Why Are Men and Women So Different: Sun and Moon, Ying and Yang
Excerpt from War and Sex and Human Destiny by Judith Hand
What Is This Thing Called Sexual Dimorphism?
The term comes from the Greek dimorphos, meaning having two forms. Most species of non-microbial organisms, plants and animals—at least some time in their life cycle—reproduce sexually. They have males, which make sperm that are tiny and motile, and females, which make eggs that contain nutrients sufficient to develop into a new individual. Humans obviously fit this pattern.
Sperm have the equipment and energy for movement but are small. And eggs, which hold nutrients for to begin the development of a new individual, are relatively huge and immobile. This massive difference in size, composition, and function has profound biological ramifications, because eggs, having all that nutrient material, are much more expensive to make than are sperm. Males can make thousands or even millions of sperm. But in every sexually reproducing species, females produce far fewer eggs.
This fundamental asymmetry sets up a situation in which reproductive pressures on and strategies pursued by males and females of all sexually reproducing species are very different. Natural selection will shape the two sexes differently in some critical ways. The biologist Robert Trivers, in his paper “Parental investment and sexual selection,” wrote what is arguably the most influential paper explaining how this fundamental male/female difference has affected evolution of all sexually reproducing species. And that includes us.
Anyone who closely observes animals sees these differences played out in many forms of different or competitive male/female behaviors, the result of natural selection on the two sexes over time. Observers often refer to some male/female behavioral interactions as a “battle of the sexes.”
Sexual dimorphism can occur in anatomy, physiology, and behavior. It exists in external anatomy (e.g., male/female differences in body shape, color, or size) and internal anatomy (e.g., on TV shows like “Bones” or “CSI,” experts often look at skeletal or dental remains to tell whether a human victim was male or female).
A general biological principle relevant to this book’s discussion of social conflicts and conflict resolution has to do with size differences; during social conflicts, a general rule is that larger and stronger animals always dominate smaller, weaker ones—unless the weaker ones have “leverage” in the relationship, a principle I proposed in a paper entitled “Resolution of social conflicts: dominance, egalitarianism, spheres of dominance, and game theory.”
Mated male (standing) and female Western Gulls.
I began my explorations on conflict resolution with a field study of the communication behavior of Western and Laughing Gulls, including changes in behavior when males and females formed pair-bonds. Keep in mind that in these particular species close cooperation between males and females is essential for them to breed successfully. They share in nest building and nest guarding duties, territory defense, and in protecting and caring for their young.
Male gulls, always larger than females, could easily dominate a female. But during pair-bond formation their behavior changes so that they end up with a relationship where conflicts are resolved using what we would call egalitarian behaviors. For example, hungry mates would share a large food source side-by-side; the male did not drive the female away until he had his fill. When doing incubation duty they used signals to negotiate which mate would be the one to incubate eggs at a given time; the male did not use physical force or threats to make the female leave the nest when he was ready to incubate.
Because close cooperation and coordination are required for successful breeding the smaller females have “leverage” in their pair-bond relationship. Sharing food and using signals to negotiate which of them should be on the nest are two egalitarian forms of conflict resolution. What this study indicated is that if domination of females by larger mates reduces male reproductive success, as it would in this species if the male did not share food and duties with the female, then male/female conflict resolving relationships can be egalitarian rather than dominance/subordination. I describe this research in a paper entitled “Egalitarian resolution of social conflicts.”
How does this apply to us? By roughly the same amount that characterizes gulls, human males are larger and stronger than females, so we should expect men always and everywhere to dominate women. Whenever they don’t, we need to ask why; what cultural or reproductive leverage is likely cancelling out women’s size disadvantage in that context? This is a subject too extensive for consideration here, but chapters in a book edited by M. Z. Rosaldo & L. Lamphere, Women, Culture, and Society, explore examples of societies where circumstances give women such leverage and we see women exercising both domestic and public power. The point being that in human relationships and societies, whenever women gain sufficient “leverage” in any given context they can be expected to have egalitarian relationships with men in those contexts, and they are perfectly capable of leadership. Sexual dimorphism in physiology isn’t as familiar; notable examples are differences in blood levels of the sex hormones, testosterone and estrogen.
It’s sexual dimorphism in behavior, however, that’s critical to discussing human social affairs. Looking across the animal kingdom we see behavioral complexities that relate to multitudes of different species living in widely divergent habitats, from fish to reptiles to birds, to mammals. Humans are classified scientifically as mammals because women nourish their newborns and young with milk from mammary glands. That being the reality, the discussion that follows focuses on examples taken from mammalian species.
While differences directly related to reproductive interactions like mating behavior occur, behavioral differences also occur that are not directly related to reproduction. For example, an elephant herd consists of females and their offspring, including sexually immature males. But when a male comes of age, the females expel him, allowing contact only during breeding season. Expelling males of reproductive age is a built-in proclivity, or preference, that regulates elephant social affairs but is not directly related to reproduction. Male and female lions can live together, but it’s females that have the proclivity to unite to kill prey to feed the whole pride. Males do participate in hunts, especially of large prey, but the main urges of a pride male are to guard the pride from other males and mate with females as often as possible when the females are in heat. For gorilla families, food consists primarily of green leafy vegetation, and the females’ biological urges motivate them to spend their days eating and caring for their young. They also prefer to let the male determine the direction of the group’s movements: when he moves they follow. If danger threatens, he’s the one with the proclivity to protect the group.
Recall that we’re mammals and we’re primates, closely related to other Great Apes: gorillas, orangutans, chimpanzees, and bonobos. A number of realities that are true for other mammals and primates are also true for humans. The following are three biological realities that affect women’s proclivities with respect to social conflicts and especially physical aggression.
Reality Number 1. The biological bottom line for all living things is to reproduce. Women must successfully reproduce. If an animal doesn’t reproduce, its genes and the physical and psychological characteristics they govern are eliminated from the game of life. From a biological perspective, life is all about successful reproduction because that is the vehicle by which genes for traits, including behavioral/psychological ones, are passed to subsequent generations. I didn’t have children so the genes for my social and sexual preferences won’t be passed on. Fundamentally, traits of women in the past who were successful reproducers are the traits we have today.
Reality Number 2. For female mammals, including female primates, reproducing is a very expensive investment, beginning with production of eggs (as opposed to sperm), and then additionally, investment in time, risks taken, and energy expenditure. What does that mean for women? Consider that female primates carry an offspring to term, nourishing it from within their body—often for months; for women, nine months. Then they risk the serious hazards of childbirth. Then for a substantial period of time they provide milk from their body for nourishment, something very costly from a physiological perspective. They must protect this offspring, care for it, and in our case, support it for years before it is old enough to reproduce, the earliest at ages between roughly eight and thirteen. Finally, after their offspring reproduce, research by Kristen Hawkes and others shows that women in most cultures are still deeply involved in making sure that the offspring of their offspring also survive and thrive: they invest in their grandchildren. So do men, but not as frequently or consistently as do women. The “grandmother effect.” Reproduction is unquestionably for female primates, including us, a very extended, risky, and expensive process that puts enormous reproductive pressures on females. Most especially so for us since our offspring are born so very helpless.
The evolutionary result, Reality Number 3, is that the ideal social situation for female primates, including us, is social stability for long periods. Anything that threatens the life of these expensive offspring or their caregiver, for women certainly something like war but also deadly fighting within their community, has been and remains hugely evolutionarily counterproductive. This reality is fundamental to women’s behavioral choices. Many observed behaviors characteristic of how women respond to conflicts are a reflection of an evolved, strong emotional/psychological preference for social stability because that proclivity, and the observed behaviors which it underlies, is what made women reproductively successful. This is because that proclivity, and the observed behaviors which it underlies, is what made women reproductively successful. For example, women, in general, are naturally inclined toward negotiation, mediation, and compromise, much more than men, in general. Why would natural selection, over time, favor women thus inclined? Because, as many writers and experts like William Ury have pointed out, solutions arrived at by those nonviolent means often result in win-win outcomes, which tend to be more socially stable, meaning they avoid or decrease social conflict. The results are also longer lasting .
Another example. To keep the peace when challenged, women may defer rather than argue or fight; in a given context where it will not cost them reproductively to do so, women may anticipate that challenging another person may produce a socially disruptive result and so they may opt to refrain or defer (for example, in a who-will-sit-under-the-shady-tree case mentioned in the book excerpted here). When under stress, in conditions that might elicit fighting, men typically react with what is called the “fight-or-flight” response. Several researchers pointed out that women similarly stressed are often inclined toward what has been called the “tend-and-befriend” response, something much more likely to facilitate a calming effect on the situation.
Many otherwise strongly independent women in many societies will choose to defer to their husbands’ wishes in small things rather than create an argument. This will especially and perhaps consistently be the case if the woman does not have sufficient social leverage to make her relationship with her husband egalitarian. Finally, a woman’s reproductive success depends not only on producing a live child or children and keeping them alive until sexual maturity, hence her concern with conditions fostering social stability, it depends also on the woman providing a nurturing environment in which to raise children who will be able to 1) successfully compete for reproductive partners and 2) to succeed in life so that their own children thrive. Hence women can be expected to have an innate concern to provide the best possible nurturing quality of life she can manage for her children as they mature. It is important to stress that evolutionary pressure favoring a preference for social stability did not result in women being by nature pacifists or saints. They can be spiteful. As members of a hierarchically inclined species they engage in power struggles, but women typically establish and maintain their social status using nonviolent forms of aggression (bad-mouthing a rival, excluding someone from their clique, resorting to witchcraft). They can kill a sexual rival out of jealousy or a spouse they no longer love. But compared to men, women do so rarely. Women can even fight in wars if no other option is available, and soldiers who have fought with women claim that if roused to the point of taking up a weapon, women can be vicious fighters. Lack of aggressive motivation is not what is being asserted about women’s biology. The forms that women’s aggression takes, however, shows dimorphism. What women are by nature is determined preservationists of socially stable and nurturing communities. A wide range of women’s social behavioral choices, described in Women, Power, and the Biology of Peace (pp. 138-144) and Shift: The Beginning of War, the Ending of War (pp. 62-65, 165-167)—not just avoidance of war—are a reflection of that preference).
With respect specifically to war, if women can be convinced that they, their children, or their community are under some kind of imminent mortal threat, women will urge their men to wage preemptive war. For the overwhelming majority of women (not all women, but the overwhelming majority), physical fighting in defense of community is an uncommon behavior. But as fierce defenders of children and community—and that includes their way of life—women will fight, and fight bravely, if necessary. This reality was well described by writer and film critic Kate Muir in her book Arms and the Woman. Female Soldiers at War.
A review going back several hundred years shows that strong women leaders have waged wars of defense or preservation (Women, Power, and the Biology of Peace pp. 99-104; Shift: The Beginning of War, The Ending of War pp. 117-122). Think of Golda Meir (4th Arab/Israeli War), Margaret Thatcher (Argentina), or Elizabeth the First of England (Spain). In a warring society some percentage of women will certainly be political “hawks.” Historically, however, and this is key, women leaders in power have been overwhelmingly less inclined than male leaders to launch a war of conquest. Elizabeth the first of England is an example of the former protective sort, as evidenced by her mounting a navy that defeated the Spanish Armada. If history can be believed, Cleopatra of Egypt exemplifies the less common woman leader, having a genuine lust for conquest. In short, we can expect that female heads of state are as likely as male heads of state to be strong defenders of their nation, but are less likely than male leaders to start wars. In this compressed summary we have covered how natural selection for reproductive success shaped the fundamental psychological relationship of women, in general, to using physical violence, to waging war, and to a preference for living in and creating a socially stable community in which to raise children. We take up the issue of individual differences later. We turn now to two further biological realities, also the results of natural selection for reproductive success and/or survival. These apply to men, in general, and to their relationship to physical violence and war.
Reproductive Pressures on and Priorities of Men
Male pygmy marmoset with offspring.
Reality Number 4: For male mammals, the reproductive game is very different; males virtually never invest in offspring as heavily as females do. With only rare exceptions found in one primate family (Callitrichidae – tamarins and marmosets), male primates never invest in offspring as heavily as female primates do. In many primates, males invest nothing but sperm. Human fathers often become involved in some support and protection of their young (think monogamy), but this isn’t even the case in all cultures. With only rare exceptions would a father’s physical participation, risk, and time investments approach those of a mother. And very importantly, if a man loses an offspring for any reason—from a fight within the community where he lives or in a war—men potentially can father replacement offspring relatively easily. They simply need to find a woman to impregnate, and the father may or may not take responsibility for the years-long care required to bring the child to sexual maturity, which is a basic criterion for evolutionary reproductive success. As a consequence of the above: Reality Number 5 is that for many male primates, including men, maintaining social stability is not as high a priority as it is for women. It is important to men, who have no desire to live in chaos, but not nearly as critical reproductively as it is to women.
Actually, the urge to rise in dominance status is, in many primate species, a major evolutionary pressure on and priority for males because higher dominance is frequently correlated with greater male reproductive success and/or survival. There remains some debate around the extent to which this is true for humans. What is unquestionably true, however, is thatmuch of men’s social lives and psychology is focused not on promoting social stability but on rearranging the social order to achieve greater social dominance that translates into social status (see for example J. McMartin, Personality Psychology; A Student Centered Approach pp. 180-182). Sometimes this involves using physical violence (in cultures where violence isn’t strongly suppressed). Think of participation in fist-fights, knife-fights, gang wars, and inter-state war itself. These are characteristic of human male behavior in dominator cultures. And in any culture, they are uncommon to rare behavior for women compared to men. Research and common experience shows that men are more likely to use physical aggression that results in killing, a classic study of this reality being that of Martin Daly and Margo Wilson’s Homicide.
The cultural anthropologist Christopher Boehm wrote an important book, Hierarchy in the Forest: The Evolution of Egalitarian Behavior. In it he describes life in egalitarian African tribes, noting how hard these egalitarian, nonviolent people work to ensure that “upstart males” (more rarely females) cannot assert themselves in a way to increase their dominance. At minimum, they’re ridiculed. Say a hunter brags about what a big gazelle he brought down. A woman may laugh and say how nice, since what he brings in is usually so puny. If ridicule doesn’t work, “upstarts” can be sanctioned by group shunning for a time. Or even the extreme of ostracism; if he won’t quit efforts to rise in dominance (status) over others, they toss him out.
We, men and women, have inherited from primate ancestors the urge to form dominance hierarchies. This urge or proclivity—the desire to control, defeat, or “win” over others rather than share or compromise as partners—when that desire becomes the overarching passion in a human heart, it becomes a poisoned wellspring of the evil that humans do to each other. It’s the killer of lives and societies, and a generator of war. It is virtually self-evident that if we are to build communities that remain stable and secure from violence, including war, tendencies for increasing one’s domination that might result in physical violence, especially killing and certainly war, must be suppressed one way or the other—using customs, education, laws and even punishment. And women in general are, by nature, psychologically geared to respond to potential or actual conflicts or situations that might develop into physical conflicts by using nonviolent behaviors that foster social stability. How sexual dimorphism with respect to using physical violence versus strong inclinations that foster social stability affects social decision-making in many aspects of our social lives is explored further in War and Sex and Human Destiny, including a look at male proclivities that make us susceptible to making war.
My Perspective on Gender Differences
The reality of human sexual dimorphism, as described above, has shaped my perspective on “gender differences.” Research, time, and social change continue. We in the United States are, for example, deeply involved now in debates about things that would have been unthinkable when I was in graduate school. Debates about whether there are really only two sexes, male and female. What about “transgender” individuals, and their rights in a democratic and free society? What about children, or adults, who are born with the several physical characteristics that define the two sexes (most fundamentally the capacity for producing sperm or producing eggs) but who feel the social and sexual preferences of the other sex? Should they undergo a sex-change operation?
Although I do not do so in the detail that full exploration of the subject of sexuality requires, in War and Sex and Human Destiny I do briefly address this issue. I do so to avoid problems with sexual stereotyping, but most relevantly as personality relates to questions of leadership. If we decided we want to pursue a “better” future, one that is more peaceful, just, and environmentally sustainable, what traits in what kinds of leaders do we need to look for?
One way I look at this very complex issue is by saying that we, all of us, have a male side and a female side. To illustrate what I mean, consider some other things about me. Let’s start with the fact that as a child I was definitely a girly-girl in many respects. My first remembered “toys” were two lovely little dolls, maybe ten inches tall, dressed fairy-tale like as the Snow Queen, all in white, and Sleeping Beauty. They were my dearest treasures. I played jax when boys were playing marbles [well, I did try marbles but lost interest]. I identified strongly with fairy tales about princesses and loved Rapunzel with her beautiful long hair. But I never, ever, played dolls. In fact, I can only remember seeking out and playing with boys. And when we played Tarzan, I never would accept being the helper Jane….I always wanted to take the active role of Tarzan. Then, when I was about ten, I discovered Wonder Women. I was hooked. This was my role model. I began to get every copy of the comic book and kept them. If they had not been stolen from my mother’s garage when I was in college I would be a rather wealthy woman today. One winter, when we lived in Boulder Colorado, I made my three buddies help me build a pile of snowballs, and then I directed them throw them at me like they were bullets as I deflected them with the imaginary bracelets on my wrists.
One of the reasons I was told “no” so many times in my life, like the issue of auto mechanics versus home economics, was because I was always choosing to do or study things that were forbidden to girls or women. Had I wanted to marry and become a homemaker the path of my life would have been much different, much easier. And in the end, I even picked a profession, science, which at the time was still a rare choice for a young women. In short, I consider myself to be a living embodiment of the concept that we all have both female and male sides…aspects to our personalities.
Here, from War and Sex and Human Destiny, is how I address the notion that we all have a male side and a female side, and how that relates to issues of leadership:
“The table, randomly selected from an Internet Google search, lists personality traits in the United States commonly thought of by many as female and male. In actuality, every person is a complex combination of what their society considers to be male and female traits. In everyday terms, in differing degrees we all have a female side and a male side.
“But consider that some of us are way more in touch with our female side: say a person—boy or girl, man or woman—who is very emotional, non-assertive, sensitive, a bit too self-critical, and also sweetly nurturing and empathetic. And some of us are way more in touch with our male side: someone—boy or girl, man or woman—who is aggressive, competitive, very self confident/self-oriented, non-self-critical, in fact rebellious and risk-taking. And some of us display a mixture of traits that can be described as being in touch more equally with both male and female sides. A man who is not only aggressive, self-confident, competitive, and bold, but also self-reflective and empathetic. A woman who is not only nurturing and empathetic, but also independent, competitive, and bold. Human embryonic development is so complex that someone can be born having physical sex characteristics of one sex but feeling the biological preferences and urges characteristic of the other sex. Essentially, all societies have available to them, if they choose to take advantage of it, a rich variety of individuals. This is a massive, arguably splendid, diversity that can either be embraced or molded into rigid stereotypes.
Sex and Leadership
“So to start a social revolution headed toward a positive “better” destiny, what kind of leaders should we follow? Who should we elect to lead the change? Obviously, a leader cannot be shy. He or she must be in touch with aspects thought to characterize their male side like being assertive, independent, and bold. But wisdom demands that she or he is also able to be self-critical and reflective, able to change their mind when needed; stubbornly holding to an unworkable, unfavorable position is fatal to good leadership. And to lead well, rather than be a bully or tyrant, he or she needs to be in touch with traits thought to characterize a female side, like being accepting and empathetic with regard to the people they lead.
“Our very worst choice for leaders would be anyone, man or woman, having traits guaranteed to foster continuation of the world’s dominator, warring, patriarchal cultures. Someone aggressive, competitive, non-self-critical, strongly self-oriented and woefully lacking in being accepting or empathetic. They should not be elevated to leadership. They should not be tolerated as leaders. Not if we want to “try something different” that might bring about a lasting, less destructive and vastly more nurturing future.”
In actuality, every person is a complex combination of what their society considers toe be male and female traits. In everyday terms, in differing degrees we all have a female side and a male side. Essentially, all societies have available to them, if they choose to take advantage of it, a rich variety of individuals, a massive, arguably splendid, diversity that can either be embraced or molded into rigid stereotypes. -- Judith Hand