Fossil Study of American Mastodons Reveals Migration Driven By Climate Change

“American mastodons repeatedly expanded into northern latitudes in response to interglacial warming.”

American mastadons were enormous elephantine mammals who went extinct approximately 11,000 years ago.

Mastodon fossil on display at the American Museum of Natural History. Credit American Museum of Natural History

Shorter than modern day elephants with a long body and covered in hair. They were much bulkier and lived in swampy and wooded areas feeding on shrubs and leaves..

They roamed across a wide expanse of landscape from Beringia (in present-day Alaska and the Yukon) east to Nova Scotia and south to Central Mexico.

It has never been really known what caused their extinction but the blame has often been laid at man’s hunting practices.

New research now points to mastodons having to move further northward due to climate changes which saw increasing competition for food supplies by animals and the actions of humans.

Mastodons were moving vast distances in response to warming climate conditions and melting ice sheets, from warmer environments, to the northernmost reaches of Alaska and the Yukon. At the same time other animals like mammoths, bison and horses were losing the valuable grass lands on which they grazed.

The new research which is  the first large-scale genetic study of American mastodons shows that the northern populations were much less genetically diverse, rendering them more vulnerable to extinction.

Hendrik Poinar, director of the McMaster Ancient DNA Centre and author on the study, said:

“The genetic data show a strong signal of migration, moving back and forth across the continent, driven, what appears to be entirely by climate.

“These mastodons were living in Alaska at a time when it was warm, as well as Mexico and parts of Central America. These weren’t stationary populations, the data show there was constant movement back and forth.”

The scientists reconstructed DNA from fossilized samples including teeth, tusks and bones.

 Emil Karpinski, lead author on the study and a graduate student at the Ancient DNA Centre and the Department of Biology at McMaster University, explained:

“By looking genetically at these animals which lived for the last 800,000 years, we can actually see the make-up of these populations that made it up to the north.

“It’s really interesting because a lot of species presently, like moose and beaver, are rapidly expanding their range northwards by as much as tens to hundreds of kilometres every century.”

Emil Karpinski, PhD Candidate, McMaster Ancient DNA Centre. Credit: JD Howell, McMaster University

This period of Earth warming saw the extinction of many of the large mammals such as mammoths, sabre-toothed cats and giant ground sloths. Mastadons were amongst the largest living on the Earth at the time.

Dr. Grant Zazula, a coauthor on the study and paleontologist with the Government of Yukon added:

“Analysis of DNA preserved in these fossil mastodon bones gives us so much more information on how these now-extinct beasts lived and died in comparison to what we know based on traditional paleontological approaches.

“These data hold the key to our understanding of how ancient animal communities like mastodons adapted to changes in the past, and provide clues to how arctic ecosystems will respond to future warming scenarios.”

The paper was published in  the journal, Nature Communications. The research was a collaboration  between scientists across Canada, the United States, Mexico, and Australia, and made possible with the help of many museums and research institutions that donated specimens for the study.

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