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The Descent of Sex: An Examination of Evolutionary Mating Strategies, Its Applications to The Human World, and The Implications on Gender Roles Andrea Pace 0560530 ASCI*4020 Sofie Lachapelle December 3, 2009 Introduction The Descent of Man, and Selection in Relation to Sex, Charles Darwin’s second significant book on evolutionary theory, presents the interesting concept of sexual selection. This concept outlines the differences found between males and females in regards to mating strategy and forces of selection. Sexual selection shows that the differences between the sexes have an impact on reproductive fitness through the action of obtaining mates (Freeman & Herron, 2007). When taken from a human perspective, mate selection is believed to be controlled by evolved, possibly subconscious mechanisms that have advanced in nature as a means of perpetuating the species (Urbaniak & Kilmann, 2006). When the book was published in 1871 it seemed to confirm the Victorian idea of men’s superiority to women. The book made use of its arguments to capitalize on society’s opinions on women, and their role in a man’s world. But when taken in a more modern context, the concepts provide a unifying theory of evolution that can be applied to the evolution of human mating including a more balanced perspective on male and female involvement. Recent studies done in the last decade or so have attempted to explain sexual selection and its role today in human mating. For example one can see parallels between female primates’ preference for males with good skin and coat condition, as well as males who display caring interactions with present infants, and the qualities one looks for in a significant other. These studies are able to support the idea of a contemporary theory of sexual selection. However, there are always other possible explanations for these results. Sexual behaviour can be affected by a variety of biological, societal, and cultural factors. Each of these factors has the possibility to affect both males and females in different ways (Fisher, 2009). This paper’s objective is to analyze sexual 2 selection theory, using evolutionary psychology, in order to assess sex and gender differences and the impact these theories has had on gender roles. This analysis will include a description of the theory of sexual selection and how it applies in the animal kingdom, a description of how the theory of sexual selection has been applied to the human kingdom, the impact of this evolutionary theory on gender roles, and alternative explanations for these mating strategies. This dissection of these theories and their applications will rely heavily on evolutionary psychology, sociobiology, social role theory, and feminist critique in order to create an all-encompassing perspective on the subject matter. Theory of Sexual Selection in the Animal Kingdom Underlying Principles of Sexual Selection As mentioned earlier, sexual selection states that the differences found between the sexes have an influence on reproductive fitness, specifically through obtaining mates (Freeman & Herron, 2007). Sexual selection theory predicts that sexual selection will act more strongly on the sex that is less reproductively invested in order to increase this species’ mating success (Freeman & Herron, 2007). The sex that is more strongly acted upon by sexual selection will be more competitive, and the sex that is weakly acted upon by sexual selection will be choosy (Freeman & Herron, 2007). The latter typically is found to be a female species, and the former is more often a male species. The competitive individual will compete for access to the opposite sex or for resources that are required by the opposite sex (Freeman & Herron, 2007). Females are often the choosier sex, being more discriminating when choosing a mate due to the fact that they 3 are more reproductively invested. This is because a females eggs are much more expensive to produce than the male sperm (Freeman & Herron, 2007). By being choosier, they will engage in a courtship with the opposite sex. This courtship will offer evidence of genetic quality of the male mate and also provide resources for the female and her offspring (Freeman & Herron, 2007). Since males can produce large quantities of sperm they are capable of fertilizing many females in rapid progression (Small, 1989). This ability predicts that males are expected to compete in order to achieve reproductive opportunities (Small, 1989). Competition can be described as being either intrasexual or intersexual. In the case of intrasexual competition, competition occurs between members of the same sex as a means of obtaining access to the opposite sex, or to resources. In nature, these are often presented as features used to combat with members of the same sex (Freeman & Herron, 2007). Intersexual competition is the evolution of behaviours used by one sex to attract members of the opposite sex that are choosy. This presents itself in nature as features or behaviours, such as beautiful and colourful plumage, that are used to convince members of the opposite sex to mate (Freeman & Herron, 2007). There are vast amounts of evidence to support these findings. One example is that female drosophila were found to favour male mates who performed the appropriate courtship behaviour (Small, 1989). Mate Preferences Between the Sexes Mate preferences between the sexes present themselves as varied. This is due to the fact that males and females have varied levels of reproductive investment involved in mating. As well, reproductive fitness is different depending on the sex of the species. Specific characteristics are selected for in nature because they enhance the mating 4 success of the particular species (Small, 1989). The other part of natural selection is choice, which typically falls into the hands of the female species. Mate choice consists of choosing individuals who display epigamic selection (adaptations that advance the union of gametes) or all-aesthetic selection (adaptations of displayed characteristics) (Small, 1989). Darwin stated that, “Males are eager to mate with just about any female” (Small, 1989). As such, in nature, males basic mission is to compete for fertile females (Small, 1989). Females, being the choosier sex, have a more discriminating approach to mate selection. Females display preferences for certain males. Female primates look for male mates who display good genes, high status, novelty, familiarity, access to resources, and qualities of parental care (Small, 1989). There are clear benefits for both the female and her offspring when she displays particular tastes for mates as well as discriminating mate selection. The power of female choice can be seen in the instance of runaway selection. Females’ specific preferences will cause them to always choose the same type of mates. This will result in male offspring similar to these male mates, and the propagation of selection for these desired traits (Small, 1989). It should be noted that there are instances in nature where males are the more invested sex (such as with seahorses, and Panamanian poison arrow frogs) (Vandermassen, 2004). In this case, forces of sexual selection are slightly different. Promiscuity in Nature Research often presents female species as monogamous and outlines the benefits of such a mating strategy. However, there are many pieces of evidence to show the benefits of having multiple mates. Females may mate with multiple males if the males in that area are often sterile, or as a means of maximizing the offspring’s genetic diversity 5 (Freeman & Herron, 2007). The “fertility back up hypothesis” states that females may require sperm from multiple males in order to assure conception (Blaffer-Hrdy, 1986). The “inferior cuckold hypothesis” states that females who have been paired with an inferior male will seek genetically superior males when conception is likely (BlafferHrdy, 1986). The “diverse paternity hypothesis” states that females who are confronted with unpredictable changes in the environment will produce clutches fathered by multiple males in order to diversify the offspring (Blaffer-Hrdy, 1986). There are many examples of this in nature. Female Savanna baboons initiate multiple and brief courtships (BlafferHrdy, 1986). Female chimpanzees often alternate between long-term courtships with one mate as well as communal mating with other mates in the area (Blaffer-Hrdy, 1986). The theory of sexual selection does indeed demonstrate that there are sex differences between mating strategies, mate preference, and mate choice. All of which are used as a method to increase reproductive fitness and success for the individual. Theory of Sexual Selection As It Applies in the Human Kingdom Underlying Principles of Human Mating Strategies The theory of sexual selection stated in terms of the animal kingdom is relevant and useful when examining human mating strategies as well. One sex, usually the male, will compete with other males to gain mating access to the other sex (Vandermassen, 2004). He will compete by using threats, combat, or by showing off (Vandermassen, 2004). Thus, male ornamentation and competition for females evolved so females can actively choose the strongest and best-ornamented males (Vandermassen, 2004). According to sociobiological theory the two key players in human mating are the 6 nurturing female (highly invested) and the competitive male (invests little) (Blaffer-Hrdy, 1986). The number of women he inseminates increases a man’s reproductive success, therefore it is expected that men desire higher numbers of sexual partners (Urbaniak & Kilmann, 2006). Therefore male’s reproductive success is limited by the number of fertile females he is able to mate with (Vandermassen, 2004). On the other hand, female’s reproductive success is limited by the time and energy that is required to raise offspring (Vandermassen, 2004). This explains why males are more eager to mate with many partners, and females are choosy when selecting a mate. Men attempt to increase their fitness by allowing less time to pass before seeking a sexual partner, having a greater desire for sexual variety, actively seeking short-term mating opportunities, and being more competitive (Vandermassen, 2004). Women attempt to increase their fitness by competing among other women for the features men find sexually attractive. They strive to attain beauty, youth, and to be more nurturing (Vandermassen, 2004). Females are able to maximize their fitness by being more discriminating (Archer, 1996). This strategy will be more likely to ensure a male mate with good genes, resources, and parental skills (Archer, 1996). Males are able to maximize their fitness by seeking many different mates (Archer, 1996). Males who are successful in obtaining a mate will enhance their reproductive success, resulting in these traits that contributed to the success as becoming more common in the species (Browne, 1998). Males can exert control over their attractiveness to females by regulating the amount of resources they have to offer to mates (Hill & Reeve, 2004). When two males compete for one female the winning male will always be the male who can continue to bid higher (offer more and more resources) than the other male (Hill & Reeve, 2004). The amount of resources required will increase 7 as the female’s quality increases and as the other male becomes more of a threat (Hill & Reeve, 2004). It is predicted that the higher quality male, with greater resources, will obtain the female (Hill & Reeve, 2004). When two females are bidding for one male, the winning female is the individual who, “when she makes her minimum profitable bid, would potentially yield higher offspring success for the male” (Hill & Reeve, 2004). These findings all suggest that men and women have evolved different adaptations that are used to guide their mating strategies (Eastwick & Finkel, 2008). Mate Preferences Between Sexes Mate preferences found in nature are very similar to those found among humans. Men seek out women who possess prominent cues that reveal their biological fitness, whereas women seek a single man who will be able to provide resources (Urbaniak & Kilmann, 2006). Biological fitness can be seen as being youthful and physically attractive, while a man who possesses resources is seen as being more likely to commit (Urbaniak & Kilmann, 2006). Men have shown preferences for women with child-like, neotenous facial features, because they promote reproductive success (Hopcroft, 2002). These features advertise a female’s youth and viability to a male mate, which will promote protective and supportive behaviours in males (Hopcroft, 2002). Females, being the more cautious sex, place greater importance on mates who have higher social status, ambition, and earning power that will all contribute to the increased fitness and survival of her offspring (Hazan & Diamond, 2000). In terms of physical attractiveness, both males and females look for these qualities. For females, this is a marker of good genes, which will also increase the offspring’s fitness (Koehler et al., 2002). Physical attractiveness consists of facial attractiveness and symmetry, height, body build, 8 attire/grooming, body language, and cues that signify dominance (Urbaniak & Kilmann, 2006). Both females and males show preferences for symmetrical bodies and faces. This demonstrates an adaptive mechanism of mate choice that signifies superior phenotypic and genotypic qualities in mate preferences (Koehler et al., 2002). Men look for features that are marks of reproductive potential, whereas women seek features that signify genetic fitness, resources, and protection (Archer, 1996). Research done involving online dating confirms these preferences. Men’s income predict the number of emails from women, and the physical attractiveness of a user’s photo can predict the number of emails a woman receives (Eastwick & Finkel, 2008). This standard evolutionary model of mate preferences shows evolved guidelines that act as forces upon males and females to desire certain qualities in a mate that will increase their own, and their offspring’s fitness (Hazan & Diamond, 2000). Short vs. Long-Term Mating Strategies Short-term mating constitutes partners engaging in sexual activity when there is a low probability of a relationship continuing (Wiederman & Dubois, 1998). Long-term mating is when there is an increased likelihood of a long lasting relationship (Wiederman & Dubois, 1998). In terms of short-term mating men have a higher interest in short-term mates than women do, men prefer a greater number of sexual partners over time than women, and men require less time to elapse before engaging in sexual activity than women (Schmitt et al., 2001). This is due to differences in maximizing fitness. Sex differences arise when comparing short-term and long-term mating. When considering short-term mating men place more emphasis on physical attractiveness, and prefer mates who are not looking for a long-term relationship (Wiederman & Dubois, 1998). In short- 9 term mating, women value financial resources, generosity, and cues to genetic fitness (Wiederman & Dubois, 1998). Women also prefer short-term mates who are seeking long-term relationships, allowing for the possibility of a future (Wiederman & Dubois, 1998). In long-term mating, men have higher standards for physical attractiveness in a long-term, female mate (Wiederman & Dubois, 1998). In long-term mating for women, the emphasis of importance on available resources becomes more significant of a factor (Eastwick & Finkel, 2008). Benefits of Promiscuity (Short-Term Mating) In Human Mating So-called promiscuous males benefit evolutionary by increasing their reproductive fitness (Schmitt et al. 2001). There are many explanations as to why promiscuity in females is beneficial. Engaging in short-term mating is advantageous because women can gain immediate material resources (Wiederman & Dubois, 1998). Women may seek superior short-term mates as a back up to their current mates (Schmitt et al., 2001). In areas where the number of viable long-term partners is low, short-term mating is functional for women (Schmitt et al., 2001). Many women find a short-term mating encounter to be just as positive as a man would (Campbell, 2008). As well, shortterm mating could act as a “test run” for a potential long-term mate (Campbell, 2008). The sex differences found in human mating strategies and preferences are effectively explained by the standard evolutionary sexual selection theory, and account for benefits to reproductive fitness. These explanations relate closely to the theories underlying sexual selection in the animal kingdom. Impact of Sexual Selection Evolutionary Theory on Gender Roles 10 Original Bias in Darwin’s Theory Darwin’s original evolutionary theories fit well with the social beliefs of the 19th century. The animals he described in his theories were, “cast into roles from a Victorian script” (Hubbard, 1979). His account of human nature presented the active male and the passive female (Hubbard, 1979). This pattern of male dominance and female resistance (or discriminating nature) has led to the development of patriarchal arrangements in human society (Vandermassen, 2004). This evolution of patriarchy has arisen due to the conflict between reproductive interests (Archer, 1996). Men have gained the advantage over women due to size and strength, but also by overcoming female choice (Archer, 1996). The theory of sexual selection, despite its supporting evidence, has allowed for the evolution of male exploitation of the reproductive efforts of females (Vandermassen, 2004). In presenting the female as “coy” and “passive”, the female’s involvement is not value neutral (Vandermassen, 2004). Darwin’s original presentation of theories often seems to be suggesting that a male’s secondary sex characteristics are more important than a female’s (Vandermassen, 2004). Today, due to increased female involvement in the field of animal behaviour and evolution, the facts are presented more logically and more inclusive. Due to the societal climate during the original publication of these theories, some gender biases can be found in the literature. However, especially in today’s society, these gender biases are not taught or the emphasis of the arguments. Division of Labour Boys are taught to be aggressive, tough, willing to fight, and to be self-reliant. In contrast girls are taught to be industrious, responsible, and obedient (Archer, 1996). 11 These tendencies in boys are not only enforced by society but are shown to be a general tendency in mammalian species. This difference in enforced traits can have significant implications at the workplace (Browne, 1998). Status in society was shown to have reproductive payoffs for men (Browne, 1998). This has left men to be more interested in reaching high status in a hierarchy than women and more likely to utilize aggressive behaviour to reach the top of this hierarchy (Browne, 1998). To reach the top of a workplace hierarchy one must display competitiveness, willingness to take risks, and room for making a large investment (Browne, 1998). Men, being less invested in child rearing and more determined to gain status and resources, disproportionately occupy these high status positions in occupational hierarchies (Browne, 1998). As well, in patriarchal systems men are provided the power and status to achieve the benefits of this division of labour (Eastwick et al., 2006). Young women have low task related selfesteem when they compare themselves to men. This may have evolved because such a trait advertised youth and controllability, both attractive characteristics to a male mate (Hopcroft, 2002). This tendency of women belittling their contributions and capabilities may help to explain the stereotype of women as weak and inferior, and men as strong and superior (Hopcroft, 2002). These tendencies may result in women not pursuing additional training and education in order to develop their abilities and skills (Hopcroft, 2002). This will then act to exclude women from the benefits of this division of labour (Hopcroft, 2002). Benevolent and Hostile Sexism Paternalistic attitudes (restriction of freedom, protecting and cherishing women etc) have evolutionary been considered an attractive quality in a mate (Hopcroft, 2002). If 12 women enforce these attitudes they will be met with benevolent discrimination. This is the idealizing and rewarding of women who remain in their conventional, stereotyped roles (Eastwick et al., 2006). In contrast, hostile sexism is when women who take on traditional male roles (aggressiveness) are demeaned or punished (Eastwick et al., 2006). This traditional, idealized view of women that causes both benevolent and hostile sexism is founded by evolutionary sex differences. Sexual Double Standards Young girls are taught to be sexually restrained (Archer, 1996). Unsurprisingly, women with more elaborate sexual histories are met with derogatory evaluations (Jonason et al., 2009). However, men with many sexual partners are viewed as having more prestige than those who do not (Jonason et al., 2009). Herein lies society’s sexual double standard. According to sexual selection theory men should be more approving of casual sex and should have larger numbers of mates in order to increase reproductive fitness (Oliver & Hyde, 1993). Sexual success among males is based on access to a limited resource: women’s sexuality (Jonason et al., 2009). These views have lead to the existence of the double standard of society’s easygoing attitudes towards male promiscuity and conversely intolerant opinions of female promiscuity. Alternative Explanations Alternative perspectives other than evolutionary sexual selection can explain the mating strategies and preferences stated throughout the literature. By including these alternatives explanations one gains a more thorough perspective on human mating. Attachment theories state that both males and females seek qualities that make a good 13 attachment figure (kindness, warmth, and competence) (Hazan & Diamond, 2000). Unlike sexual strategies theories, these qualities do not vary as a function of sex (Hazan & Diamond, 2000). According to social role theory, an individual can adopt sex differences in social behaviour through the learning of sex typed skills and beliefs, and through gender role expectancies (Archer, 1996). Cultural traditions can enforce aggressiveness and dominance as well (Archer, 1996). It is also a possibility that sex differences in sexual behaviour are due to the individuals reporting these differences rather than actual behavioural differences (Fisher, 2009). These biological differences may exist but it is possible that they are exaggerated due to the impact of societal and cultural beliefs (Fisher, 2009). Participants of these studies that are providing evidence for sexual strategy theories may state specific preferences and strategies as more favourable due to the preexisting assumptions of what society would expect of them (Eastwick & Finkel, 2008). As well, the focus of these arguments is that sexual activity is based on reproduction and creation. There is the alternative explanation involving romance, love, and realistic, loyal commitment (Vine, 2000). Finally, there is the classic psychological perspective that states individuals seek a long-term partner who is similar to himself or herself in looks to avoid being rejected or dissatisfied (Schneider et al., 2005). These arguments present findings parallel with those found throughout the evolutionary literature, however their modes of inquiry and exploration are different. This allows for a holistic view of human mating strategies. Conclusion 14 It is clear that there are sex and gender differences within the theory of sexual selection. Evolutionary perspective maintains that there are differences in selective forces, mating strategies, and mate preferences found between the male and female sex. These differences are what allow for specific adaptations and strategies that are meant to optimize an individual’s mating and reproductive success. Evolutionary speaking, this is the main goal of human mating: reproduction and maximized fitness. Just like the rest of the natural world, humans are not excused from the laws of evolution. To deny these differences does not strengthen any argument due to the fact that there is mounting evidence to support the theories. Unfortunately, it is also clear that these theories that emphasize sex differences in order to explain sexual selection have severe implications for society, gender roles, and sexual discrimination. The facts and explanations supporting these evolutionary theories are not directly troublesome. It is during the process of interpretation where the emphasis and focus of the science becomes lost in translation. This problem of negative interpretation is what causes significant implications on gender roles. Despite these negative consequences of evolutionary theory, it appears that as society evolves, radical changes are being made to combat these expected roles and to enforce new ways of thinking. In order to better understand human nature, behaviour, and its mechanisms all possible perspective must be taken into account. It is only then that society can evolve, embrace differences between the sexes, and enhance current theories. 15 References 1. Archer, J. 1996. Sex Differences in Social Behavior. Are the Social Role and Evolutionary Explanations Compatible? American Psychologist 51: 909 – 917. 2. Blaffer-Hrdy, S. 1986. “Empathy, Polyandry, and the Myth of the Coy Female”. 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