A group of chimpanzees travels through the woodlands of Gombe National Park, Tanzania, where Jane Goodall first began studying their kind back in 1960. They come upon red colobus monkeys.

Chimps survey their prey. A hunt begins. Chaos ensues as monkeys fall from trees to the screams of chimps as they make their kill—all of it caught on video.

Ian Gilby, an anthropologist at Arizona State University and leader of a new study on the subject, originally filmed members of the habituated Kasekela chimp community in Gombe to learn more about how they share meat.

Reviewing the videos later, he noticed that chimps eat subadult prey—infants, juveniles, and adolescents—heads first. Chimps consuming adult prey show less of a pattern, he found.

This left him with a little-studied question that's relevant to how humans evolved: Why would the apes prefer to eat a particular body part first?

Brain Food

Gilby thinks it has to do with nutrition.

“We tend to just say meat is meat, but we know that the nutrient composition varies," says Gilby, whose study appeared recently in the International Journal of Primatology. "The whole carcass is valuable, but the brain is especially valuable."

Brains are high in fat and a source of long-chain fatty acids, which aid in neurological development.