Research at the Yerkes National Primate Research Center has shown that gender roles may be biological among primates. Yerkes researchers studied the interactions of 11 male and 23 female Rhesus Monkeys with human toys, both wheeled and plush. The males played mostly with the wheeled toys while the females played with both types equally. http://en.wikipedia.org/wiki/Gender_role#cite_note-4Psychologist Kim Wallen has, however, warned against overinterpeting the results as the color and size of the toys may also be factors in the monkey's behavior.
Thoughts?