Why Beautiful People Have More Daughters: From Dating, Shopping, and Praying to Going to War and Becoming a Billionaire–Two Evolutionary Psychologists Explain Why We Do What We Do

by Miller, Alan S.

  When mothers need help in their effort to raise their children, nobody is more likely or willing to deliver it than their kin. The mother’s kin are more motivated to invest in the children than the father’s kin, because the mother’s kin know for sure that they are related to the children, whereas the father’s kin may or may not be, due to paternity uncertainty. This is why it is Jane’s mother, not Jim’s, who comes to visit for two weeks, and it is Jane’s sister, not Jim’s, who babysits during the day. Jane’s mother and sister are certain to be related to the child; Jim’s mother and sister are not. This is why women today have a larger number of kin in their personal networks than men do. Women need to rely on their kin in case they need help, materially or otherwise.

  Two implications follow from this logic. First, if women maintain their ties to their kin in case they need help with their parental investment, then women who are materially better off should need less help from their kin, and therefore have less need to maintain their ties with them. Second, women who are currently married should need less help from their kin than women without husbands, because even with residual paternity uncertainty, the putative fathers should be motivated to make some parental investment in the children and thereby lessen the mothers’ burden. The presence of the spouse should be of at least some help. Further, the logic implies that family income and being currently married should have no effect on the extent to which men have kin in their personal networks.

  An analysis of a large American data set confirms both of these predictions. A woman’s family income and her currently being married both significantly decrease the proportion of kin in her personal network, whereas a man’s family income and marital status have no effect on the proportion of kin in his network.37 The Standard Social Science Model explanation cannot account for these patterns.

  Q. Why Do Girls of Divorced Parents Experience Puberty Earlier Than Girls Whose Parents Remain Married?

  Developmental psychologists have known for nearly two decades that girls whose parents divorce early in their lives, particularly before the age of five, experience puberty earlier than their counterparts whose parents stay married.38 Such girls are also more likely to start having sex at an earlier age, have a larger number of sex partners, get pregnant while still a teenager, and experience divorce in their first marriage.39 Since the biological purpose of puberty is to mark the onset of the reproductive career, it makes perfect evolutionary sense that girls who undergo puberty at an earlier age start having sexual intercourse, have more sex partners, and get pregnant at an earlier age. (Recall once again the dangers of naturalistic fallacy. Just because something makes perfect evolutionary sense does not mean it is good or desirable.) But why does the presence or absence of the father at home during early childhood affect the age of puberty and thus the onset and promiscuity of sexual activity?

  There are two competing explanations. One is that girls who experience puberty early are genetically different from those who experience it late. The other explanation is that girls have similar genetic makeup but respond to the environment differently, by starting puberty early or late. So which model is correct?

  In the case of pubertal timing, both models are likely to be partially correct.40 In support of the genetic model, there is substantial evidence that a girl’s pubertal timing is largely heritable; about 50–80 percent of its variance is explained by genetic differences.41 In this model, girls who undergo puberty early are simultaneously more likely to get a divorce because of their greater tendency toward sexual promiscuity, and to pass on their early puberty–greater promiscuity genes to their daughters. Hence, girls who grow up without a father (because their mother got a divorce or was never married) are more likely to experience puberty early and to become more sexually promiscuous because they have inherited the genes that will predispose them to do so.

  While evidence supports the genetic model, environmental influences can also affect the actual timing of puberty within a window set by the genes.42 This phenomenon is similar to other biological traits, such as height, weight, or intelligence. Height, for example, is highly heritable, so children of tall parents on average become taller than children of shorter parents; genes set the boundaries of potential adult height. Within these boundaries, however, environmental influences, such as nutrition or childhood exposure to disease, can determine the actual adult height.

  Between 20 and 50 percent of pubertal timing is unaccounted for by the genes, so environmental conditions can still influence the actual onset of puberty within the windows set by the genes. One of the most important early childhood influences is the absence of the father.43 In this model, girls who grow up without a father learn that men do not form lasting relationships with women and invest in their offspring. These girls then adopt a more promiscuous reproductive strategy of undergoing puberty early and forming short-term relationships with a large number of sex partners because they sense they cannot rely on men to form a committed relationship with them and provide parental investment in their offspring. In contrast, girls who grow up with a father at home learn the opposite lesson—that men do form lasting relationships with women and invest in their offspring. These girls then adopt a more restrained reproductive strategy of delaying their puberty and forming a committed long-term relationship with a partner who will invest in their offspring.44 Hence, the presence or absence of a father in a girl’s home before the age of five can explain both her age of puberty and her reproductive strategy.

  Hold On…

  There is a piece missing from this explanation, however. In order for this strategy to evolve among women, men’s tendency toward forming committed relationships and making parental investment must be stable across generations; the mother’s experience with her mates must be highly predictive of the daughter’s experience one generation later. One suggestion is that girls use the presence or absence of the father in the home as an indicator of the institution of marriage in the society.45 In this view, father absence signifies not the man’s unwillingness to form long-term relationships but a high degree of polygyny in society. In a highly polygynous society, married men are spread thinly among their multiple wives, and they cannot spend much time with any one of their wives or their offspring. Thus, the more polygynous the society, the less time any girl (or boy) spends with the father. In contrast, in monogamous societies, married men have only one wife, so they can spend all of their time with their wife and children. So the degree of father absence might be a microlevel indicator (within the family) of a macrolevel degree of polygyny (within the society).

  In polygynous societies, there is an incentive for girls to mature early because any pubescent girl can become a junior wife of a wealthy polygynist while a prepubescent girl cannot. In contrast, there is no incentive for girls to mature early in monogamous societies because all adult men in such societies are already married (and cannot marry again), given a 50–50 sex ratio, and pubescent girls can only marry young teenage boys, who do not have the wealth or status to support a family. Consistent with this logic, an analysis of cross-cultural data shows that girls undergo puberty significantly earlier in polygynous societies and in nominally monogamous societies with a high incidence of divorce (and thus a higher incidence of serial polygyny; see “Why [and How] Are Contemporary Westerners Polygynous?” in chapter 4).46 From this perspective, the average age of puberty has dropped precipitously in the United States in recent decades47 because the divorce rate (and thus the incidence of remarriage for men, that is, serial polygyny) has increased dramatically.

  The biochemical mechanism by which parental divorce precipitates early puberty in girls is not well known. The evolutionary developmental psychologist Bruce J. Ellis48 suggests that pheromones (a chemical substance that travels from one individual to another in order for the former to influence the behavior of the latter) emitted by the stepfather and other unrelated men in the house hold might trigger early puberty in girls. This is one of the remaining mysteries in evolutio
nary psychology.

  6

  Guys Gone Wild

  THE EVOLUTIONARY PSYCHOLOGY OF CRIME AND VIOLENCE

  While there have not been many evolutionary psychological studies in the area of crime and violence, one of the early classics in the field was on this topic.1 Martin Daly and Margo Wilson’s 1988 book Homicide demonstrates that all types of homicide—killing children, killing parents, men killing other men, men killing women, husbands killing wives, and wives killing husbands—can be explained by Darwinian logic.

  At first sight, it appears that killing children makes no sense from the evolutionary psychological perspective, which emphasizes reproductive success. Why would parents kill their own children? Daly and Wilson have two answers to this question. The first answer is that they don’t. Daly and Wilson discovered that what often passes as parents killing their children in police statistics is actually step fathers killing their stepchildren, who do not carry their genes. It looks as though biological parents are killing their genetic children in the statistics because the police, uninformed by Darwinian logic, make no distinction between biological parents and stepparents in their record keeping. Biological parents very seldom kill their genetic children.

  Their second answer to the question is that sometimes parents have to make tough choices. All parents, even wealthy ones, have limited resources to invest in their children. Every dollar, every minute, every effort that they invest in one child is another dollar, another minute, another effort that they cannot invest in other children. Their evolved psychological mechanisms therefore compel them to invest most efficiently, which usually means that they invest more in children who have the greatest prospect for reproductive success, at the cost of other children whose reproductive prospect is gloomier.

  Another surprising finding in this area is that criminals are not so different from other men. All men (criminal or not) are more or less the same. The ultimate reason why men do what they do—whether they be criminals, musicians, painters, writers, or scientists—is to impress women so that they will sleep with them. Men do everything they do in order to get laid.

  Of course, by the same token, all women are more or less the same, but you cannot see that in this chapter on crime and violence, because almost all criminals are men. Let’s first find out why that is the case….

  Q. Why Are Almost All Violent Criminals Men?

  There are many cultural universals—features of human society that are shared by all known cultures. Donald E. Brown provided the original list of “human universals” (and wrote a whole book about them) in 1991,2 and Steven Pinker updated the list in 2002.3 There are probably so many cultural universals (contrary to what Franz Boas and cultural determinists think) because human culture is a manifestation of human nature at the level of society, and human nature is universal to all humans.4 This is why all human cultures are more or less the same, and there are so many cultural universals. (See “What about Culture? Is Anything Cultural?” in chapter 2.)

  Among the many cultural universals is the fact that men in every human society commit an overwhelming majority of all crimes and acts of violence.5 Why is this? Why are men so much more criminal and violent than women?

  In their comprehensive study of homicide, the leading evolutionary psychologists Martin Daly and Margo Wilson note that humans throughout their evolutionary history were effectively polygynous—many married men had multiple wives.6 (See “Why [and How] Are Contemporary Westerners Polygynous?” in chapter 4.) In a polygynous society, some males monopolize reproductive access to all females while other males are left out; in such a society, some males do not get to reproduce at all, while almost all females do. (Recall our discussion of sex differences in fitness variance in chapter 2. The distance between the “winners” and the “losers” in the reproductive game is much greater among men than among women.) This in equality of reproductive success between males and females makes males highly competitive in their effort not to be left out of the reproductive game. This competition among men leads to a high level of violence (murder, assault, and battery) among them, and the large number of homicides between men (compared to the number of homicides between women, or between the sexes) is a direct result of this male competition for mates.

  Big Violence Starts Small

  In particular, Daly and Wilson7 note that most homicides between men originate from what is known as “trivial altercations.”8 A typical homicide in real life is not one depicted in an episode of Columbo: premeditated, well planned, and nearly perfectly executed by an intelligent murderer. Instead, it begins as a fight about trivial matters of honor, status, and reputation between men (such as when one man insults another or makes moves on another’s girlfriend). Fights escalate because neither is willing to back down, until they become violent and one of the men ends up dead. Because women prefer to mate with men of high status and good reputation,9 a man’s status and reputation directly correlates with his reproductive success. Men are therefore highly motivated (albeit unconsciously) to protect their honor, and often go to extreme lengths to do so. Daly and Wilson thus explain homicides between men in terms of their (largely unconscious) desire to protect their status and reputation in their attempt to gain reproductive access to women.

  Incidentally, this is why many evolutionary psychologists believe that the death penalty does not deter murder. The logic of the death penalty assumes that most murders are premeditated. A potential murderer carefully and rationally weighs the costs and benefits of the act, and decides not to murder if the costs outweigh the benefits. This might describe a fictional murderer on Columbo, but not real-life murderers, who do not stop to think before escalating their trivial altercations into fatal fights.

  The logic of the death penalty also assumes that execution is the worst fate possible. From the evolutionary psychological perspective, there is something worse than death, which is the total reproductive failure that awaits any man who does not compete for mates in a polygynous society. If they compete and fight with other men, they may die (by being either killed by the other man or executed by the state); if they don’t compete, however, they will definitely die, reproductively, by leaving no copies of their genes.

  Rape may appear to be an exception to this reasoning because, unlike murders and assaults, the victims of rape are usually women, and there is therefore no male competition for status and reputation. However, the same psychological mechanism that compels men to gain reproductive access to women by competing with each other can also motivate men to commit rape. Predatory rapists are overwhelmingly men of lower class and status, who have very dim prospects of gaining legitimate reproductive access to women.10 While it is not a manifestation of competition and violence, rape may be motivated by men’s psychological mechanisms that urge them to gain reproductive access to women when they do not have the legitimate means to do so.

  We can also extend the same analysis to property crimes. If women prefer to mate with men with more resources, then men can increase their reproductive prospects by acquiring material resources. Resources in traditional societies, however, tend to be concentrated in the hands of older men; younger men are often excluded from attaining them through legitimate means and must therefore resort to illegitimate means. One method of doing so is to appropriate someone else’s resources by stealing them. So the same psychological mechanism that motivates violent crime can also motivate property crimes.

  Crimes Evolved Before Norms Against Them

  Our suggestion that men steal in order to attract women might at first glance appear strange, since theft and other forms of resource extortion are universally condemned in human societies; in fact, such condemnation is another cultural universal. It is quite possible, however, that the psychological mechanism that motivates young males to commit violent and property crimes evolved in our ancestors in evolutionary history before the ape-human split (five to eight million years ago), even before the ape-monkey split (fifteen to twenty million years ago). In
fact, our reasoning logically requires that the crucial psychological mechanisms emerge before the informal norms against violence and theft do; otherwise, violent competition and accumulation of resources through theft would not lead to higher status and reproductive success for males because they would be ostracized for violating the norms. We believe that the norms against violence and theft might have evolved in reaction to the psychological mechanisms that compelled young males to engage in violence and theft. The fact that violent and predatory acts that humans would classify as criminal are quite common among nonhuman species that do not have informal norms against such acts increases our confidence in this suggestion.11

  These are some of the reasons why men are more violent and criminal. Crime and violence pay in reproductive terms, by allowing men to eliminate or intimidate their rivals and to accumulate resources to attract mates when they lack legitimate means to acquire such resources. But that is just one side of the coin. What about women? Given what we present above, why would any woman commit crimes at all?

  Staying Alive

  The evolutionary psychologist Anne Campbell offers the “staying alive” theory of female criminality, which answers these questions and more.12 Her theory begins with the fundamental observation that offspring’s survival and thus reproductive success depends more heavily on maternal than paternal care and investment. It is therefore imperative for mothers rather than fathers to survive long enough to take physical care of their offspring to ensure their survival to sexual maturity. This, Campbell argues, is why females are more risk-averse than males are. The potential benefit of taking risks—by engaging in physical competition for resources and mates, for instance—simply does not justify the potential cost (the very survival of their offspring, which heavily hinges on the mother’s own survival). A woman’s primary goal is therefore to stay alive for the sake of her children.