CAMBRIDGE, Mass., Dec. 20 (UPI) -- Young female chimpanzees use sticks as "dolls" more than their male peers do, like human cultures where girls play with dolls more than boys do, a study says.
Researchers say the observations, from 14 years of field work with the Kanyawara chimp community in Kibale National Park, suggest the first evidence of a non-human animal in the wild that exhibits sex differences in how it plays, ScienceNews.org reported Monday.
This finding backs up a controversial theory that biology as well as society directs boys' and girls' contrasting toy preferences.
"These new data suggest that sex differences in how children play may go way back in our evolutionary lineage and predate socialization in human cultures," anthropologist Elizabeth Lonsdorf at the Center for the Study and Conservation of Apes at Lincoln Park Zoo in Chicago says.
Young male Kanyawara chimps occasionally used sticks to mimic child care, but far more often they fought with sticks, an infrequent behavior among females, Sonya Kahlenberg of Bates College in Lewiston, Maine, and Richard Wrangham of Harvard University said.
"Although play choices of young chimps showed no evidence of being directly influenced by older chimps, young females tended to carry sticks in a manner suggestive of doll use and play-mothering," Wrangham says.
Kanyawara youngsters learned from each other to play with sticks as if caring for infants, the researchers propose, since child-bearing adult females never played with sticks and thus didn't model such behavior for younger chimps.
