Heroes, Rogues, & Lovers: Testosterone and Behavior (29 page)

BOOK: Heroes, Rogues, & Lovers: Testosterone and Behavior

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"It's the only wheel in town." ⁴⁴

Given the uncertainty of love and the uneasy lives of men and women together, one might wonder why anyone gets married. According to a 1994 poll, a significant number of girls were wondering the same thing. Fewer girls than boys were planning to marry. While some single women elect to have babies, widely publicized statistics concerning the drawbacks of single parenthood discourage that. Why not be single and celibate? Why gamble? Why not do something else? Women are taking these questions to heart. Ann Lee and her Shaker disciples asked those questions, too. They decided to do something else and won converts to their point of view. In the 1840s there were six thousand members of the Shaker religious sect, which practiced celibacy and engaged in furniture-making as a livelihood. Today Shaker chairs are valuable antiques, but there are no Shakers to sit in them. Other people's children sit in them, and there are plenty of other people's children. When it comes to survival of the species, courtship is the only wheel in town.

In 1874, when they began to run out of converts, the Shakers solicited membership in ads that emphasized comfortable accommodations.
⁴⁵The ads didn't work. Hormones and the desire for genetic immortality stack the odds against celibacy. The great majority of men and women want to have children, and many of those who can't are willing to endure prolonged and expensive discomfort pursuing fertility.

We doubt that animals think about whether or not they should mate, but it does appear that animals use one of two broad mating strategies. One strategy is pair bonding, in which male and female come together and form a mutual tie. In pair bonding, animals go two-by-two, as they boarded Noah's Ark, to ride out the flood and face the future together. Usually they appear to like each other, but they don't have to. Gibbons, small arboreal apes, sometimes remain together like cranky

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old human couples, because neither partner has any other choice. The male chases away other males, and the female chases away other females, and the two are stuck with each other, for better or for worse. They are like many people, for whom habit counts more than love in holding a relationship together.
⁴⁶

Pair bonding is also the style of the hornbill, but reliability and trust, not crankiness, keep hornbills together. The female moves into a hollow tree, where she pulls out her feathers and uses them to line the nest in which she lays her eggs. She and her mate build a wall that seals her up in the tree, leaving only a small opening through which he can feed her small frogs and lizards. After the eggs have hatched, the male and female break down the wall together, and she comes out. If he is a lazy hunter, or gets into trouble, or runs away with another hornbill, she will stay sealed up and die. She needs to know that he will be reliable. During the courtship, before she lets herself be walled up, the male has to prove his reliability and gain her trust. Whereas the Samburu warrior wins a mate by stealing cows, the male hornbill wins a mate by bringing her many gifts of small frogs and lizards. The hornbills bond to ensure their future, and they invest equally in the same offspring.

The other mating strategy is that of a tournament, in which each male competes with all other males and the winner takes all. One male gets many females and the other males get no females. In pair bonding, a male needs enough testosterone to win one female, and the pair is then held together by something other than testosterone. In the tournament strategy, the dominant male depends more on testosterone. He needs enough to fight males and pursue females on a larger scale. With so much fighting and pursuing to do, his quality time with any particular female is limited to the courtship ritual and mating.

Elephant seals favor the tournament style of mating. A successful male elephant seal prevails over many other competing males and in the process accumulates a large harem. Females stay with him because he is their only choice, the only wheel in town. He breeds with the females and produces many offspring, but he provides no resources for the females or the offspring. Male and female elephant seals are ensuring their futures in different ways. The female invests a year of her life in one offspring, giving it her full attention and the richest milk produced by any mammal. The male fights to gain access to the females, invests sperm

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and a few moments for breeding, and completely ignores the offspring.

Neither strategy is "better" in an evolutionary sense. If it were, that strategy would have become the standard way of doing things. Viewed across all of nature, animals invest no more than necessary in their offspring. Among species where the young require care but not more than one parent can provide, one leaves and lets the other do the nurturing. This happens with many mammalsoffspring stay with their mothers. Among species where offspring are so helpless that they need care from both parents to survive, both parents will contribute. This is usually, but not always, the case with birds, where male and female cooperate to build a nest, incubate the eggs, and feed the babies together.

Human beings are flexible creatures, and they use both strategies. Which they will choose depends upon circumstances, personal preferences, and established practices of their culture. Some men make it clear that they are faithfully pair bonded. They tell their associates they are married, wear wedding bands, and center their lives around their homes and families. Other men chase women as though they were competing in a tournament. These men include pimps, philanderers, and bachelors who "play the field." They direct their energy outside of marriage and, if they have mates, they are not emotionally close to them, except occasionally and briefly. They say, "When I'm not near the one I love, I love the one I'm near."

We think of this tournament behavior as characteristic of men, but there is a women's version of it. A girl can have many boyfriends, and wives can be as unfaithful as husbands. Sometimes this is surprisingly useful. A woman with many men friends is likely to find support and a place to stay wherever she goes, and each man will be protective toward babies who might be hisit is to the woman's advantage to let each man think he is the father. A study of the Ache women in eastern Paraguay found that 17 women had 66 children by a reported 140 fathers, or 2.1 fathers per child!
⁴⁷Some female birds use a similar strategy. The English hedge sparrow female forms a lasting pair relationship with one male, but then she sneaks away and mates with another male. When she lays eggs and hatches them, each male seems to think that he may be the father, and both work to bring food to the chicks.
⁴⁸A tournament strategy is hard for a female to keep up, however. She can win the affection and support of many men, and thereby gather many

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resources for her offspring, but biology limits the number of children she can bear and thus limits her success with the tournament strategy. On the other hand, males are limited less by the number of children they can father than by the number of fights they can win, a number that can be very large indeed. Theorists are now beginning to examine shifts between these strategies and conditions under which human males and females show changing preferences between bonding with a single mate and seeking many mates.
⁴⁹

The pair-bonding and tournament strategies seem to call for different testosterone levels. Testosterone helps a male compete with others, and testosterone remains high as long as competition remains important. In tournaments, males have to compete with many others, and their testosterone levels stay high. Male birds that have many mates are high in testosterone throughout the breeding season. In pair bonding, testosterone is high long enough to compete for one mate, and then it drops. Male birds that, like the Lapland longspur, settle down with one mate are high only at the beginning of the breeding seasonhigh in testosterone when courting and mating, and low when taking care of their young.
⁵⁰This pattern can be disrupted by experimentally extending the period in which testosterone levels are high. Researchers injected Lapland longspur males with subcutaneous testosterone implants and compared their behavior to a that of a control group without testosterone implants. The high-testosterone males visited their nests less and fed their young less often than did the controls. Fortunately, the baby birds had hard-working mothers who made up for their temporarily macho fathers' neglect.
⁵¹

Male plainfin midshipman fish do not form pair bonds, but they take care of their young. Their testosterone patterns support a period of tournament breeding followed by a period of responsible parenthood. The plainfin midshipman fish fertilizes the eggs of as many females as possible and then guards multiple clutches at various stages of development. As long as the nests contain only eggs, the males remain high in testosterone and ready to fertilize new clutches, but when embryos begin to develop, their testosterone levels drop and they lose interest in sexual conquests. They devote themselves to their families.
⁵²

Testosterone levels are also important in the kind of sexual strategy that humans use. People who have high levels of testosterone seek

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many sexual partners, as reported among male military veterans and female college students.
⁵³Perhaps like birds, some people have chronic high levels of testosterone, and others have high levels only when they are pursuing mates. We know little about this possibility, although there is evidence from a study of Air Force officers that men's testosterone levels fall around the time they marry and settle down, and rise around the time they divorce and start looking for new mates.
⁵⁴Over shorter periods of time, testosterone has been observed to fall in men in the days immediately after their wives give birth.
⁵⁵Perhaps their bodies are preparing for helping their mates rather than competing with other men; or perhaps they are just tired. Changes in testosterone are associated with changes in size of certain areas of the brain. Psychologist Marc Breedlove has been studying the amygdala, which is known to be important in mating. His research with laboratory animals has shown that a part of the medial amygdala increases and decreases in size as testosterone levels increase and decrease.
⁵⁶

While it is clear that testosterone plays a role in love, sex, and reproduction, it is less clear what role it plays in sexual orientation. There is no difference in testosterone level between lesbians and heterosexual women, although among lesbians, those who identify themselves as "butch" tend to have higher levels than those who identify themselves as "femme."
⁵⁷One researcher, using hirsutism as an indirect measure of dihydrotestosterone, has reported preliminary findings that dihydrotestosterone levels are higher in gay men than in heterosexual men.
⁵⁸

Biologist Simon Le Vay has found that sexually dimorphic regions of the hypothalamus, a part of the brain known to be important in regulating male-typical sexual behavior, are two to three times as large in heterosexual men as in gay men or heterosexual women. Le Vay suggests there may be a genetic difference in the way the developing brains of gay and heterosexual men respond to androgens
in utero
.
⁵⁹It seems unlikely that adult testosterone levels influence sexual orientation, although they do influence sexual activity.

An Evolutionary Model

I began this chapter with love and testosterone and continued it with different kinds of relationship and mating strategies. At this point I want

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