By SETH BORENSTEIN
WASHINGTON (AP) — Global warming shrank certain animals in the ancient past, and scientists think it could happen again.
Warm-blooded animals got smaller at least twice in Earth’s history when carbon dioxide levels soared and temperatures spiked as part of a natural warming, a new study says.
University of New Hampshire researcher Abigail D’Ambrosia warned that mammals — but not people — could shrivel in the future under even faster man-made warming.
“It’s something we need to keep an eye out for,” said D’Ambrosia, who led the new work. “The question is how fast are we going to see these changes.”
Three different species shrank noticeably about 54 million years ago when the planet suddenly heated up. One of them — an early, compact horse — got 14 percent smaller, going from about 17 pounds to 14.6 pounds, according to an analysis of fossil teeth in Wednesday’s journal Science Advances .
“These guys were probably about the size of maybe a dog, then they dwarfed,” said D’Ambrosia. “They may have gone down to the size of a cat.”
Another creature that contracted was a lemur-like animal that’s the earliest known primate. It shrank about 4 percent; while it may not seem like much, it’s noticeable because studies of the animal over millions of years showed it was usually getting bigger over time, D’Ambrosia said.
Previous studies have documented a similar shrinking of mammals, including another early horse ancestor, during an earlier warming about 56 million years ago. Scientists and farmers have also long tracked animals, such as cows, that shrink and give less milk during hotter stretches.