Fossils show that mammoth species interbred helping them to survive dramatic climate shifts

• Two mammoth molars found in Canada reveal that there was long-term hybridisation between wooly mammoths and Columbian mammoths
• The findings show how interbreeding is an important factor in evolution
• Assessing how mammoths adapted to the changing conditions of the Ice Age can help scientists understand how other animals might adapt to modern climate change

Scientists have uncovered new evidence that woolly mammoths and Columbian mammoths repeatedly interbred in North America, reshaping our understanding of how these Ice Age giants evolved in response to dramatic climate shifts.

Adapted to different climates and food sources, it was assumed that the woolly mammoth, living in what is now Canada and the northern USA, and the Columbian mammoth, found further south, lived largely independent lives.

However, following the analysis of two teeth from separate mammoths from British Columbia, Canada, an international team which included Prof. Adrian Lister from the Natural History Museum and scientists from the Centre for Palaeogenetics, Sweden, has shown that there was in fact long-term hybridisation between these two species.

Prof. Adrian Lister, mammoth expert at the Natural History Museum, said, “These findings contribute to a growing understanding that hybridisation has been an important factor in evolution. In fact, many species have arisen this way – which isn’t the standard Darwinian idea of how evolution happens. We think of a lineage changing through time, and a branching tree with species diverging, but what can happen is a cross link with two species hybridising and producing a new branch.

The research published in the journal Biology Letters shows that woolly mammoths expanded south into North America during glacial periods, coming into contact, and breeding with, Columbian mammoths. Due to the later of the two fossils having more Columbian mammoth DNA than the other, the team have concluded that Columbian and woolly mammoths must have bred many times over thousands of years.

The study builds upon knowledge from a paper released in 2021 where 1.2-million-year-old DNA extracted from a steppe mammoth tooth found in Krestovka, Siberia, showed how a distinct group of steppe mammoths bred with woolly mammoths, producing the Columbian mammoth.

It is likely this interbreeding happened in North America after both mammoth species crossed a now-submerged land bridge between Siberia and Alaska. As a result, as much as half of the DNA of Columbian mammoths was inherited from woolly mammoths.

The new study shows that some woolly mammoths were also inheriting Columbian mammoth genetics.

This combination of genetic and morphological analysis allowed the team to build a more complete picture of mammoth evolution. Whilst the hybrid mammoths were found to be genetically distinct from other members of their species, their teeth were surprisingly similar to those of the woolly mammoth, which had the same use for teeth adapted to eating grasses on cold, open plains. Similarly for hybrid Columbian mammoths living further south, there was a pressure for these animals to keep their more generalist teeth despite having significant amounts of woolly mammoth DNA.

Assessing how mammoths adapted to the changing conditions of the Ice Age can also help scientists understand how elephants, and other animals, might adapt to modern climate change.

Adrian added, “Understanding how species can mitigate environmental change is very important at the moment, and we can look to past climate change to help with that. We know that mammoths ultimately didn’t survive the end of the Ice Age, and delving into their adaptability could help us better understand why.”

This research is cross thematic, sitting across both the Evolution of Life and Genomics research themes at the Museum that aims to reveal the causes and consequences of evolutionary and environmental change, which are central to understanding life on Earth.

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