ABSTRACT
The comparative perspective offers insight into the rules, principles, or generalizations that govern the structure and function of the brain and illuminates the roots from which they emerged. Behavior-genetic analyses such as screening for mutants or selective breeding reveal the potential for the brain to change in response to artificial selection, not how the brain responds to the selection pressures present in nature. Pseudosexual behavior in parthenogenetic whiptails is related to the ovarian cycle. In the sexual ancestral species, sexual activity in males is dependent on testicular androgen, and administration of exogenous androgen stimulates male-like pseudosexual behavior in the unisexual whiptail. During the last decade the focus of the laboratory has been on individual variation in the capacity of progesterone (P) to induce male-typical behavior, the evolution of underlying mechanisms, and structure-function relationships in brain and behavior. The chapter focuses on sexual dimorphisms in the reptilian brain, and in particular in the whiptail lizard.
