THEORETICAL FOUNDATIONS OF HUMAN SEXUALITY

The aim of this review is to put core features of human sexuality in an evolutionary light. Toward that end, I address five topics concerning the evolution of human sexuality. First, I address theoretical foundations, including recent critiques and developments. While much traces back to Darwin and his view of sexual selection, more recent work helps refine the theoretical bases to sex differences and life history allocations to mating effort. Second, I consider central models attempting to specify the phylogenetic details regarding how hominin sexuality might have changed, with most of those models honing in on transitions from a possible chimpanzee-like ancestor to the slightly polygynous and long-term bonded sociosexual partnerships observed among most recently studied hunter-gatherers. Third, I address recent genetic and physiological data contributing to a refined understanding of human sexuality. As examples, the availability of rapidly increasing genomic information aids comparative approaches to discern signals of selection in sexuality-related phenotypes, and neuroendocrine studies of human responses to sexual stimuli provide insight into homologous and derived mechanisms. Fourth, I consider some of the most recent, large, and rigorous studies of human sexuality. These provide insights into sexual behavior across other national samples and on the Internet. Fifth, I discuss the relevance of a life course perspective to understanding the evolution of human sexuality. Most research on the evolution of human sexuality focuses on young adults. Yet humans are sexual beings from gestation to death, albeit in different ways across the life course, and in ways that can be theoretically couched within life history theory. Am J Phys Anthropol 57:94–118, 2013. VC 2013 Wiley Periodicals, Inc. The aim of this review is to put core features of human sexuality in an integrative, evolutionary light. Given the central importance of sexuality to the evolutionary imperative—reproductive success—there is strong theoretical impetus for understanding how evolution has shaped human sexuality in the past, and for how the influence of past selective forces continue to manifest in the present. For biological anthropologists, interdisciplinary social and biomedical scientists, and even wider audiences, questions about human sexuality can be among the most compelling and meaningful, another reason to try informing answers to fundamental questions of human sexuality with the most scientifically supported and current views. An understanding of human sexuality is central to topics as diverse as predicting the dynamics of a sexually transmitted infection (STI) outbreak to the reasons why people pour so much of their time and resources into mating effort. Human sexuality, as much as any other topical focus within biological anthropology, warrants ongoing evolutionary scrutiny. For several reasons, this is arguably an opportune time for providing a current overview of the evolution of human sexuality. For one, many of the foundational theoretical and empirical touchstones in biological anthropology that focus on the evolution of human sexuality are dated. Darwin’s (1871) seminal contributions continue to shape our thinking regarding sexual selection, sex differences, and evolutionary models of human mating. So too do important contributions from the 1970s and 1980s such as Symons (1979) Evolution of Human Sexuality and Hrdy’s (1981) The Woman that Never Evolved. Of more recent and prominent works focused on the evolution of human sexuality, however, many draw heavily from evolutionary psychology, such as David Buss’ (2003) The Evolution of Desire. The field can benefit from a current overview of the evolution of human sexuality that integrates many of the disparate strands of work and that helps orient ongoing scholarship. If the field does not do this, others will fill that gap, leaving open the potential for best-selling but theoretically and empirically distorted works such as Ryan and Jetha’s (2010) Sex at Dawn to shape how people think human sexuality evolved. A second reason for a review is new theoretical and empirical work on the evolution of human sexuality. The theoretical foundations to sex differences in mating effort, for example, can also reflect demographic factors that had been less appreciated in previous theoretical formulations. New data from neuroimaging, hormonal studies, and genetics and genomics contribute to an enriched understanding of the mechanisms of human sexual behavior. The availability of more recent sex survey data drawing upon large, international, and even Internet-based content helps provide new insights into the patterning of human mating and interest in sexual stimuli. How these new lines of evidence fit with other lines of evidence and evolutionary theory is worthy of investigation. New theory and data could potentially transform, or slightly modify, or even affirm earlier perspectives regarding the evolutionary foundations of *Correspondence to: Peter B. Gray; Department of Anthropology, University of Nevada, Las Vegas, 4505 Maryland Parkway, Box 455003, Las Vegas, NV 89154-5003. E-mail: peter.gray@unlv.edu DOI: 10.1002/ajpa.22394 Published online in Wiley Online Library (wileyonlinelibrary.com). 2013 WILEY PERIODICALS, INC. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 57:94–118 (2013)