Shortly after an asteroid strike triggered a cataclysmic extinction event 66 million years ago, a group of mammals with a proclivity for climbing trees and eating fruit began to thrive. These animals—the early relatives of primates—would give rise to a lineage that led to the first monkeys, including great apes such as gorillas, chimpanzees, and eventually, humans.

Now, scientists have discovered fossils of the oldest known primate among a cache of unusual teeth tucked away in a museum drawer for decades. Some of these teeth, recently described in the journal Royal Society Open Science, belonged to the new species Purgatorius mckeeveri, a pint-sized precursor to modern primates that lived 65.9 million years ago, just 100,000 years after the extinction event