museum, the scientists mapped the changing appearance of a tooth through life. They reinterpreted many American fossils previously identified as southern mammoth as worn molars of Columbian mammoth. Molars of southern mammoth have low crowns and fewer enamel ridges, but those of other species can be mistaken for them when worn down through the animal's life. Many southern mammoth fossils in museums will need relabelling as either steppe or Columbian species.

Mammoths evolved significantly after arriving in Eurasia from Africa around three million years ago, with the shape of their teeth and skulls adapting to grazing the increasingly open habitats of the Pleistocene. Although this pattern has been well documented for Eurasia, the evolution of North American mammoth fossils had been much less clear.

The woolly mammoth evolved later than the Columbian mammoth in the same Beringian region linking North America and Asia. It then spread into Europe and North America, leading to a diversity of mammoth types as it encountered remaining groups of the steppe and Columbian species. This shows how interbreeding, or hybridisation, causes species boundaries to shift through time and generates further diversity.

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