A new study finds that young females in one group of African chimpanzees use sticks as dolls more than their male peers do, often treating pieces of wood like a mother chimp caring for an infant. In human cultures around the world, girls play with dolls and pretend that the toys are babies far more than boys do.

Ape observations, collected over 14 years of field work with the Kanyawara chimp community in Kibale National Park, provide the first evidence of a nonhuman animal in the wild that exhibits sex differences in how it plays, two primatologists report in the Dec. 21 Current Biology.