Actors Stan Laurel and Edna Marlon play at socializing around the campfire. It turns out that early man's brain developed in part thanks to cooking. Hulton Archive/Getty hide caption

itoggle caption Hulton Archive/Getty

Megan Lutz, left, and Justin Chun react to amateur comedian Robert Lynch at the Metropolitan Room in Manhattan, N.Y. Lynch is an anthropologist researching what laughing reveals about us. Melanie Burford for NPR hide caption

itoggle caption Melanie Burford for NPR

Gorillas are fine with being herbivores, like this one at a Seattle zoo. But humans evolved as omnivores. Is diet destiny? Ted S. Warren/AP hide caption

itoggle caption Ted S. Warren/AP