Discrepancies in wealth can bring out men's worst evolved traits, including violence, poor treatment of women, and polygamy, for example by much-married South African President Jacob Zuma.
Even for a head of state, South African President Jacob Zuma has an awfully colorful sex life. In April, the 70-year-old married his sixth wife, Bongi Ngema, in a traditional Zulu ceremony. But, unlike serial monogamists, Zuma remains married to three other wives.
His second wife, Nkosazana Dlamini-Zuma, a respected minister in Zuma's government, divorced him in 1998. And his third wife, Kate Matsho-Zuma, committed suicide in 2000. By his wives, fiancées (yes, there are likely to be more weddings), and at least four other women, Zuma has allegedly sired at least 20 children.
All that marrying doesn't slow down Zuma's extra-marital activity, either. He was acquitted of the 2005 rape of an acquaintance he knew was HIV positive. The judge accepted his defense that the sex was consensual, and evidence suggests this was no isolated affair.
I am not an expert in South African politics, or even politics in general, yet I am fascinated by the private marital (and non-marital) relations of this head-of-state. And he's not alone: the leaders of Qatar, Swaziland, Sudan, Chad, and Saudi Arabia are also polygamous. As an evolutionary biologist, I've learned that our evolutionary past interacts with our current circumstances to influence the relationships and domestic arrangements we forge. Zuma is, in many ways, the product of an environment that reinforces some of our worst evolved traits.
South Africa's immense economic inequality, crippling levels of violence, rampant sexism, rape epidemic, and 5.6 million HIV infections are not merely a list of unconnected facts. It matters that South Africa's president is a polygynous, philandering male who admitted at his rape trial that in order to reduce the risk of HIV infection, rather than wearing a condom, he showered after sex.
The crucial connection comes through an evolutionary phenomenon that began as our ancestors encountered inequality in wealth, power, and reproductive opportunities, and which disposes some men to behave in reckless, risky, and violent ways. You might call it "the problem with men," and though it's not something that manifests in all males, it is endemically masculine, and at its most extreme it can poison societies. But, much as we have dealt with obesity epidemics not by blaming obesity sufferers but by understanding the ways that evolved human physiology and psychology can create innate vulnerabilities, so too can a better understanding this evolutionary phenomenon help us to deter its damage.
A Brief History of Wealth
For most of our evolutionary history, our ancestors hunted animals and gathered plant-based foods. You and I are largely products of adaptation to this lifestyle of hunting and gathering in small groups, where everybody knows everybody else. People in these small foraging bands depended on one another and shared according to one another's needs. As a result, foraging societies can appear egalitarian to modern observers.
Throughout history, wherever hunter-gatherers began to tend gardens and herd animals of their own, they've settled around long-term bases. Groups grow bigger and the bonds of reciprocity loosen, allowing some individuals to accumulate wealth, including the land they work and the animals they keep.
Several times in the last few thousand years, human societies domesticated and mastered the farming of at least one cereal: wheat and barley in Mesopotamia, Egypt, and India; millet and sorghum in Africa; rice in southern China; corn in Mexico and Peru. Arable land, accumulated grain stores, and livestock became the first widespread forms of wealth. But wealth that can be stored and traded can also be stolen, and thus must be defended. Coalitions of neighbors or kin who could effectively repel raids from other groups, or who could raid neighboring groups themselves, thrived. Those who failed to organize often succumbed.
Effective defense required organizers and strategists. These were humanity's first elites, whose strength, intelligence, and social skills elevated them to positions from which they coordinated the group's defense. Predictably, they also used these positions to enrich themselves and entrench their power. In other words, agriculture gave rise to money, to inequitable distribution of money, and thus to all of the evils of which money is root.
Inequalities in wealth also decided, in large part, who succeeded in finding mates, raising children, and eventually sending them out into the world to find mates of their own. The increasing material inequality from gardening, herding, and then farming led to big differences in reproduction and infant survival between the wealthy and the poor. But that's really just part of the story.
When anthropologist Laura Betzig recently tracked down reproductive records for a variety of societies, including hunter-gatherers, gardeners and herders, and agriculturalists, she compared the numbers for men and women. And she found that widening inequality affects men's and women's reproductive success differently.
Because every baby has a mom and a dad (at least in genetic terms), the average number of children produced by men in a given society is similar to the average for women in that society. But a woman can only experience a relatively limited number of pregnancies before menopause, constraining her maximum number of babies to the low teens. Men suffer no such biological constraint. If the planets aligned perfectly for a man, he could theoretically sire hundreds, even thousands of children. We expect, then, the number of children produced by an individual to vary more widely among men than among women.
Betzig found that hunter-gatherer women reported only slightly less variation in offspring number than men. But with pastoralism and herding, men's variation in reproductive success grew, so that the most successful men were able to sire 20. One Kenyan Kipsigis man claimed 80 children. (This also means that there were more men who sired no children at all.) But women's reproductive success grew only slightly more variable.
Betzig also scrutinized the written records from agricultural civilizations in Mesopotamia, Egypt, India, Mexico, Peru, and China. The early emperors and kings who ruled each of these societies made themselves despots of more than just economic wealth. They also dominated the means of reproduction, gathering for themselves the most fertile women from within the society and from their military conquests as wives, concubines, and slaves. In every one of these six early civilizations, the most successful men boasted 100 or more documented children. Understandably, no woman in these societies made comparable claims.
Inequality, Fitness, and Violence
History, says the truism, is written by victors. Agriculture and civilization might sound like a good deal for men, but in evolutionary terms it favored the few who wielded great wealth and power. Biblical accounts say King Solomon kept 700 wives and 300 concubines. Wealth and influence afforded Solomon phenomenal reproductive success, but at the expense of his male subjects, who necessarily had fewer chances to reproduce.
Anthropologists have long found associations between the rate of polygynous marriage within a society and its likelihood to wage war on neighboring groups or tribes, as well as its internal violence and homicide rate. Violence can actually cause polygyny, as warrior societies lose a lot of young men in conflict, leaving many more surviving women than men. As a result, some women face the unenviable choice of either sharing a husband or not marrying at all.
Often, ancient warfare would involve raiding other villages to capture fertile women as brides. The strongest, most war-adept groups of men can defend their own villages and women, raid other villages and capture brides. The fiercest groups quickly become the most polygynous, with the fiercest warriors taking the most wives.