INDEPENDENT DIFFERENTIATION OF SEXUAL AND SOCIAL TRAITS

In the process of development in mammals and birds, an individual beco mes either male or female. The dogma of sexual differentiation explain s this development in terms of gonadal secretions, which direct the gr owth of an organism along masculine or feminine lines. However, this t ype of bimodality is not found in all traits that are displayed in rep roductive contexts. For example, aggressive behaviors displayed during the breeding season can be expressed by both males and females. Furth ermore, this reproductive aggression is highly variable between indivi duals, regardless of sex. The development of variable traits like repr oductive aggression is therefore likely to be influenced by factors in addition to gonadal secretions. We propose that social traits associa ted with reproduction can differentiate along pathways that are distin ct from the developmental pathways of primary sexual traits. (C) 1996 Academic Press.