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 (23 page)

Both the likelihood of travel abroad and expressions of xenophobia reflect men's need to attract women using social and cultural ornamentation. Men's status and mate value, unlike women's, are socially and culturally specific, and they cannot successfully attract women outside of their own society and culture. Married men, on the other hand, can use their wives as cross-culturally meaningful social ornamentation to signify their mate value. In sharp contrast, the standards and criteria by which women are judged for their mate value are socially and culturally universal, and thus women have no need to fear foreign cultures.

A FEW TOUGHER QUESTIONS

In the preceding chapters, we have used evolutionary psychology to explain a wide variety of puzzles in many areas of social life, from sex and mating to marriage and the family; from crime and violence to economics, politics, and religion. We hope we have succeeded in convincing you that evolutionary psychology is an approach that can provide at least some (partial) answers to many persistent questions about human behavior. Given the range and number of questions that we have attempted to address in this book, you may rightfully wonder if there is anything that evolutionary psychology
cannot
address.

In the appendix of his 1994 international bestseller
The Moral Animal: The New Science of Evolutionary Psychology
(the book that introduced evolutionary psychology to both of us), the science writer Robert Wright lists six questions that evolutionary psychology could then not answer. We would like to return to these six questions and see how far evolutionary psychology has come in solving these puzzles in the last thirteen years.

 

1.
What about homosexuals?

How can evolutionary psychology explain homosexuality, when it places so much emphasis on reproductive success (accomplished largely through heterosexual sex) as the ultimate motive of all behavior? This is usually among the first questions that we receive from students, neighbors, and academic colleagues alike when we present our evolutionary psychological ideas. In his 2000 book
The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature
, the evolutionary psychologist Geoffrey F. Miller admits that he cannot explain homosexuality.
¹
To the best of our knowledge, no one else can. There is still no definitive and accepted explanation of homosexuality in 2007, thirteen years after Wright posed the question “What about homosexuals?”

There are some ideas, however, not from evolutionary psychology but from the related field of behavior genetics. The geneticist Dean Hamer and his team have discovered the genetic roots of male homosexuality. While they have not discovered the “gay gene” (the actual genes that increase the probability of male homosexuality), they have located a region of a chromosome that is involved—a genetic marker at Xq28.
²

Even if a “gay gene” or genes are eventually discovered and sequenced, it still does not explain how such genes can survive if their carriers are exclusively or predominantly homosexual. The evolutionary biologists Robert L. Trivers and William R. Rice have an idea. Their theory of the evolution of male homosexuality is described in Hamer's book
The Science of Desire: The Search for the Gay Gene and the Biology of Behavior
.
³
Trivers suggested the theory to Hamer in a phone conversation, but he and Rice never published their theory.
⁴

Trivers and Rice believe that genes for male homosexuality may be passed on to the next generation, not by the gay men themselves but by their sisters and other female relatives. They posit that the so-called gay genes may incline their carriers, male or female, toward the same behavior: the desire to have sex with men. If the carriers are male, then they become male homosexuals (and they do not pass on their genes to the next generation). If the carriers are female, however, they will have more children than other women who do not carry such genes because they will have a larger number of male sex partners and have sex with them more frequently. The reduced reproductive success of gay men is compensated for by the heightened reproductive success of their sisters, and the male homosexuality genes will survive.

Their idea, which might be dubbed the “horny sister hypothesis,” is a very provocative one, but it has been supported by a recent study that shows that female maternal relatives of male homosexuals have more children than female maternal relatives of male heterosexuals.
⁵
(Because they are on the X chromosomes, the “gay genes” are passed on to gay men by their mothers, not their fathers.)

We also note, however, that the most likely reason that male homosexuality has survived to this day is that throughout most of recorded history, gay men were forced to hide their sexuality by social norms and legal sanctions, and so got married and had children like straight men.
⁶
If so, the liberation of homosexuals, which allows them to come out of the closet and not pretend to be straight, may ironically contribute to the end of homosexuality.

So far no one has found a genetic basis for female homosexuality.

 

2.
Why are siblings often so different from one another?

This is one of the clear examples of the triumph of recent evolutionary psychological theory and research. This was an unresolved question in 1994 but has now been answered, thanks to two somewhat unconventional heroes of evolutionary psychology: Frank J. Sulloway
^[7]
and Judith Rich Harris.
^[8]

In his 1996 book
Born to Rebel: Birth Order, Family Dynamics, and Creative Lives
, Frank J. Sulloway argues that siblings within the same family must occupy different familial niches.
⁹
Firstborns (the eldest siblings), who are born into a family without any siblings with whom to compete for parental resources, typically grow up to identify with the parents and, by extension, other authority figures. Later-borns (younger siblings), in contrast, are always born into a family in which there are older siblings who have already taken the niche of identifying with the parents. So they must carve out their own niche by distancing themselves from the parents and becoming rebels. Sulloway's massive historical data show that in religious, political, and scientific spheres, firstborns are more likely to become the conservative vanguards of the old tradition, and later-borns are more likely to become the leaders of new revolutions. Thus, birth order, whether one is the eldest or younger, is one factor that makes siblings raised in the same family different in their personalities.

In her 1998 book
The Nurture Assumption: Why Children Turn Out the Way They Do
, Harris methodically demolishes the universally held assumption that how parents raise their children is a major determining factor in how they turn out.
¹⁰
Harris instead argues that parental socialization has very little effect on children because they are mostly socialized and influenced by their peers. While Harris's conclusion was enormously controversial and widely condemned by politicians and the media alike, it is in fact corroborated by behavior genetic research.
¹¹
Behavior geneticists contend that the rough rule of thumb when it comes to the determinants of child development is 50-0-50—that is, roughly 50 percent of the variance in personality, behavior, and other traits is heritable (determined by the genes); roughly 0 percent by shared environments (what happens within the family, shared by all siblings); and roughly 50 percent by the nonshared environment (what happens outside the family, often not commonly shared by siblings).

Harris's work highlights the importance of the nonshared environment on child development, and therefore gives us another reason why siblings raised in the same family are different. Of course, contrary to how the media portrayed (and viciously attacked) Harris's work, it decidedly does
not
mean that parents are not important for children's development. Parents are
enormously
important because children receive 100 percent of their genes from their biological parents. It simply means that within broad limits, how parents socialize their children is not very important to adult personality.

Both Sulloway's and Harris's research and conclusions have been hugely controversial, but mostly in the media and among nonacademic audiences. The scientific community in general and evolutionary psychologists in particular tend to be supportive of their ingenious research and counterintuitive conclusions. Because Sulloway's theory emphasizes family dynamics as a primary determinant of adult personality, whereas Harris's group socialization theory focuses on what happens outside the family, Sulloway and Harris are naturally critical of each other's work.
¹²

 

3.
Why do people choose to have few or no kids?

4.
Why do people commit suicide?

In contrast to the success of evolutionary psychology and behavior genetics in solving the first two questions on Wright's 1994 list, the next two questions present us with still unresolved puzzles. As far as we know, there is no compelling evolutionary psychological explanation for why some people choose to remain childless or why people commit suicide. Behavior geneticists have recently discovered the genetic basis for fertility behavior;
¹³
we now know that whether one has many children or a few is partially influenced by genes. However, this still does not explain why some people choose to have none; clearly, genetic tendency toward childlessness could not be selected for.

In some ways, the genetic influence on how many children people have goes against evolutionary logic. It suggests that people who have many siblings (because their parents had many children) themselves have many children, and people who have few siblings (because their parents had few children) themselves have few children. The evolutionary logic would suggest the opposite. If you have many siblings, you don't have to have many children yourself because you can still attain great reproductive success by investing in your siblings; both your children and your siblings carry half your genes. In contrast, if you have few siblings, you have to have many children yourself because you don't have the option of investing in your siblings. The heritability of family size therefore remains a puzzle for evolutionary psychology.

 

5.
Why do people kill their own children?

We do not know why this question was on Wright's 1994 list, because Martin Daly and Margo Wilson had already solved it in their 1988 book
Homicide
, which is partly based on their even earlier work.
¹⁴
Daly and Wilson first point out that the answer to the question, “Why do people kill their own children?” is, “They don't.” Most parents who are convicted of killing their children are actually stepfathers, who are not genetically related to the children they kill. Crime statistics make it appear as though some biological parents kill their own children, because the police, uninformed by evolutionary psychology, make no distinction between biological parents and stepparents in their statistics.

From the evolutionary psychological perspective, it makes perfect sense for stepparents to neglect; underinvest in; and, in some cases, even kill their stepchildren, so that their spouses will focus their investment of time and resources in the couple's common genetic children, current and future. Among many species, such as baboons and lions, when a new male takes over a group of females with young, the first thing he does is kill all the existing children systematically, so that all the females will reproduce with him. It would be surprising if humans were any different.

Even the few cases where biological parents kill their genetic children can be explained by Daly and Wilson's notion of “discriminative parental solicitude.”
^[15]
They point out that all parents have limited resources to invest in their children. Their task is to maximize their reproductive success—not by maximizing the number of children but by maximizing the number of grandchildren. From this strictly Darwinian perspective, any resources invested in children who are not likely to survive to sexual maturity or find mates and reproduce themselves are entirely wasted. Thus, parents are far more likely to neglect, abuse, and kill their biological children who are deformed, handicapped, ill, or even physically unattractive and to shift their parental investment of their limited resources toward those children with more promising reproductive prospects.
¹⁶
As uncomfortable as we may be with such a conclusion, the truth appears to be that parents do favor some of their children over others, even among their own genetic children, to say nothing about stepchildren to whom they are not genetically related, and they overwhelmingly favor those who are intelligent, beautiful, healthy, and sociable.

 

6.
Why do soldiers die for their countries?

To the best of our knowledge, there is no satisfactory explanation for this phenomenon from an evolutionary psychological perspective. However, we have a few observations. First, it seems to us that soldiers die for their countries only if their country honors fallen soldiers and provides for their widows and children; in fact, we cannot think of any civilized society that does not honor men who fight and die for their country. Second, many men get married right before they are shipped to war, which explains why so many deployed soldiers have newborn babies whom they have not seen. Perhaps fighting and potentially dying for their countries when the country honors the war dead and provides for their widows and children is some men's reproductive strategy to make sure that their children are taken care of, when they could not provide sufficient parental investment themselves. Historically, soldiers have disproportionately come from lower classes. We may also add that while the last thing men do before they go to war is to get married and impregnate their new brides, unfortunately, sometimes the first thing they do when they conquer their enemy is to rape the women in the conquered society,
¹⁷
which also helps increase their reproductive success further. Soldiers would not get this opportunity unless they were willing to fight and die for their countries. But we admit that these are simply our observations, and we do not have a clear explanation for why soldiers die for their countries. Neither does anyone else.