Here’s a simple lesson from a new study: evolution is sloooooooooow.

[Evolutionary biologist] Nikos Solounias helped develop a methodology known as dental mesowear analysis to reconstruct the diets of extinct species by measuring food-related wear and tear on fossil teeth. He and [Matthew] Mihlbachler used the process to investigate wear patterns on the molars of thousands of fossil horses. They later analyzed their data alongside records of North American climate changes that would have shifted the animals’ diets from rainforest fruits and woody, leafy vegetation to the more abrasive diets found in grasslands.

“Lag time in the evolution of horse teeth in comparison to dietary changes is critical,” Mihlbachler explained. “We found that evolutionary changes in tooth anatomy lag behind the dietary changes by a million years or more.”

(H/T: Bil Danielson)