Our happy hour fact to amaze your drinking buddies with.

It wasn't until our ancestors starting eating meat -- about 2.3 million years ago -- that our species started to really separate itself from other animals.

According to anthropologist Leslie Aiello of the Wenner-Gren Foundation, the vegetarian diet of early man left us lacking in the brain department. "It wasn't a very high-calorie diet, so to get the energy you needed, you had to eat a lot and have a big gut to digest it all," Aiello told NPR. "But having a big gut has its drawbacks. You can't have a large brain and big guts at the same time."

Aiello believes humans first started eating meat as scavengers -- chowing down on the same carcasses as wild dogs and hyenas would. Then, as our guts shrank and our brains were allowed to grow, we developed the smarts to design tools which aided us in more efficient meat consumption.

While it's true that vegetarians have attempted to make up for holding humanity back by releasing a steady stream of naked-lady ads, we still think a more formal apology is in order.