The shapes of fossilized teeth from 65.9 million-year-old, squirrel-like creatures suggest that the branch of the tree of life that gave rise to us humans and other primates flowered while dinosaurs still walked the earth. That’s the claim coming from a team of 10 researchers across the U.S., including biologists at Seattle’s Burke Museum and the University of Washington.
In a study published by Royal Society Open Science, the team lays out evidence that an ancient group of primates known as plesiadapiforms must have emerged before the mass-extinction event that killed off the dinosaurs. (Technically, modern-day birds are considered the descendants of dinosaurs, but that’s another story.)
The evidence comes from an analysis of tooth fossils that were unearthed in the Hell Creek area of northeastern Montana.