the diversity of life in the natural world, the mechanisms by which this within- and between-species diversity arose, and how and why species will continue to change.Read more at location 712
has to give up 50% of one’s genes to reproduceRead more at location 719
benefits include the cross-generational elimination of deleterious mutations, the ability to adapt to changing ecologies, niche seeking in socially competitive environments, and an ever changing system of defense against rapidly evolving parasites (Apanius et al., 1997; Dawkins & Krebs, 1979; W. D. Hamilton & Zuk, 1982).Read more at location 722
With the evolution of sexual reproduction came the evolution of sex differences,Read more at location 726
Across species, female choice tends to focus on those characteristics that are an honest—not easily faked—signal of male quality (Zahavi, 1975).Read more at location 1342
The expression of these characteristics is typically costly for the male.Read more at location 1345
only the fit males can develop the quality of secondary sexual characteristic necessary to attract mates and therefore sire offspring (e.g., Møller, 1994a).Read more at location 1346
Male–male competition typically has the same effect as female choice; a few males sire most of the next generation, and most males leave no offspring.Read more at location 1347
males compete on those dimensions that females use in their choice of mating partners, as illustrated by the bower-building activities of male bowerbirds (Borgia, 1995a).Read more at location 1350
The traditional focus on female choice and male–male competition does not belie their counterparts, that is, male choice and female–female competition. These aspects of sexual selection have now been observed across a wide variety of species (e.g., Berglund et al., 1997)Read more at location 1352
When males parent, they become an important resource over which females compete, in the same way that males compete over mates in species in which females provide most of the parental effort.Read more at location 1357
Whether sexual reproduction centers on female choice, male–male competition, male choice, female–female competition, or some combination, the result is the evolution of sex differences for those traits that facilitate choice and competition.Read more at location 1359
the function of growth and developmental activity is to accumulate reproductive potential, that is, to build the type of body and acquire the types of behavioral and cognitive competencies needed to survive to reproductive age and then to successfully reproduce (R. D. Alexander, 1987).Read more at location 2092
Plasticity in the expression of life history traits represents the evolved potential to physically, behaviorally, and cognitively accommodate, within norms of reaction constraints, variation in these conditions.Read more at location 2101
The male–male competition of northern elephant seals results in conditions that favor a longer developmental period during which males gain the weight and physical size needed to compete for mates (Le Boeuf & Reiter, 1988). Female northern elephant seals do not compete for access to mates, and there is no advantage to delaying reproductive maturation;Read more at location 2104
For slow maturing species, developmental activities include play activities that have no immediate function and mimic to some degree the activities of adulthood (Burghardt, 2005).Read more at location 2110
Sex differences in play activities are equally informative, as they have been documented across a wide range of species and often track sex differences in adult reproductive strategy (Power, 2000).Read more at location 2114
When both sexes compete physically, both males and females engage in rough-and-tumble play.Read more at location 2116
Hormones do not deterministically cause sex differences but rather interact with genetic sex, developmental history, and current conditions to bias males and females to behave in ways that often differ (Wingfield et al., 1990). In fact, sex hormones appear to moderate the expression of many, if not all, of the sex differences described in this chapterRead more at location 2126
In most nonmonogamous species, male–male competition is a very conspicuous feature of these dynamics, and as such, it is not surprising that this competition is one of the better studied features of primate social behavior (Smuts, 1987).Read more at location 2787
The prototypical result is larger and more aggressive males than females (Plavcan et al., 1995).Read more at location 2790
Whether they involve one-on-one or coalitional competition, male–male contests result in a dominance hierarchy, and the male’s position in this hierarchy has important reproductive consequences (e.g., Dixson et al., 1993).Read more at location 2791
Male striving for social dominance is not the whole story. The alternative mating strategies used by less dominant males combined with female choice often undermine the reproductive strivings of dominant males (Perloe, 1992). One such male strategy involves a consortship, one-on-one male–female relationships, and sometimes long-term friendships (Dunbar, 1984; Smuts, 1985; Tutin, 1979).Read more at location 2795
For the female, the development of friendships with one or more males appears to be a strategy designed to elicit male support during times of social conflict and to elicit male investment in her offspring (Hrdy, 1979; Smuts & Gubernick, 1992). For the male, the development of such relationships increases the likelihood of siring offspring and sometimes results in direct investment in their own offspring (Buchan et al., 2003).Read more at location 2799
Male primates also show preferences in their choice of mating partners, although they are not as choosy as females. Males prefer to mate with females that are the most likely to conceive and the most likely to successfully rear offspring (M. N. Muller et al., 2006).Read more at location 2805
For species in which males provide individual benefits to a female and her offspring, some level of female–female competition over affiliations with such males is predicted and found (Palombit et al., 2001).Read more at location 2807
The consistent finding of larger males than females indicates that male–male competition was a prominent feature of human evolution and was very likely associated with a polygynous mating system (R. D. Alexander et al., 1979; Ghiglieri, 1987).Read more at location 2810
I suggest that the starting point of this feature of sexual selection was one-on-one male–male competition for control of harems, followed by the evolution of male kin-based coalitions.Read more at location 2812
explain the evolutionary reduction in the physical dimorphisms in our ancestors and the corresponding expansion of brain size.Read more at location 2814
I describe how these social complexities might have contributed to the evolutionary expansion in brain size and EQ in both sexes elsewhere (Geary, 2005b).Read more at location 2816
Most likely, female choice was influenced by the social and other resources the male could provide (K. Hill, 1982; Smuts, 1985).Read more at location 2819
Social support would have involved some form of protection of the female and her offspring as well as offspring care. A female preference for material support, such as meat provided through hunting, most likely emerged only after the evolution of a female preference for social support.Read more at location 2819
human sexuality, concealed ovulation and the more or less continuous sexual receptivity of women, evolved as an adaptation to increase the stability of female–male pair bonding and to facilitate paternal investment in offspring (H. E. Fisher, 1982; K. MacDonald, 1992).Read more at location 2822
The formation of multimale, multifemale communities would have resulted in benefits for strengthening (not creating) pair bonding mechanisms that may have already existed.Read more at location 2825
When considered in terms of mammalian reproduction, it is unremarkable that mothers throughout the world show a much greater availability for and engagement with their children than do fathers (Whiting & Edwards, 1988). As I reviewed in chapter 3 of this volume (in the section titled Parental Care), this is because the biology of mammalian reproduction results in higher levels of maternal than paternal investment and creates a faster potential rate of reproduction for males than females.Read more at location 3485
females are focused on parental effort and males on mating effortRead more at location 3489
the most remarkable feature of human reproduction is that many fathers show some degree of direct and indirect investment in their children.Read more at location 3490
it is nonetheless remarkable in comparison with the little paternal care found in the two species most closely related to humans and in terms of the more general pattern found with mammals (Clutton-Brock, 1989; Whitten, 1987).Read more at location 3492
The benefits of paternal investment include reductions in infant and child mortality rates in high-risk environments and improvements in children’s later ability to compete for essential social and material resources (Kaplan et al., 1998; A. Reid, 1997).Read more at location 3495
men’s parenting is associated with relatively high—roughly 90% to 95%—levels of paternity certainty and with restricted mating opportunities.Read more at location 3497
Childhood experiences may also bias men toward mating effort or parental effort through the nature of the parent–child attachment and the level of parent–parent conflict (Belsky et al., 1991).Read more at location 3501
culturally successful men have higher reproductive potential than do less successful men (Irons, 1979; B. S. Low, 2000). Culturally successful men are men who wield social influence and control the resources—money, land, cattle—that women would prefer to have invested in themselves and their children.Read more at location 4195
This preference is expressed in social psychological studies, reading materials, lonely hearts ads, and other measures (Lippa, 2007; Oda, 2001) and in their actual mate choices (e.g., Borgerhoff Mulder, 1990, 2000).Read more at location 4199
most women prefer monogamous marriages to wealthy, socially dominant, and physically attractive men—healthy men with good genes—and want these men to be devoted to them and their children. For most women, this preference is not achieved, and thus they have to make trade-offs. These typically involve trading his physical attractiveness for his cultural success. Some women attempt to achieve a compromise of sorts through relationships with several men.Read more at location 4201
Men consistently differ from women, regardless of where they are in the world, in terms of their enthusiasm for casual sex and in terms of the importance of the physical attractiveness of a potential mate.Read more at location 4213
The physical traits (e.g., age, WHR) men find attractive are readily understood because these traits are predictive of women’s fertility (Jasienska et al., 2004) and perhaps the health of their children (Pawlowski & Dunbar, 2005).Read more at location 4215
Women and girls may not injure and kill one another as frequently as men and boys, but they manipulate relationships and spread malicious gossip at least as frequently if not slightly more often (Archer & Coyne, 2005; Björkqvist, Osterman, & Lagerspetz, 1994; Card, Stucky, Sawalani, & Little, 2008; Feshbach, 1969; Grotpeter & Crick, 1996; R. Martin, 1997; Rose & Rudolph, 2006).Read more at location 4735
The heightened interpersonal intimacy among women and girls comes at a cost of greater vulnerability to social manipulationRead more at location 4750
girls who are the victims of relational aggression are 2.6 times more likely to suffer from depression or anxiety (for elaboration see Geary, 1998b) than are girls who are not victims or boys who are victims.Read more at location 4753
physically attractive girls, but not boys, were victimized more often than their less attractive peers;Read more at location 4757
Women compete on the basis of physical attractiveness, and those with an advantage are targeted for social and reputational attacks.Read more at location 4760
hide this aggression in the guise of rationality, advice, and casual comments should be at a competitive advantage.Read more at location 4764
Many perpetrators are at risk of exclusion from the very groups they are trying to control, but others appear to be more successful.Read more at location 4766
Socially aggressive and popular peers, however, are not well liked, especially by other girls.Read more at location 4768
aggressive girls, directed largely toward other girls, were more popular among boys than were other girls.Read more at location 4769
If the victim discovers the source of the rumor, especially in contexts in which there are few successful or attractive men and thus the competition over these men is stiff, female-on-female aggression can escalate to physical violence.Read more at location 4772
polygynously married women typically have less healthy children and fewer surviving children than do monogamously married women, although the reasons are not fully understood (Josephson, 2002; Strassmann, 1997; Strassmann & Gillespie, 2002).Read more at location 4791
The premature mortality was not due to diminished resources per child but may have been related to less paternal investment and competition from cowives.Read more at location 4798
“In addition to neglect and mistreatment, it was widely assumed that cowives often fatally poisoned each other’s children …. Cowife aggression is extensively documented in Malian court cases with confessions and convictions for poisoning” (Strassmann, 1997, p.Read more at location 4799
This competition may explain why the mortality of Dogon boys is 2.5 times higher than that of their sisters.Read more at location 4805
family provides a dowry to the couple or to the groom’s family in less than 6% of societiesRead more at location 4810
societies in which wealthy men invest the bulk of their resources in a single woman and their children, rather than in many wives and families.Read more at location 4812
Gaulin and Boster argued that dowry is a form of female–female competition to attract these high-status men as marriage partners.Read more at location 4813
In societies without a traditional dowry but with socially imposed monogamy, a woman’s financial prospects contribute to her attractiveness as a marriage partner. In the United States, men rate the financial prospects of a potential marriage partner as important,Read more at location 4814
do women’s financial and other forms of cultural success translate into reproductive success, as they do for men?Read more at location 4818
Using a nationally (U.S.) representative sample of 3,902 women age 45 years and older, B.S. Low et al. found a trade-off between years of education and thus earnings potential and number of children.Read more at location 4823
pattern for childlessness is the opposite that described for menRead more at location 4825
These SES differences in lifetime number of children are largely due to the delay in childbirth commonly associated with obtaining a higher education in modern societies.Read more at location 4828
In these species, males and females show sex-typical (e.g., higher testosterone in males) hormone levels, but there is preliminary evidence that prenatal exposure to androgens, circulating testosterone levels, and perhaps a heightened sensitivity to testosterone contribute to the aggressiveness of these females (e.g., Fivizzani & Oring, 1986; Langmore, Cockrem, & Candy, 2002).Read more at location 4838
There is, nevertheless, evidence that testosterone (produced by the adrenal glands in women), estrogens, and other hormones can influence women’s assertiveness and competitiveness and how these are expressed (Archer, 2006; Cashdan, 1995, 2003; Schultheiss et al., 2003),Read more at location 4842
Van Goozen, Cohen-Kettenis, Gooren, Frijda, and Van de Poll (1995) found that male-to-female transsexuals who were administered antiandrogens and estrogens reported a decrease in overt aggression and an increase in relational aggression after 3 months of hormonal treatments.Read more at location 4852
A core estrogen, estradiol, may be the key hormone. Schultheiss et al. (2003) and Stanton and Schultheiss (2007) found higher estradiol levels were associated with stronger implicit social power motives for single, but not romantically involved, women.Read more at location 4857
Similar to men, women with high implicit social power motives show an increase in stress hormone (cortisol) levels when they lose a competition (Wirth et al., 2006).Read more at location 4862
Status can be achieved in many different ways, from the intimidation and murder of competitors to the control of the ecological (e.g., land) and biological (e.g., cattle) resources that women need to reproduce to the attainment of a college degree and the securing of a well-paid job.Read more at location 4870
Men at the top of their society’s hierarchy are better able to realize their mating preferences,Read more at location 4872
Unlike most other species, men need other men to achieve and maintain status; men compete in coalitions and strive for status within their coalition.Read more at location 4873
Some men are satisfied with being in the middle of the pack, having enough status to marry but not enough to incur the wrath of the most competitive men. Other men want absolute controlRead more at location 4875
In societies characterized by kin-based or ideological coalitions, men cooperate with one another to control the social and material resources of the society. If any such coalition gains control, the men that compose the coalition use the society’s resources and their social power to actualize their reproductive preferences.Read more at location 4877
These societies stand in sharp contrast to societies in which monogamy is ecologically or socially imposed (Betzig, 1986; Flinn & B. S. Low, 1986); the latter are often democratic.Read more at location 4882
monogamy reduces reproductive skew among men—differences in the number of children sired by elite and low-status men are substantially reduced—and changes the cost–benefit trade-offs of male–male competition.Read more at location 4883
benefits of achieving high status are reduced,Read more at location 4885
monogamous mating systems are generally associated with less intense and deadly male–male competition.Read more at location 4886
Men’s competition in these societies essentially shifts from the use of physical violence for controlling the behavior of other people to the accumulation of indicators of cultural success (Keeley, 1996; Irons, 1979).Read more at location 4886
Monogamous societies are also characterized by a fuller expression of female choice and more exacting male choice.Read more at location 4889
As Trivers (1972) predicted, men’s parental investment results in women competing in monogamous societies for the more desirable bachelors.Read more at location 4893
Competition among women can be as creative and variable as that found among men and can range from the enhancing of their appearance to the spreading of lies about the sexual fidelity of other women to the murder of the children of cowives (A. Campbell, 2004; Strassmann, 1997). The last of these aside, female–female competition is typically more subtle than male–male competition. The corresponding tactics are relational aggression, that is, the use of gossip, rumors, and lies to manipulate and control social relationships in self-serving ways.Read more at location 4894
Most women will have the opportunity to marry and reproduce, whether or not they are culturally successful. To be sure, it is better to be successful for both women and men, but is it not as critical for women’s reproductive success as it is for men’s.Read more at location 4899
