Discusses parallels between the reduction of sexual dimorphism and the evolution of human social behavior (division of labor, dominance vs subordination relationships between the sexes, gender differences in mental qualities, partner choice, and parental investment). Ontogenetic trends that shape gender stereotypes in society are discussed. Characteristics of social behavior including frequencies of performed and received aggression, help, avoidance, demonstrations, friendly contacts, smiling, laughing, and the number of active and passive partners were assessed among 6–7 yr olds. Characteristics that describe an independent strategy used by girls showed strong dependence on gender. The 1st strategy of girls was to look at more children and laugh together with others, such behavior is rewarded by the decrease of received aggression. The 2nd strategy is to perform more demonstrations and avoidance; as a reward, more help is received. Aggressive interactions were more frequent compared to help in boy–boy, boy–girl, and girl–boy dyads. The ratio of aggression was higher for situations where boys were active aggressors. Correlation between friendly preferences and similarity in the general profile of social behavior revealed gender differences. (PsycINFO Database Record (c) 2016 APA, all rights reserved)