The third major evolutionary leap took place around 40,000 years ago, when humans began domesticating animals by selectively breeding them for certain traits. But Shipman believes that the common explanation – humans wanted domesticated animals for food – has the story backwards.

“It takes a very long time to domesticate animals,” Shipman said. “To actually do it for the motivation of getting food, you’d have to be planning at a ridiculous time depth.”

Besides, killing a deer in the woods gets the same amount of meat as killing a deer in a fenced area, Shipman pointed out. In her view, something else must have driven humans to corral or keep animals in the first place.

Furthermore, the earliest known domesticated animal was not a delicious porker, but man’s best friend. Shipman considers humans’ strong connection with animals, rather than a desire for food, as the more likely explanation for why people decided to keep dogs around.