  As human populations grow, simple but unstable forms of co-operation evolve around activities like hunting. According to Rousseau, the central transitional moment in human history occurs at a stage of society marked by small settled communities.  At this point a change, or rather a split, takes place in the natural drive humans have to care for themselves: competition among humans to attract sexual partners leads them to consider their own attractiveness to others and how that attractiveness compares to that of potential rivals. In Emile, where Rousseau is concerned with the psychological development of an individual in a modern society, he also associates the genesis of amour propre with sexual competition and the moment, puberty, when the male adolescent starts to think of himself as a sexual being with rivals for the favours of girls and women.