Pronghorn are among the fastest animals on Earth. Often ranked second to the cheetah for mammalian land speed records, America’s peculiar giraffoid has been said to hit top speeds over 50 miles per hour and maintain their sprints for much longer than quick carnivores. The exact figure has been difficult to pin down, but the swiftness of pronghorn in full sprint leaves no doubt that these herbivores are easily capable of outpacing coyotes and other potential predators. But why should pronghorn be so much faster than North America’s carnivores? The answer, some researchers have speculated, lies in prehistory.

Today’s pronghorn species – Antilocapra americana – is the