Sexual Orientation: What Have We Learned from Primate Research?
Because of the ideas of Alfred Russel Wallace and Charles Darwin regarding the continuity of species, humans look to nonhuman species to understand the biological basis of human sexual behavior. Animal models were used initially to address fundamental questions of how. Research focused on reproductive physiology, and the value of these animal models in biomedical research has been firmly established ( Beach 1979a; Gooren 1990). Subsequently, the focus of research shifted to questions of why and there has been a disproportionate emphasis on explaining the causes and functions of nonreproductive sexual behavior (e.g., homosexual behavior) and associated phenomena such as sexual orientation.
This focus has been attributed to teleology inherent in the biomedical approach to sexual behavior wherein reproductive sexual behavior is viewed as a "natural" process shaped by a purpose and directed toward an end ( Gooren 1990). Cause and function are simultaneously explained as procreation and then dismissed. In contrast, nonreproductive sexual behavior precludes procreation and is considered "unnatural" and thus demands explanation ( Gooren 1990). Unfortunately, this view confuses causation and function. Whether or not the function of reproductive sexual behavior is the contribution of genes to future generations, the immediate causes and developmental influences also warrant investigation. Moreover, one cannot expect to understand nonreproductive sexual behavior fully until there is a sufficient understanding of the causal mechanisms for reproductive sexual behavior ( Beach 1979a).