Studies of tens of thousands of fossils from the La Brea tar pits in California have found no clear evidence of any of the species evolving in response to falling temperatures as ice sheets spread across the continent, or to the later warming when the glacial period ended. “They’re not fluctuating with climate change like so many biologists believe that everything must do,” says Geology Adjunct Professor Donald Prothero. “They’re static, despite obvious evidence of climate change at 20,000 years ago.”

This article was originally published by New Scientist on May 28, 2025.