"I favour the hypothesis that stick carrying is practice for the adult role of motherhood. perhaps similar to functions of other kinds of play, being practice for adult roles … It was striking that this behaviour was seen in some adult females, but never after they became mothers."
—Zoologists Sonya Kahlenberg of Bates College, who, with her colleague Richard Wrangham of Harvard University, observed juvenile chimps in Uganda's Kibale National Park playing with sticks "like children play with dolls, cradling them and even making nests for them to sleep in at night." I wish I had some juvenile chimps in my family. They seem very easy to please. ("Merry Christmas! Here, I got you a stick.") Of course, it would make punishing the naughty ones more difficult. Since they'd probably be all like, "Yay! Coal! Look, it's my new coal doll!" And, of course, when they're older, they want video games.
Photo by Piotr Jaczewski, from Flickr.