A thought about differences between men and women and the Christmas story:
Do you know what would have happened if it had been Three Wise Women that came to the manger in Bethlehem, instead of Three Wise Men? They would have asked directions, Arrived on time, Helped deliver the baby, Cleaned the stable, Made a casserole, Brought practical gifts, and There would be Peace On Earth
A future without war. Is it possible? In fifty years? A hundred years? Two hundred years? A thousand years? What kinds of future societies will the human species create? What will the species itself become? Will there be endless war? And if not, how will the seemingly inevitable, endless cycles of war be terminated?
As an evolutionary biologist I believe that in order to understand why our societies are the way they are, whether there is any realistic possibility of abolishing war, and what kind of future societies we might build, we need to answer the question, “what kind of animal are we?” Pivotal to that understanding is a basic fact of human biology, viz. that we are a sexually dimorphic species. (Hand, 2018)
That’s the subject of the essay below, taken from my book War and Sex and Human Destiny. The title might well have been, “Why can’t a woman be more like a man?”
[What follows is an excerpt of several sections of the previous essay “Empower Women”]
Sexual dimorphism and parental investment theory, AKA, “The battle of the sexes” The term sexual dimorphism comes from the Greek dimorphos, meaning having two forms. At some time in their life cycle, most species of non-microbial organisms—plants and animals—reproduce sexually. They have males, which make sperm that are tiny and motile, or in the case of flowering plants are transferred via pollen. And they have females, which make eggs that contain nutrients needed to begin development into a new individual. Humans obviously fit this pattern.
Sperm typically have the equipment and energy for movement but are small. And eggs, which hold those needed nutrients, 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 concerning the degree to which each sex “invests” in producing offspring has affected the evolution of all sexually reproducing species. (Trivers 1972) And that includes us.
Examples of sexual dimorphism
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).
Sexual dimorphism, size differences, and social leverage
A biological principle relevant to any general discussion of social conflicts and conflict resolution has to do with body size differences. During social conflicts a very broad general rule across the animal kingdom is that larger and stronger animals always dominate smaller, weaker ones—unless the weaker ones have “leverage” in the relationship. (Hand 1986)
I began my explorations of 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 are always larger than females and thus could easily dominate a female. But during pair-bond formation their behavior changes so that they end up with a relationship in which 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. (Hand 1985)
Because close cooperation and coordination are required for successful breeding, the smaller females have “leverage” when it comes to resolving conflicts. 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 breeding conditions are such that if the larger males dominated females, resulting in reduction of the males’ reproductive success, the behavioral outcome we observe is egalitarian conflict resolving relationships rather than dominance/subordination ones. Looked at another way, males that share food or negotiate over nest relief duties experience better reproductive success than if they exert dominance.
How does this apply to our species? By roughly the same ratio that characterizes gulls, human males are larger and stronger than females of their race. 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 any given context? This is a subject too extensive for further consideration here, but chapters in a book edited by M. Z. Rosaldo & L. Lamphere explore examples of societies where circumstances give women such leverage. In them we see women exercising both domestic and public power and leadership. (Rosaldo&Lamphere1974) The point here is 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 the contexts described by Rosaldo and Lamphere the women also demonstrate that they are perfectly capable of leadership.
Sexual dimorphism in physiology
Sexual dimorphism isn’t as familiar in physiology; notable examples are differences in blood levels of the sex hormones testosterone and estrogen.
Sexual dimorphism in behavior
It’s sexual dimorphism in observed behavior, however, that is 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. The discussion that follows focuses on examples taken from mammalian species.
Examples of behavioral sexual dimorphism
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, and is not directly related to reproduction.
Male and female lions can live together, but it is 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.
Knowing what sexual dimorphism is and what to look for, we can now consider how behavioral sexual dimorphism plays out for us in ways relating to efforts to create a more positive, secure, just human destiny, and an enduring peace. We’ll consider first how it relates to psychological tendencies favoring physical aggression and then to preferences for social stability. (What follows is a summary of material presented earlier in two books, Hand 2003, 2014).
Recall that we are mammals, specifically 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.
Five Primate Realities
These first three biological realities affect women’s proclivities with respect to social conflicts and physical aggression.
Reproductive pressures on and priorities of women
Reality number 1. The pressure to reproduce. 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. Life, from a biological perspective, is all about reproducing successfully because that is the vehicle by which genes for traits, including behavioral/psychological ones, are passed to subsequent generations. Women who didn’t have children (such as myself) will not pass any genes affecting their social and sexual preferences to future generations. Traits for resolving social conflicts of women in the past who were successful reproducers are the traits women have today.
Reality number 2. The pressure of reproductive costs. 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 capable of reproduction, the earliest at ages between roughly eight and thirteen. Finally, research shows that after their offspring reproduce, women in most cultures are still deeply involved in ensuring that the offspring of their offspring also survive and thrive: they invest in their grandchildren. (Hawkes 2003)
Unquestionably for female primates, including women, reproduction is a very extended, risky, and expensive process that puts enormous reproductive pressures on females—most especially so for humans, since our offspring are born so very helpless.
Reality number 3: A preference for social stability. The evolutionary result of this massive female parental investment is that the ideal social situation for female primates, including women, is social stability for long periods. So, for women, war, any deadly fighting within their community, indeed, anything that threatens the life of these expensive offspring or their caregivers has been and remains hugely evolutionarily counterproductive.
This vulnerability is fundamental to women’s behavioral choices. Many observed behaviors characteristic of how women respond to conflicts reflect a strong, evolved, emotional/psychological preference for social stability. This proclivity—which underlies the observed social stability-seeking behavior we observe—is precisely what has made women reproductively successful.
To stress this point: women, characteristically, are generally much more inclined toward negotiation, mediation, and compromise, much more than men are. (Campbell 2013) 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. (Ury 1999)
Another example: To keep the peace when seriously challenged, women may defer rather than argue or fight; they are behaviorally primed to avoid fighting. In a context where it won’t cost them reproductively to do so, women may anticipate that challenging another person may produce a socially disruptive result; consequently, they may opt to prophylactically refrain, deflect, or defer.
Case in point: Anthropologists observed a nomadic foraging society that was generally egalitarian in behavior and politically egalitarian in that both women and men shared in decision-making that affected the entire group. Nevertheless, women regularly let the men sit under the shadier trees. Arguably, women in that society, anticipating that haggling with men over who sits where would lead to conflicts, choose to simply defer, to avoid conflict.
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. In relationships that are egalitarian we see that men sometimes defer “to keep the peace,” and negotiation with their wives will characterize much decision-making over potential conflicts.
Finally, a woman’s reproductive success—as well as a man’s—depends not only on producing a live child or children and keeping them alive until sexual maturity, it also depends on 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, and men as well, can be expected to have an innate concern to provide the best nurturing quality of life they can for their children as they mature.
Women are not pacifists or saints
Since this is a book about war, it’s important to stress that evolutionary pressure favoring a preference for social stability did not result in women being by nature pacifists, let alone saints. They can be spiteful. As members of a hierarchically inclined species they engage in power struggles, but typically establish and maintain their social status using nonviolent forms of aggression. But they can kill a sexual rival out of jealousy or a spouse they no longer love. They can engage in domestic abuse of children or spouses. But compared to men, women do so rarely.
Women can fight in wars if no other option is available. Soldiers who have fought with women have informed me 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. (e.g., Rosaldo 1974; Burbank 1992) The forms that women’s aggression takes, however, shows dimorphism.
So, women are not innate pacifists. What they are by nature is determined preservationists of socially stable communities. A wide range of women’s social behavioral choices—not just avoidance of war—are a reflection of that preference. (These choices are fully 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; also: Hand 2003, 2014)
Women, war, leadership
With respect to war, for the overwhelming majority of women physical fighting in defense of community is uncommon. If, however, women fear that they, their children, or their community are under some kind of imminent mortal threat, they may urge the men to make preemptive war. And as fierce defenders of children, community, and their way of life—women can and will fight, and fight bravely, if necessary. Journalist and film critic Kate Muir compellingly describes this in her interviews with women in the armed services. (Muir, Arms and the Woman, Female Soldiers at War, 1992)
As for women leaders, a review going back several hundred years shows that strong women leaders have waged wars of defense or preservation. (Hand, 2003, 99-104; 2014, 117-122). Think of Golda Meir (4th Arab/Israeli War), Margaret Thatcher (Argentina), or Elizabeth the First of England (mounting a navy that defeated the Spanish Armada). These heads of state did not launch an invasion or start a war, but they responded firmly to attacks.
In a warring society some small 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. (Hand 2003, pp. 95-105; Hand 2014, 117-122) 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 summary - This compressed account has covered how natural selection for reproductive success shaped the fundamental psychological relationship of women toward the use of physical violence, waging war, and a preference for living in and creating a socially stable community in which to raise children.
Reproductive pressures on and priorities of men
We turn now to two further biological realities, numbers 4 and 5, which also are the results of natural selection for reproductive success and/or survival. These apply to the other half of our species, the men. To end war, and to end or greatly reduce other factors that negatively characterize patriarchies, we also need to understand the second half of the sexual dimorphism phenomenon.
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 primate parental investment in offspring is never as great as that of the females. Many primate 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, bodily risks, 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 relatively easily father replacement offspring. They simply need to find a woman to impregnate; the father may or may not take responsibility for the long years of care required to bring the child to sexual maturity, which is a basic criterion for evolutionary reproductive success.
Reality number 5: As a consequence of the above, many male primates, including men, do not prioritize maintaining social stability to the same extent women do. Men have no desire to live in chaos, of course, yet social stability is less critical to their reproductive success.
Dominance status vs. social stability
Actually, the urge to rise in dominance status is, in many primate species, a major evolutionary pressure on and proclivity for males because higher dominance is frequently correlated with greater male reproductive success or survival. Some debate the extent to which this is true for humans. (Rueden & Jaeggi 2016) What is unquestionably true, however, is that much of men’s psychology and social lives focuses not on promoting social stability but on rearranging the social order to achieve greater social dominance, which translates into social status. (McMartin 2017)
Unless restrained by police or strong social customs and prohibitions, male groups will readily use physical aggression to achieve dominance over other male groups.
The overall result is that while social stability is a very high priority for women, it is not such a high priority for men.
Research and common experience shows that men are also more likely to use physical aggression that results in killing. (A classic study of this reality is Martin Daly and Margo Wilson’s Homicide, 1988.) Think of participation in fist-fights, knife-fights, gang wars, and inter-state war itself. These are characteristic of human male behavior, especially in dominator cultures, but also in any culture compared to the behavior of women.
The strong male urge to exercise dominance is also expressed in relationships between men and women, and as mentioned earlier. Unless a woman or women have some source of leverage in relationships, the woman or women are going to be subordinate. In modern societies a woman’s leverage often tends to be financial; the woman has her own substantial source of income that is critical to the family’s well-being or actually enables her independence. Or she may have family ties that, if exercised on her behalf, elevate her standing in a relationship. Or the culture in which the relationship is formed is one that promotes sexual equality so that cultural norms give the woman or women leverage.
Dominance vs. egalitarian relationships: Christopher Boehm and life in egalitarian tribes
Cultural anthropologist Christopher Boehm 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. (Boehm 1999) 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—the desire to control, defeat, or “win” over others rather than share or compromise as partners. When that urge or proclivity or desire grows into 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, a generator of war.
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