Some mammals may get smaller as the planet gets hotter

Fifty-six million years ago, about 10 million years after the dinosaurs went extinct, something strange happened to our planet.

It got hot.

Really hot.

Hotter than it had ever been since the Earth formed a few billion years earlier.

Carbon signatures in the geological record show that global temperature surged 5 to 8 degrees Celsius within 10,000 years.

They also indicate that the planet’s temperature remained elevated for an additional 170,000 years before returning to normal.

Scientists describe this (relatively) rapid rise in temperature as a “hyperthermal event,” and it is not the only one that has ever occurred.

About 2 million years later, the Earth experienced another surge in temperature that was about half the magnitude of its predecessor.

Over the course of Earth’s history there have been other, smaller hyperthermal events as well. Most scientists would agree that we are in the midst of one right now.

Abigail D’Ambrosia, a graduate student at the University of New Hampshire, is interested in what happens to living things when the global temperature jumps.

Do they go extinct? Do they adapt? Do they change?

Her research, published Wednesday in the journal Science Advances, shows that at least in the case of some mammals, they shrink.

And it turns out that the amount they shrink is directly related to how hot the planet gets.

The findings are based on a new analysis of fossilized teeth and jaw fragments collected from the Bighorn Basin in northwestern Wyoming, about 80 miles east of Yellowstone National Park.

“For adult mammals, measuring teeth is a great proxy for body size,” D’Ambrosia said.

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