The term "gender" implies a wide range of things or people with common characteristics, that are differential in respect to other groups. As far as male and female genders are concerned, the literature points out several differences beside anatomic and physiologic ones: perception, spatial skills, verbal fluidity, aggression, life cycle. Hormones are partially responsible for these differences, but their action is not enough to explain their extension and variability. The different forms of social play in animals (play-fighting, chase play, play-mothering) help us to recognize the complex interaction of hormonal and social factors in developing and stabilizing these differences. So it becomes necessary to think to gender differences in terms of a conceptual system sex-gender-sexuality, that let us elude the rigid dichotomies male/female and homosexual (forbidden)/heterosexual (allowed) to focalize on biology-culture interaction, instead of supremacy of one on the other. Then it becomes possible consider and resize the strength of gender stereotypes, that tend to mortify individuality.
Keywords: Differences, gender, social play, sex, sexuality, stereotypes.