A book review by Michele O’Mara, PhD

Barash, David and Judith Eve Lipton (2001). The Myth of Monogamy: Fidelity and Infidelity in Animals and People. New York, NY: Owl Books.

“Aspiring monogamists are going against some of the deepest-seated evolutionary inclinations with which biology has endowed most creatures” (1), according to Zoologist David P. Barash, and his wife Judith Lipton, a psychiatrist.   And this book is determined to illustrate exactly why this is true. In a sometimes humorous, sometimes seemingly self-indulgent exploration of animal behavior that is mostly focused on birds and insects, the authors cite numerous research studies to illustrate their theory that humans, like animals, are predisposed to extra pair copulations (EPCs). This is the fancy scientific term for having sex with someone other than your mate.

As the authors prepare to unfold their observations about how human monogamists are climbing an uphill battle, they clarify that this book is designed to illustrate what is natural, not what is right or wrong.   The exploration throughout this book is not about what should be, it is simply about what is.

Thanks to DNA fingerprinting, the lens used to observe animal behavior has significantly improved and animals previously thought to be monogamous are not so. Monogamy is divided into two categories: social and sexual. Social monogamy exists “if they live together, nest together, forage together, and copulate together” (8). Sexual monogamy requires sexual fidelity, also known as intra-pair (or in-pair) copulation (IPC).

The currency of evolutionary success is based on successful reproduction. To understand how this relates to males and monogamy, the authors introduce various associated strategies employed by males throughout the animal kingdom such as:   sperm competition, frequent copulations, mate guarding and parental investment.

Sperm competition speaks to the effort put forth by males to secure a female whose egg he can fertilize, leading him to reproductive success. Endless sperm and limited eggs create an unbalanced picture – basic supply and demand dictates the inherent competition among men to get their sperm to fertilize eggs. The authors provide many examples of how males compete to copulate with a given female.  For obvious reasons, frequent copulations increase the chances of reproduction, and it is theorized that this contributes to the frequent desire to copulate among males.

Mate guarding is another strategy used by males to improve the odds that they are successful in fertilizing their female, and furthermore to guarantee that the offspring they are raising are their own! This tactic prevents his mate from straying, as well as preventing other males from gaining access to her.   An interesting side note about mate guarding that is correlated with human behavior is the notion that “poor-quality males are generally more concerned with mate-guarding than are their high-quality counterparts, and for good reason, since females whose mates are less desirable are more inclined to seek EPCs” (35).

When it comes to parental investment, there are many variations among animals and humans. Resources such as time, energy, risk taking, childcare, protection, beauty, skills, strength and more are combined to determine one’s value. This makes just as much sense with humans too. The greater your strengths, resources, and beauty, the more leverage you have to attract a similarly valuable partner. As for sperm which is readily available in large quantities, however, its value pales in comparison to “the big, fat, energy-rich mother lode of nutrients called an egg” (17). The authors suggest that because of this, males are positioned to compete with one another for access to the much rarer eggs, hence the sperm competition.

Interestingly, “the greater the male’s secondary sex characteristics, the less his contributing” (50).   The authors go on to say, “It is as though desirable males know they are desirable, and so they are likely to shop that desirability around; by the same token, those ‘lucky’ females who get to mate with such studs find themselves less lucky when they are stuck with most of the household chores” (50). The comparison is drawn to less desirable men, and it is suggested that those less endowed with good looks actually make better fathers.

Before we get too carried away with all of this male gallivanting, let’s be clear that females are none-too-innocent themselves.   For a long time, females were considered the opposite of males, and evolutionary biologists envisioned females desiring monogamy.   However, “evidence has been accumulating, fast and furious, that females are not nearly as reliably monogamous as had been thought” (58).

If reproductive success is the fundamental biologically-based motivation for males to stray, what’s the motivation for females? The authors suggest a handful of reasons including: fertility insurance, to avoid inbreeding, a predilection for quality, and to maximize the benefits of sperm competition, material rewards, recruit care and protection of offspring, to gain toleration of young when different troops interact, and possibly to pave the way to a stronger prospective pair-bond.

Fertility insurance is a simple concept. The more sex she has, the more sperm she’s exposed to, and the stronger the likelihood that she will reproduce.   In order to avoid inbreeding, the authors suggest females may seek out strangers that are less likely to have any genetic association, thus reducing the possibility of inbred offspring. The search for quality sperm is thought to be the motivation for multiple mating, and it involves not only the search for the most attractive, healthiest, and strongest male, but it also takes incorporates what is called the “last male advantage.” The female may mate with her partner, along with many others and typically the last male she copulates with has the greatest advantage for a successful fertilization. This also allows her to maximize the sperm competition, pitting the strongest of the strong males against one another, and saving her the effort of having to determine for herself which one is the best. The notion behind this is thought to be that the one who succeeds is going to help her create offspring that will be as successful in doing the same so that her reproductive success, and quality, remains high for years to come.

Material rewards are another suggested motivation for multiple pairings. The authors cite a study of Red-billed gulls, stating that “Females who are well fed during courtship resist all EPC attempts, and they also remate with their partner the following year; on the other hand, females who had been poorly provisioned are especially likely to divorce in the future and are more likely to submit to EPCs” (91-92).   It is thought that some females seek multiple EPCs so that they can cast a wide-net of protection for their offspring, leading many males from all over to question whether or not the offspring is his, and thereby increasing the odds of protection, and at a minimum reducing the odds of harm.

The pursuit of a stronger pair-bond is another motivation suggested for females who engage in EPCs. Because there is an advantage of having two parents over one, the argument that a female would seek an alternate pair-bonding to improve her social situation certainly makes sense.

Why, the authors query, does monogamy occur at all? Their conclusions are varied. One suggestion is that monogamy leads to better and more effective parenting. Another thought is that it may be a response to sperm competition by males, so that they can reduce the risk that another male will fertilize his female’s egg.   They also suggest the possibility that monogamy is a solution to men fighting over women. Monogamy may be the result of men negotiating how to divide access to women. In general it appears these arguments lead toward the suggestion that monogamy was greatly influenced by the “cultural homogenization that came with Western imperialism and the Judeo-Christian ethic of monogamy” (146).   In the end, however, the author admits that with the question of why monogamy exists at all, “the short answer is that no one knows” (132).

The book also reports some interesting facts about monogamy and the double standard for men.   G.P. Murdoch cited 238 different human societies around the world, and monogamy was enforced as the only acceptable marriage system in just 43. Gwen Broude researched 116 different human societies and reports that 63 permit extramarital sex by husbands, and only 13 permit it for wives.   However, Kinsey and colleagues discovered that slightly more than 25 percent of adult females in the United States were unfaithful. Given this double standard, it is ironic that in terms of sexual capacity, women are physiologically capable of having more sex than men.     Furthermore, a woman can be impregnated without experiencing a hint of pleasure, whereas it is likely (though not necessary) for a man to orgasm upon ejaculation, thereby rewarding him for his efforts with pleasure.

The last, and possibly shortest, chapter of the book draws a relatively simple conclusion that while all of the evidence points to why humans are biologically oriented to polygamy/polyandry, we humans are gifted with a large, discerning brain that allows us something all of the animals cited in the book do not have: choice.

In summary, this book was very informative; at times entertaining and it introduced me to some new and valuable perspectives on the evolutionary imprints on our sexuality. The first several chapters were weighted with very detailed research on animals.   For a layperson such as me, it is hard to make the connection between the sexual behaviors of a fruit fly and those of a much more complex creature such as a human.   This perhaps is more my weakness, than the books, however.

I appreciate the authors’ goal to simply observe the evolutionary trail and impact on human sexual behavior as it relates to monogamy, and to set out to do so without judging the outcomes as right or wrong.   In this way the author succeeded. I would imagine this book has some cross-over appeal for the mental health community as well as zoologists and social scientists. It covers a lot of bases (no pun intended).

However, it was very disappointing to see the observations limited to male-female copulations. The fundamental premise of this research was reportedly to unearth the myth of monogamy.  Specifically, however, this body of work only explains the sexual behavior and evolution of heterosexual monogamy, not sexual monogamy in general. The inclusion of same-sex pair-bonding between animals such as penguins, whiptail lizards, dragonflies, and others who are known to engage in same-sex pair bonding, would lead to a more accurate and informed view of our whole evolutionary history.

In the final chapter, the conclusion emphasizes the ability of humans to make choices. Unfortunately, this chapter seems to propose only two choices: to be monogamous or to be unfaithful. The reality is that we live in a culture that includes a multitude of coupling arrangements, some of which include the expressed desire to engage in a polygamous arrangement whereby partners support and encourage EPCs as an option for one, both, or all partners to the relationship. Because animal research relies on observation and interpretation, I would think it is nearly impossible to determine the motivations, and expressed agreements (or lack thereof) among these animals about their copulation.   Humans, however, are easier to study in this way, yet there is no discussion about the choices humans makes to engage in multiple-pair arrangements and how successful or not those are. There is no mention, in fact, that this is a choice some humans do make. This seems a significant oversight in a book determined to dispel the myth of monogamy.

At the end of the day, this book has offered very interesting perspectives that provoke much thought about human sexual behavior and issues of monogamy, while simultaneously remaining judgment-free about exactly what to do with this information. That has been no easy feat.