As seen in this video, a silverback gorilla named Ambam at the Port Lympne Wild Animal Park in the U.K. likes walking upright. Zookeepers say he does it to see over his confine’s walls, and to carry large amounts of food. Life's Little Mysteries asked Kevin Hunt, anthropologist at Indiana University and director of the Human Origins and Primate Evolution Lab, if Ambam's bipedal behavior is surprising.

"It's not unusual for chimps and gorillas to stand up, but they don't usually walk very far," he told us. "If this gorilla was a pet when he was young, he may have learned to walk upright to sort of copy the humans around him."

Apparently, Ambam's father walked on two legs a lot, too. Hunt says Ambam's father could have started life as a pet and learned to be bipedal, then Ambam could have learned the behavior from him. "Or it could be a weird personality quirk that he inherited genetically," Hunt adds.

Ambam's behavior—and ape bipedalism in general—may shed light on the evolution of bipedalism in humans' ancestors. "There's a lot of argument about why we evolved to be bipedal, but I advocate a hypothesis that it's related to food-gathering rather than looking over things," Hunt says.

"Chimps are fruit eaters. You could imagine chimps millions of years ago that were around small trees where they could reach fruits by standing on the ground and reaching up," Hunt says. "I observed chimps doing this in Gambia."

"But there's also a hypothesis that we first stood up to see over things like tall grass." This follows from the hypothesis that hominins first evolved in a grassy woodland regions in East Africa.

Ambam's zookeepers say he stands up in order to carry food in his arms as well as to look over walls, so perhaps he provides evidence in favor of both hypotheses about the evolution of bipedalism.

This article was provided by Life's Little Mysteries, a sister site to LiveScience.