Beauty, Cooperation, and the Hadza Hunter-Gatherers

Part II Beauty, Cooperation, and the Hadza Hunter-Gatherers

By Polly Cleveland

In The Evolution of Beauty, Yale ornithologist Richard Prum elaborates on Darwin’s theory of the effect of sexual selection on evolution. Beyond “survival of the fittest”, the sexes have asymmetric interests. Males, with their cheap sperm, seek to sire as many offspring as possible. Females with their expensive eggs and limited lifetime reproductive opportunity, seek to pick the best mates. Males compete with one another for control of females. Females seek to avoid male control and to choose their mates freely. In many species, male competition results in bigger, stronger, and more weaponized males, as in huge sea lion males with long tusks. Prum focuses on female choice.

Female choice, given free rein, can lead to arbitrary standards of beauty and behavior in a species. Among neotropical manakins, females do all the work of raising chicks while males contribute only sperm. Males dance, sing, and flash their colors on communal display grounds known as “leks”; the females arrive, watch, pick a male for a quickie, and leave. The females favor only a few of the males; the rest may never get to mate. Blue manakins have even evolved a cooperative dance among a group of five or six males; females choose between groups of dancers, mating with the alpha male.

Prum moves from birds to humans. Humans, he points out, are far more cooperative than our African ape relatives, gorillas, chimpanzees and bonobos. Men and women don’t differ as dramatically in size as male and female apes. Unlike apes, humans tend to monogamy, he says, because females need help raising the kids. Prum also cites surveys showing that women do not prefer big, square-jawed macho males; rather, they go for men with moderate physiques and gentle behavior. Prum goes on from here to many interesting observations on possible effects of female choice, such as why do men, unlike apes, have long, dangling penises?

Yet in offering a generalized account of human behavior, Prum misses a human society that supports the female choice theory especially well. That society is the Hadza, as described in Nicholas Blurton Jones’ new book: Demography and Evolutionary Ecology of Hadza Hunter-Gatherers (2016).

The Hadza are an ancient hunter-gatherer tribe living in northern Tanzania near Lake Eyasi. Traces of their culture in the area date back at least 130,000 years. The area is too dry for agriculture and the tsetse fly makes it unsuitable for livestock. But there’s an abundance of seeds, nuts, berries, honey, and especially, underground tubers. The Hadza live in small groups, moving every few weeks depending on seasonal availability of foods. While all other group-living animals, including apes, consist of close kin, Hadza groups are quite fluid, with unrelated individuals continually coming and going. Like all hunter-gatherers, the Hadza are extremely egalitarian and cooperative.

Hadza men spend their days hunting with poison arrows. But they don’t hunt the small game they learned to capture as boys. Rather, they hunt for big game, like baboons, antelope, zebra, or buffalo—which they very rarely catch. Some men never catch anything. But when a man does nail a big animal, the meat is equally shared among the whole group, gaining him prestige. One anthropologist has called this a “show-off” strategy.

Hadza women do almost all the work, including caring for children and gathering and preparing food. They get little contribution from their husbands–maybe an occasional piece of honeycomb or a small bird, which the men expect their wives to prepare. In compensation, however, it’s the women who chose their husbands (often for only a few years). What sort of men do Hadza women prefer? Successful hunters–not good providers!

When the men are not hunting, they sit around in “the men’s place” chatting, smoking, eating tubers prepared by their wives, and fiddling with their bows and arrows. There’s almost no violence among the men. Disputes are resolved by long discussions, or at the worst, one of the men will leave and join another group. If you look at pictures of Hadza, both sexes are small, thin and wiry–no great differences in size or appearance. Both sexes go for bead necklaces.

Like the blue manakins, the Hadza seem to fit Prum’s model of extreme female choice. The women don’t depend on their husbands for much besides sperm. They’re free to choose the “show-off” hunters, who sire more children, but may actually contribute less to their children’s nutrition. Judging by the peacefulness of the men, female choice seems to have tamed male-male competition.

While all hunter-gatherer societies are highly egalitarian, not all allow as much freedom to women. In the Amazon rain forest, Ache men supply some 80% of the food by hunting. These men may ritually sacrifice children over women’s objections, and engage in lethal quarrels. Hadza women seem to derive their independence from the terrain, where it takes no more than a sharp digging stick and knife, a leather sling and water gourd, plus long hours working in the hot sun, for women to fully provision themselves and their children—and grandchildren. Another unrelated African hunter-gatherer society, the !Kung, lead a very similar life.

The latest evidence from Africa shows hominids manufactured flint tools as long as 3.3 million years ago. Once there were stone knives, female hominids must have used slings to carry them—along with food and infants. A Hadza life style could date back millions of years. Anthropologist Sarah Blaffer Hrdy, in Mothers and Others: The Evolutionary Origins of Mutual Understanding (2009), attributes human cooperativeness to women’s shared mothering of children—a trait quite absent in apes. She draws examples from the Hadza. Blaffer Hrdy’s female cooperativeness together with Prum’s female preference for cooperative males might explain the evolution of the most cooperative species on earth: humans.

In Aristophanes’ comedy, Lysistrata (411 BCE), Lysistrata persuades all the women of Athens and Sparta to withhold sex until their men agree to end the long-running Peloponnesian war. Was Aristophanes onto something?


Beauty and Profit

By Polly Cleveland

Beauty and Profit: The Evolution of Beauty (2017) by Richard O. Prum

In 1860 Charles Darwin wrote to his American colleague, Asa Gray: “The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!” What was Darwin’s problem?

Darwin (1809 – 1882) had just published his masterpiece On the Origin of Species (1859), in which he laid out his theory of evolution by natural selection. Darwin had rushed The Origin into print so as not to be beaten out by his co-discoverer, Alfred Russel Wallace (1823-1913). Unlike Wallace, Darwin worried about many seemingly maladaptive features of living organisms – like the male peacock’s beautiful but cumbersome tail.

In 1871, Darwin published his second big book, The Descent of Man, and Selection in Relation to Sex. Here, Darwin argued that, besides natural selection, two sexual mechanisms were at work. Horns and other weapons as well as large body size of many males, he claimed, derived from the “Law of Battle”– the competition between males (mostly) for access to the opposite sex. He called the second mechanism “Taste for the Beautiful”. This happened when one sex, usually female, selected mates by some arbitrary aesthetic criterion – like eye spots on a peacock’s tail. Aesthetic selection could “run away”: When females selected a male for his long tail or his red cockade, they would produce male offspring with long tails or red cockades and female offspring with a taste for males with long tails or red cockades.

In The Evolution of Beauty, Yale ornithologist Richard Prum picks up the story. The Victorians were quite content with the “Law of Battle”, but “Taste for the Beautiful” – no way! The very idea that females could exercise active sexual choice appalled that prudish society. Wallace himself led the reaction, becoming more “Darwinian” than Darwin in his insistence that natural selection could account for all features of living things. As Prum details, Wallace’s view dominates evolutionary science to this day. Natural scientists have twisted themselves into knots explaining peacocks’ tails as somehow adaptive. A popular hypothesis is that the very burden of the tail indicates to a female that a male is extra fit and healthy.

Prum will have none of this. Of course, as he points out, there’s a trade-off between ornament and fitness. A bird with too long a tail won’t survive as well as one with only a moderately long tail. But nonetheless sexual selection can impair fitness*. He gives a telling example: the club-winged manakin. The male of this tiny neotropical bird makes a violin-like squeak by rubbing its wings together at high speed; to squeak, it has evolved distorted solid-boned wings that make it an inefficient flyer. Moreover, the female has the same wings, though hollow-boned and less extreme. (This happens because embryos start out identical and only later differentiate by sex; that’s why males have nipples.)

Prum recognizes the parallel to economics. He reports a conversation with his Yale colleague, Robert Shiller, who complains about the “efficient market hypothesis,” so popular before the crash of 2008. The “efficient market hypothesis” assumes that in the markets for stocks, bonds, other securities, and even land, the prices reasonably reflect future profitability. The hypothesis course turned out to be disastrously wrong in the stock market bubble of the roaring 20s, and in the world wide real estate bubble leading up to the crash of 2008. But I believe the problem goes deeper.

Conventional neoclassical economics assumes that in a capitalist society, competition forces all businesses to relentlessly maximize profit or fail. Marxian economics makes the same assumption. That’s why conventional economists celebrate capitalism, because it supposedly leads to efficiency and innovation. That’s why Marxists condemn capitalism, because it seems to require ruthless anti-social behavior. To me, the assumption that “cutthroat competition” alone shapes the economic world is equivalent to the “Darwinian” assumption that “survival of the fittest” alone shapes the natural world.

How might Darwin’s two alternative mechanisms show up in the economic world? The “Law of Battle” evokes vast advertising campaigns, often misleading, wasteful and ineffective. Or legal battles over patents and copyrights. But, like the giant horns on a bull elk, blowing money on such activities could signal corporate “fitness.” What about a “Taste for the Beautiful”? That evokes monumental, luxurious corporate headquarters, private planes, eye-popping salaries and other perks for corporate management. Do such features aid or hinder corporate profitability? The Wall Street Journal and the Financial Times overflow with accounts of executives pursuing their self-interest at the expense of the bottom line—even when the value of their stock is falling. Corporations are of course a modern invention; a few generations ago, when businesses were mostly run by families, it would have been laughable to deem the “conspicuous consumption” of wealthy owners as profit-maximizing behavior.

The same fallacy underlies both the theory of “survival of the fittest” and the theory of “cutthroat competition”. That’s the assumption that living species and economic organizations eternally teeter on the razor edge of survival. Put like that, it’s obviously nonsense. In the natural world, saying that a species occupies an ecological “niche” suggests there’s a particular location in which it has enough of an advantage to thrive in good times and survive in bad ones. That location might be a zebra’s gut for botfly larvae or New York City for Norway rats. Businesses have niches too: spots where they enjoy a little—or a lot—of monopoly power. Sr. Perez’s corner bodega enjoys a bit of monopoly power by being the most convenient shopping location at the most convenient hours in the immediate neighborhood. At the other end of the scale, there’s Exxon-Mobil. Monopoly can provide Sr. Perez a small cushion when bad weather keeps customers indoors; international monopoly provides a tempting slush fund for Exxon execs.

Prum reminds us we need to challenge rigid doctrines and follow Darwin’s open-minded investigation of the natural or economic world around us. (Of course, if the central problem of capitalism is monopoly instead of cutthroat competition, we must look for alternative solutions.)

* By “fitness”, Darwin meant adaptation to the environment, or ability to survive—an objective characteristic. Modern evolutionary scientists, to Prum’s infinite annoyance, have redefined “fitness” as relative success in passing on one’s genes. This circular definition—success as its own measure—makes Darwin’s ideas of sexual selection meaningless.