Genetic Evidence From Fossilized Remains Show Climate Change Drove Mastodons Vast Distances Across North America


Artistic rendering of mastodons. Credit: Julius Csotonyi

New research from an international team of evolutionary geneticists, bioinformaticians, and paleontologists suggests that dramatic environmental changes accompanying the shift or melting of continental glaciers played a key role as American mastodons moved north from their southern ranges.

In the first large-scale genetic study of American mastodons, published today in the journal, Nature Communications, researchers reconstructed complete mitochondrial genomes from the fossilized remains of 33 individual animals. The species went extinct approximately 11,000 years ago during the megafaunal extinctions that took out many of the large mammals such as mammoths, saber-toothed cats, and giant ground sloths.

The mastodon was among the largest living land animals on Earth at the time, roaming from Beringia (present-day Alaska and the Yukon) east to Nova Scotia and south to Central Mexico. They were primarily browsers, living in swampy settings, eating shrubs, and low-hanging tree branches.

New research from an international team of scientists suggests that dramatic environmental changes accompanying the shift or melting of continental glaciers played a key role as American mastodons moved north from their southern ranges. Credit: McMaster University

“The genetic data show a strong signal of migration, moving back and forth across the continent, driven, what appears to be entirely by climate,” says evolutionary geneticist Hendrik Poinar, director of the McMaster Ancient DNA Centre and author on the study.

“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,” he says.

There has been much speculation about what caused their extinction, along with 44 other large mammals, though many scientists believe it was a combination of climate change, increasing competition for food sources and overhunting by early humans.

Museum Mastodon

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

Dramatic and repeated temperature fluctuations occurred routinely on the planet for millions of years — the most dramatic of which over the last 800,000 years — resulting in ice-sheet expansion and retraction and the warming of previously frozen northern regions whose new forests and wetlands provided new food sources for some animals like the mastodon, moose, and beaver, but took away grasslands from others like horses, mammoths, and bison.

Researchers suggest that by examining how different ecologically adapted Pleistocene megafauna responded genetically and ecologically to such climate transitions can provide valuable information on how climate change is affecting modern-day species in the north.

Emil Karpinski

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

For the study, the team teased out and reconstructed DNA from fossilized samples including teeth, tusks, and bones.

Analysis show that 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. However, despite these massive increases in the territory, northern populations were much less genetically diverse, rendering them more vulnerable to extinction.

“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 kilometers every century,” says Emil Karpinski, lead author on the study and a graduate student at the Ancient DNA Centre and the Department of Biology at McMaster University.

“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”, says Dr. Grant Zazula, a coauthor on the study and paleontologist with the Government of Yukon.

For more on this research, read Climate Change Drove Mastodons to Migrate Vast Distances Back and Forth Across North America.

Reference: “American mastodon mitochondrial genomes suggest multiple dispersal events in response to Pleistocene climate oscillations” by Emil Karpinski, Dirk Hackenberger, Grant Zazula, Chris Widga, Ana T. Duggan, G. Brian Golding, Melanie Kuch, Jennifer Klunk, Christopher N. Jass, Pam Groves, Patrick Druckenmiller, Blaine W. Schubert, Joaquin Arroyo-Cabrales, William F. Simpson, John W. Hoganson, Daniel C. Fisher, Simon Y. W. Ho, Ross D. E. MacPhee and Hendrik N. Poinar, 1 September 2020, Nature Communications.
DOI: 10.1038/s41467-020-17893-z

The paper 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 this study.

6 Comments on "Genetic Evidence From Fossilized Remains Show Climate Change Drove Mastodons Vast Distances Across North America"

  1. When trying to look at what the future may bring to our planet from what has happened in the past makes absolutely no sense because what the future holds for this planet is entirely different from the past because we humans have destroyed Earth’s past environmental conditions and replaced the Earth’s environment with an environmental that allows the Sun to conquer and destroy natures natural forces that protects life on Earth from the deadly hot rays of the Sun. There is a constant battle between planets and Suns for life throughout the universe. As far as we know this is the only planet where a bubble, which we call an atmosphere, was create to make it possible for the Sun to not bake this planet into looking like every other floating rocks of all sizes flying around in space. We have destroyed that bubble to the point where that bubble can no longer produce enough of these things we call clouds which are really the only thing that protects the Earth’s surface from the hot rays of the Sun. Without those clouds up there we would all be cooked millions of years ago. Without clouds all life could not exist on Earth. Clouds give us rain to replace the water that the Sun daily evaporates from the Earth. However today we don’t have many clouds up there anymore and that Sun is baking our Earth a heck of a lot more than usual. I have a lot more that I have written about this if you care to read on FaceB.

  2. This is all bs

  3. Fascinating what can be gleaned from dna. Any reader who gives no credence to such work and dismisses the stories told by mDNA and forensic techniques are afraid of something. Perhaps basic understanding of genetics and the the rigor of science is beyond comprehension of the ‘quick to dismiss’. Simply knowing what it takes to make the cut for publishing findings in scientific journals is perhaps one place to start for the poor souls that think there is an agenda to anything they read. Good work in this story!

  4. Adam D Laurendine | September 10, 2020 at 4:08 pm | Reply

    It was all of those SUV’s the cavemen were driving.

  5. many of them now live in Washington DC

  6. Interesting but… AssCLOWNZ*

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