The Evolution of Human Sexuality: Humans are sexual creatures. Human preoccupation with sex and sexuality makes sense from an evolutionary perspective. In par- ticular, Evolutionary Psychology EP has proven to be a valuable heu- ristic approach for generating and testing hypotheses about human sexuality.
The main theme of this volume is the evolution of human sex- uality, or evolved human sexual psychologies. A second theme is the identification of implicit conceptual assumptions about sexual attraction and the operational definition of key terms in order to promote greater integrity of conceptual models.
Evolution, psychology, human sexual attraction, as- sumptions Michael R. The author thanks Frank Muscarella for his helpful comments on an earlier version of this manuscript. Handbook of the Evolution of Human Sexuality ed: Kauth The Haworth Press, Inc. A clear example of how sexual human culture is can be found in a quick survey of popular Western culture. Sexy images of young, beautiful, and se- ductively clad women and men are employed in advertisements for any number of products automobiles, beverages, couture, deodorant, erec- tile enhancing drugs, floor cleaners, etc.
The fact that sexy images are used so frequently for so many products is evi- dence that the strategy works. Acquiring the product may then evoke in the consumer a feeling of sexiness, or the possibility of sexual conquest and sexual fulfillment that is alluded to by the advertising images. Sexual behavior and sexuality are central themes of popular Western entertainments: As subject matter, sexuality seems to be a fathomless well; similar stories of love and loss have been told and re-told for thousands of years.
In Western culture, sexual be- havior and sexuality are frequent topics of discourse that on any given day may include speculation about possible sexual activity, relation- ships, condoms, masturbation, orgasm, abstinence, pregnancy, abor- tion, homosexuality, sexual infidelities, or sexual jealousy. In addition to talking frequently about it, many people experience sexual arousal most days or engage in some form of sexual activity—flirtations, sexual fantasies, masturbation, or intercourse.
Although men and women are sexually aroused by different sexual stimuli and prefer different types and frequencies of sexual behaviors, most people attend and respond to sexual stimuli in the environment Chivers, Why are humans so consumed with sexuality? No less provocative but perhaps more tangible are scientific explanations of hu- man nature that are based on established theory and systematic observa- tion.
Scientific explanations have the advantage of being observable by others and generating testable predictions. That is, evolutionary theory helps to explain how particular traits evolved within a species and whether a trait is adaptive or functional Symons, Adaptive traits adaptations evolved to solve problems related to survival and reproduction in the ancestral environment of the organism.
Reproductive success, not sur- vival, is the ultimate function of a trait: Even traits that confer very small selective advantages can, over many generations, enhance the repro- ductive success of organisms with the favored trait, until eventually the trait spreads throughout the population Haldane, Common hu- man features such as upright posture, walking, verbal language, and in- terest in sexual stimuli, for example, can be explained by natural selection theory as adaptations that enhanced the reproductive fitness of our early ancestors and so spread through the population.
Other fea- tures, such as physical differences between the sexes, can be explained by sexual selection theory as traits associated with reproductive fitness and favored by one but not the other sex. Sexual selection theory also helps to explain sex differences in sexual psychologies that result in dif- ferential mating behaviors.
By incorporating both natural and sexual se- lection theories, Evolutionary Psychology EP has emerged as a productive approach for generating hypotheses about human sexual psychologies and testing them. Anthropologist Donald Brown has claimed that human so- cieties share similar ways of thinking, feeling, and behaving, which are likely a result of our evolutionary history as a species.
A universal human nature, or evolved psychology, makes it possible for humans to communicate with and understand alien human cultures Pinker, Thus, we should expect that human nature is highly attuned to sexuality and sexual communication. From an evolutionary perspective, human preoccupation with sexu- ality makes perfect sense Taylor, By contrast, early humans with only a modest or infrequent interest in sex would rapidly have been out-repro- duced by sex-focused members of the species.
Contemporary humans are the product of generations of reproductively successful ancestors who were preoccupied with sexuality. However, few humans today live exclusively in the natural environment under conditions similar to those experienced by our ancestors. As well, modern life presents challenges and opportunities that early humans never faced and could not have imagined.
Nevertheless, knowledge of human evolution can help to ex- plain, for example, why people today respond favorably to certain sex- ual images readily exploited by advertisers , why people fall in love, why people are attracted to particular sexual features, why people expe- rience sexual jealousy, why males feel protective of their mate and readily fight with other males, why partners sometimes cheat on each other, and why females strive to appear sexy but are choosey in select- ing a mate.
Evolutionary theory can also help to explain why some sex- ual behaviors are taboo and perceived as disgusting, and possibly why many people experience varied sexual attractions. For many, the edited volume, The Adapted Mind,is the bible of EP, although the edited and equally scholarly Handbook of Evolutionary Psychology is well on its way to becoming a classic text.
Yet the contributors of The Adapted Mind, although focused on psy- chological mechanisms of human social behavior, largely ignore sexual selection theory and give little attention to human sexual psy- chologies. The mammoth Handbook, while incorporating both natural and sexual selection theories and focusing more on human sexuality, is written for the advanced evolutionist. The Mating Mind, amoreac- cessible text, is written for a general audience. This volume is written for sexual scientists, scholars, and students who wish to understand adult-adult human sexual attraction and behavior and are relatively new to recent evolutionary theories.
Thus, the principal theme of this volume is the evolution of human sexuality. Contributors discuss the evolutionary history of human sexu- ality, including linkages to non-human primate sexual behaviors and the emergence of human sexual culture. Contributors also present current findings from EP studies on consensual adult human sexual behaviors, including evolved male and female mating strategies, mate preferences, and sexual psychologies.
The elusive role of sexual attraction and sex- ual orientation is a recurring theme. Sexual attraction is more difficult than sexual behavior to measure, but more comprehensive. Elucidating sexual attraction approaches the problem of understanding sexual ori- entation. Several contributors note the prevalence of varied nonexclu- sive sexual attractions in human societies, and four contributors discuss theories of the development and function of same-sex sexual at- traction.
This volume does not attempt to explain all aspects of human sexual- ity. The contributors and I hope that the ideas expressed here will stimu- late scholars and researchers to investigate other areas of human sexuality from an evolutionary perspective. Introduction 5 There is now a considerable literature on the evolution of human sex- ual behavior, much of it generated recently by evolutionary psycholo- gists. Confirming evidence has led to some findings e.
Yet there is still much to know, and there are many areas where scientific opinions differ. Good scientists sometimes disagree, and differences of opinion are likely to be found at the fuzzy edges of phenomena. Human sexuality has a lot of fuzzy edges. For me, the scientific process is most interesting when scientists struggle with how to make sense of something. That struggle is evident in this volume. The contributors were selected to present good evolu- tionary science, rather than present a range of viewpoints.
However, as they try to bring the fuzzy edges of human sexuality into better focus, several contributors have proposed different interpretations of similar data and make strong arguments for their case. This volume begins with a depiction of the historical and social con- text of evolutionary theory. Cultural context shapes how both scientists and nonscientists view evolution and human sexuality.
Sprinkled throughout the history, I introduce key concepts of evolution- ary theory that are employed extensively in later texts. I also identify and discuss fundamental assumptions of evolutionary theory and EP.
Christian evangelicals have long opposed evolu- tion and opposed openness about sexuality and have often linked the two, attributing a host of evils—moral decline in the United States, sex- ual promiscuity, abortion, and tolerance of homosexuality—in large part to the teaching of evolution and sex education in public schools.
Next, archaeologist Timothy Taylor provides an ancient cultural con- text to this project, with an overview of hominin evolution and the birth of human sexual culture. Taylor then challenges several assumptions about premodern human sexuality, asserting that contraception was more widely available than has been traditionally thought and that exclusive heterosexuality was not the dominant form of sexual behavior in ancient human cultures, citing evidence of varied sexual practices and of ritual condemnation of aberrant sexual practices.
He hypothesizes that constellations of human groups engaged in early social practices that then shaped human sexuality and behavior and in turn influenced the emerging culture. It is difficult to imagine sexual behavior without sexual pleasure. Garza-Mercer ar- gues that pleasure associated with conceptive behavior ensures that such behavior will occur with sufficient frequency.
Further, the asso- ciation of pleasure with nonreproductive sexual behaviors e. Thus, a heightened capacity for sexual pleasure may be an evolved human trait.
More generally, Garza-Mercer adds, the experience of pleasure and pain may drive human behavior. The next two texts describe evolved human reproductive strategies and mate preferences. Differential reproductive costs have led males and females to develop different, sometimes competing, mating strategies and specific mate preferences. For example, because women have a large reproduc- tive investment e. On the other hand, because men have a lesser reproductive investment e. However, for many reasons, men often pursue long-term mateships to maximize their repro- Introduction 7 ductive success, and women sometimes seek out short-term sexual part- ners.
Sefeck, Brumbach, Vasquez, and Miller make the important point that sexual decision-making is context-dependent: Mating patterns can be shown to vary with the harshness of the natural environment and availability of material and nutritional resources. The influence of context—natural, so- cial, behavioral, economic, and political context—on mate preferences and mating patterns is often ignored by critics who portray evolutionary explanations as rigid and deterministic.
Sefcek and colleagues also describe how humans, like all sexual or- ganisms, have developed sexual signals to advertise their quality e. Human fitness signals include physical features, as well as social status, fashion, networks of friends, and material wealth. He finds that sex differences in sociosexual behavior are robust and culturally universal, supporting pa- rental investment theory and sexual strategies theory.
From this large dataset, Schmitt concludes that men are consistent in their sexual attitudes re- gardless of sexual orientation or where they live. However, among men, sexual behaviors differed by sexual orientation, probably due to the fact that gay men have sex with men who may share similar attitudes about sexuality. Among women, however, bisexuals differed significantly from both heterosexual women and lesbians in sexual attitudes and be- haviors.
The next four texts address the evolution of same-sex sexual attrac- tion and behavior. Some same-sex sexual behavior is a common feature of human populations. According to contemporary surveys, even exclu- sive same-sex sexual behavior occurs above the level of a random muta- tion, and exclusive same-sex sexual attraction is also well-documented in human history.
Here, four contributors take very different approaches to explain same-sex sexual attraction. Each draws somewhat different conclusions about the adaptive function of same-sex sexual attraction. Primatologist Paul Vasey employs functional and phylogenetic per- spectives to frame his extensive observations of female Japanese ma- caques and female-female sexual encounters. Female macaques, unlike other primates besides humans, sometimes prefer female sexual part- ners over male partners for significant periods of time.
Vasey provides convincing evidence that female macaques are indeed selecting female sexual partners for sexual encounters, perhaps solely for sexual plea- sure.
He concludes that same-sex sexual behavior among female Japa- nese macaques serves no reproductive function and is a by-product of female-male mounting an adaptation.