BEHAVIORAL AND BRAIN SCIENCES (2000) 23, 573–644 Printed in the United States of America The evolution of human mating: Trade-offs and strategic pluralism Steven W. Gangestad Department of Psychology, University of New Mexico, Albuquerque, NM 87131 [email protected] Jeffry A. Simpson Department of Psychology, Texas A&M University, College Station, TX 77843 [email protected]. Abstract: During human evolutionary history, there were “trade-offs” between expending time and energy on child-rearing and mating, so both men and women evolved conditional mating strategies guided by cues signaling the circumstances. Many short-term matings might be successful for some men; others might try to find and keep a single mate, investing their effort in rearing her offspring. Recent evidence suggests that men with features signaling genetic benefits to offspring should be preferred by women as short-term mates, but there are trade-offs between a mate’s genetic fitness and his willingness to help in child-rearing. It is these circumstances and the cues that signal them that underlie the variation in short- and long-term mating strategies between and within the sexes. Keywords: conditional strategies; evolutionary psychology; fluctuating asymmetry; mating; reproductive strategies; sexual selection Research on interpersonal relationships, especially roman- attributes (e.g., physical attractiveness) tend to assume tic ones, has increased markedly in the last three decades greater importance in mating relationships than in other (see Berscheid & Reis 1998) across a variety of fields, in- types of relationships (Buss 1989; Gangestad & Buss 1993 cluding social psychology, anthropology, ethology, sociol- [see also Kenrick & Keefe: “Age Preferences in Mates Re- ogy, developmental psychology, and personology (Ber- flect Sex Differences in Human Reproductive Strategies” scheid 1994). Unfortunately, these diverse perspectives BBS 15(1) 1992]). Specific facial and body features predict have not coalesced into larger, more integrative theories of the attractiveness of mates in nearly all cultures (Cunning- how and why relationships function the way they do. ham et al. 1990; Jones & Hill 1993; Perrett et al. 1994). Evolutionary principles can integrate the findings on in- Marriage is culturally universal (Daly & Wilson 1988). This terpersonal relationships, especially concerning mating and parental behavior. In the evolutionary approach one tries to understand human psychological design – the nature, or- ganization, and operation of domain-specific psychological mechanisms – by identifying plausible constraints from Steven W. Gangestad is Professor of Psychology and selection pressures during evolutionary history (see Buss Regents’ Lecturer at the University of New Mexico. He 1995). Human behavior is highly flexible and environmen- received his Ph.D. from the University of Minnesota in tally responsive but “[psychological] designs that produce 1986. In the past decade, his major research interests ‘plasticity’ can be retained by selection only if they have fea- have been in evolutionary psychology, with particular emphasis on human sexual selection, the evolution of tures that guide behavior into the infinitesimally small re- mating strategies, the maintenance of genetic variation gions of relatively successful performance with sufficient in populations, and the evolutionary-genetic underpin- frequency” (Tooby & Cosmides 1992, p. 101). To under- nings of neurodevelopmental variation. stand behavioral flexibility (i.e., the ability to adjust adap- tively to specific environmental circumstances), especially Jeffry A. Simpson, Professor of Psychology at Texas in the form of cultural variation, one must understand the A&M University, received his Ph.D. from the Univer- psychological architecture that guides social interactions. sity of Minnesota in 1986. He has written over 70 pub- Romantic relationships have several unique qualities lications in social/personality psychology. Most of his research focuses on interpersonal relationships, partic- that distinguish them from other types of relationships. ularly mating, attachment, and relationship mainte- Romantic love, for example, differs from other forms of nance processes. He has served on the Social Psychol- love (Hendrick & Hendrick 1986). Sexual jealousy has fea- ogy grant panel at the National Science Foundation, tures and consequences that differ from other types of jeal- serves on the editorial boards of several journals, and ousy (Daly & Wilson 1988; Daly et al. 1983). Specialized currently is the editor of the journal Personal Relation- verbal and nonverbal courtship rituals are observed in vir- ships. tually all cultures (Eibl-Eibesfeldt 1989). Certain personal © 2000 Cambridge University Press 0140-525X/00 $12.50 573 Gangestad & Simpson: Evolution and human mating all suggests that a specialized psychological architecture 1. Basic evolutionary concepts may underlie and guide romantic interactions. This would make sense considering the importance of mating, repro- 1.1. Sexual selection duction, and parenting throughout evolutionary history. Sexual selection refers to discrepancies in reproduction The fact that the ties between mating and reproduction rates among individuals resulting from the various “advan- can now be severed by contraception does not imply that tages” in mating, independent of advantages resulting from evolved psychological mechanisms no longer influence hu- differential survival. Evolutionary biologists have tradition- man mating (see Symons 1987; 1992; Thornhill 1991; ally studied the effects of sexual selection on two kinds of Tooby & Cosmides 1992). [See also BBS multiple book re- adaptations: (a) intrasexual competitive abilities, and (b) view of Symons’s The Evolution of Human Sexuality, BBS specialized signals that appeal to members of the opposite 2, 1980.] sex (Andersson 1994). In many species, the number of dif- Evolutionary theories of human mating have been heav- ferent mates that one sex can obtain is related directly and ily influenced by research on mating in other animals (see strongly to reproductive success, whereas this is less true of Campbell et al. 1999). These theories – especially Trivers’s the other sex. In most mammals, the former sex is male, and (1972) theory of sexual selection and parental investment – the latter, female (whose reproductive output is limited by clarified the major (and slightly different) barriers that internal gestation and lactation). Thus, in most mammals, males and females in most species must surmount to in- females are a limited reproductive resource for males, who crease their inclusive fitness. Trivers’s work launched the compete to attract mates. Given this disparity, sexual selec- strong theoretical and empirical focus on sex differences in tion pressures should have acted more strongly on the male human mating strategies, most of which has tried to explain intrasexual competitive abilities and the specialized signals why women, in comparison with men, tend to be more dis- appealing to female preferences than vice versa (see Cronin criminating when choosing mates and more “restricted” in 1991; Trivers 1972). Empirical evidence supports these their sexual behavior. Recently, Buss and Schmitt (1993) predictions in many different species (see Trivers 1985). have applied and extended many of Trivers’s ideas in devel- Theories about the signals or cues that females prefer in oping their Sexual Strategies Theory (SST). The focus on mates have focused on two types: (a) attributes that tend to sex differences in human mating has been criticized, how- signal qualities of a “good parent” (or a “good provider”), ever, for not explaining why there is more variation in mat- and (b) attributes suggesting that an individual may have ing-related behaviors within sexes than between (see “good genes” (Cronin 1991; Gangestad 1993; Miller 1998). Gangestad & Simpson 1990) and for not considering how Theories of good parenting have been fairly uncontrover- women’s control of resources may have influenced the mat- sial. Those involving good genes, on the other hand, have ing strategies of both sexes (see Gowaty 1992a; 1992b; Hrdy been debated extensively (see sect. 3). Consequently, most 1997). applications of sexual selection to human mating have not In this target article, we show how evolutionary princi- seriously considered good-gene sexual selection. Recently, ples can extend and deepen our understanding of human however, theoretical and empirical research has indicated mating, and how and why both sexes display both short- and that both good-parenting and good-gene selection could long-term mating tactics in certain contexts. SST (Buss & have operated on many species (Kirkpatrick 1996; Møller Schmitt 1993) tries to explain why men tend to adopt short- 1994b), particularly those in which males provide substan- term mating tactics more often than women. SST also em- tial parental care (as is true of humans). In what follows, we phasizes that both men and women have evolved mixed will argue that these selectional processes are likely to have strategies involving both long- and short-term matings. Af- produced differential mating tactics within each sex. ter reviewing SST, we will argue that selection produced Natural selection also has important implications for hu- mixed strategies that depend on environmental circum- man mating. In many species, parental care by males might stances and their cues. Men and women accordingly shift have evolved