Levels of inequality have changed dramatically during the course of human evolution: from the social hierarchies of our great ape ancestors to egalitarian small-scale societies of hunter-gatherers, and then to large-scale hierarchical societies with great inequities in the distribution of power, status, and wealth. The Axial Age (c.800–200 BCE) introduced another notable transformation in the evolution of inequality, starting a move towards greater egalitarianism that has been continuing to the present. The resulting trajectory of inequality looks like a Z, and for this reason some time ago I proposed that we call it the Z-curve:

Recently David Graeber and David Wengrow questioned an important part of this story:

For centuries, we have been telling ourselves a simple story about the origins of social inequality. For most of their history, humans lived in tiny egalitarian bands of hunter-gatherers. Then came farming, which brought with it private property, and then the rise of cities which meant the emergence of civilisation properly speaking. … There is a fundamental problem with this narrative: it isn’t true.

For a general critique of their ideas see my previous post. I don’t disagree with everything they say (for example, the relationship between the adoption of agriculture and the rise of large-scale complex societies is indeed more complex than is usually portrayed). But the central idea in their essay, that there was no transition from egalitarian Pleistocene foragers to inegalitarian early states is wrong.

To be sure, when we talk about forager egalitarianism, nobody thinks that they were completely, absolutely equal. Of course, there were differences between men and women, children and adults; in physical prowess and in social influence. When we talk about the evolution of human inequality in the long run, we mean changes in relative levels of it.

Second, and perhaps more important, forager egalitarianism was not simply a result of foragers having fewer possessions than a typical person has today. The reason we say that foragers were fiercely egalitarian is because they practiced reverse dominance hierarchy. The key thinker here is Chris Boehm (whom G&W never mention). The goal of reverse hierarchy is to restrain physically powerful and aggressive men. Foraging societies use a variety of social mechanisms to prevent such “upstarts” (as Boehm calls them) from bullying everybody, ranging from gossip and ridicule to expulsion and even capital punishment.

How do we know that this is an accurate representation of typical social arrangements during the Pleistocene? A good summary of the argument is given by the anthropologist Camilla Power in her own critique of G&W.

Camilla Power is a self-described radical feminist, but as we shall see below, her political views do not interfere with her scholarship. However, as her focus is primarily on sex and gender, her perspective needs to be supplemented by a few other ideas/facts relevant to the broader issue of forager egalitarianism.

Here are the main points she makes (I will again quote large chunks of her text, as I did in the previous post).

Cooperative child-raising and menopause

In Mothers and Others, the most important book on human evolution published this century, the outstanding Darwinian feminist Sarah Hrdy … presents a straightforward argument. We do babysitting in all human societies, mothers being happy to hand over their offspring for others to look after temporarily. African hunter-gatherers are the champions of this collective form of childcare, indicating that it was routine in our heritage. In stark contrast, great ape mothers – chimpanzees, bonobos, gorillas and orang utans – do not let their babies go. Because of the risks of harm to their infants, they are hyperpossessive and protective, not daring to take the chance. … Our foremothers must have been living close to trusted female relatives, the most reliable in the first place being a young mother’s own mother. This ‘grandmother hypothesis’ has been used to explain our long post-reproductive lifespans – the evolution of menopause. Hrdy explores how multi-parental care shaped the evolution of our species’ unique psychological nature. While cooperative childcare may start with the mother-daughter relationship, bonding with grandchildren quickly leads to the involvement of aunts, sisters, older daughters and other trusted relatives.

Unlike female chimpanzee, who disperse to other troops upon reaching sexual maturity, women in foraging societies stay with their native bands, argues Power. As a result, these women are embedded in thick support networks, not only of female relatives, but also of related males (their brothers, their mother’s brothers). This gives women social power to control powerful and aggressive bullies.

Concealed ovulation

Women have evolved a sexual physiology which can be described as levelling and time-wasting. Why? Because if a hominin female really needs extra energy for her hungry offspring, better to give reproductive rewards to males who will hang around and do something useful for those offspring. Our reproductive signals make life hard for males who want to identify fertile females, monopolise the fertile moment and then move on to the next one (a classic strategy for dominant male apes). We have concealed and unpredictable ovulation. … For a dominant male trying to manage a harem of females this is disastrous. While he is guessing about the possible fertility of one cycling female, he has to stay with her, and is missing other opportunities. Meanwhile, other males will be attending to those other sexually receptive females. Continuous sexual receptivity spreads the reproductive opportunities around many males, hence is levelling from an evolutionary perspective.

In chimps and gorillas (and probably in our Great Ape ancestors) some males enjoy huge mating success, and others none. For example, in gorillas dominant silverbacks jealously guard harems of females, which means that most male gorillas don’t get to mate. Male reproductive success in Pleistocene foragers was probably much more equitably distributed, and concealed ovulation and continuous sexual receptivity in females played a big role in this shift. Of course, once early centralized societies arose, the alpha males were able to put together huge harems maintained by coercive power (for example, using eunuchs to guard their wives). Again we see the zigs and zags of inegalitarianism in human social evolution.

Source

Huge energetically demanding brains

The most salient feature of our anatomy distinguishing us from other apes is the extraordinary size of our brains. … Brain tissue is very expensive in terms of energy requirements. Doing the whole job by themselves, great ape mothers are constrained in the amount of energy they can provide to offspring and so apes cannot expand brains above what is known as a ‘gray ceiling’ (600 cc). Our ancestors smashed through this ceiling some 1.5-2 million years ago with the emergence of Homo erectus, who had brains more than twice the volume of chimps today. This tells us that cooperative childcare was already part of Homo erectus society.

This is an interesting idea and I am not sure I entirely buy it. In any case, this account is incomplete without bringing in another important factor: the radical change of diet, which occurred two, or more, million years ago. When our ancestors moved to the savannas they started consuming much greater quantities of animal protein and fat, which they obtained by scavenging and (later) hunting. Somewhat later they started processing food for easier digestibility. Anthropologists like Richard Wrangham make a strong argument that cooking food over fire was what made us human. But cooking is not only treating food with heat—roasting, baking, boiling, stewing, frying in oil, sautéing, etc. In a more general sense it also includes chopping, slicing, pounding, grinding, leaching, marinading, smoking, salting, drying—and seasoning. Processing food in this fashion “externalizes” digestion. The key book to read on this topic is Joe Henrich’s The Secret of Our Success (see my review How Social Norms Are Like Chili Peppers). It was this dietary change that made possible our huge and energetically expensive brains.

Any tendency to male dominance and strategic control of females would have obstructed these unprecedented increases of brain size. While there must have been variability in the degree of dominance or egalitarianism among human groups, we can be confident that those populations where male dominance, sexual conflict and infanticide risks remained high were not the ones who became our ancestors. Our forebears were the ones who somehow solved the problem of great ape male dominance, instead harnessing males into routine support of these extraordinarily large-brained offspring.

In other words, inegalitarian groups were weeded out by evolution working at the level of groups.

Mutual mindreading

Perhaps the hallmark of our egalitarian nature is the design of our eyes. We are the only one of well over 200 primate species to have evolved eyes with an elongated shape and a bright white sclera background to a dark iris. Known as ‘cooperative eyes’, they invite anyone we interact with to see easily what we are looking at. By contrast, great apes have round, dark eyes, making it very difficult to judge their eye direction. Like mafia dons wearing sunglasses, they watch other animal’s moves intently, but disguise their thoughts from others. This suits a primate world of Machiavellian competition. Our eyes are adapted for mutual mindreading, also called intersubjectivity; our closest relatives block this off. To look into each other’s eyes, asking ‘can you see what I see?’ and ‘are you thinking what I am thinking?’ is completely natural to us, from an early age. Staring into the eyes of other primate species is taken as a threat. This tells us immediately that we evolved along a different path from our closest primate relatives.

This is a great example of another trait that distinguishes humans from our Great Ape relatives, and helps to explain our uniquely cooperative species. I use it in my course, Cultural Evolution, and it is a revelation to my students. By the way, as far as I know there is apparently only one other animal that can read humans’ eyes — dogs (but not wolves).

Symbolism and language

Over fifty years ago, leading US anthropologist Marshall Sahlins made a revealing comparison of nonhuman primates against human hunter-gatherers. Noting egalitarianism as a key difference, he saw culture as ‘the oldest “equalizer”. Among animals capable of symbolic communication’ he said, ‘the weak can collectively connive to overthrow the strong.’ We can reverse the arrow of causality here. Because among Machiavellian and counterdominant humans weaker individuals can connive to overthrow the strong, we are animals capable of symbolic communication. Only in such conditions is language likely to emerge. The strong have no need of words; they have more direct physical means of persuasion.

Ability to communicate effectively and plan collective action is absolutely the key to controlling upstarts. Obviously, gossip and ridicule become much more effective with language. But harsher forms of control, such as expulsion and capital punishment also need extensive planning and seamless execution. A powerful and aggressive upstart is too intimidating and dangerous. The whole band needs to agree on how to get rid of him in a safe manner. His relatives might need to be persuaded to join the punishing detail, or at least to step aside. Language is key to all of this.

Projectile weapons

One other characteristic that distinguished early humans from other great apes, and which Powell doesn’t address, is our uncanny ability to use projectile weapons: starting with stones, then throwing spears, and later slings and bows. The key authors here are Herbert Gintis (whom Power cites in another context) and Carel van Schaik. I discuss this story in Chapter 5, “God Made Men, but Sam Colt Made Them Equal” of Ultrasociety. The idea is simple. Confronting a powerful and angry upstart with hand-held weapons is dangerous and inefficient. It is much better to get a coalition of ten or more people to shoot the bully from distance.

Execution Group, Remigia, Castellón, Spain

Summing up

Women’s bodies evolved over a million years to favour the ‘one woman, one penis’ principle, rewarding males who were willing to share and invest over those who competed for extra females, at the expense of investment. But as we became more Machiavellian in our strategies, so did would-be alpha males. The final steep rise in brain size up to the emergence of modern humans likely reflects an arms race of Machiavellian strategies between the sexes. As brain sizes increased, mothers needed more regular and reliable contributions from male partners. In African hunter-gatherers this has become a fixed pattern known by anthropologists as ‘bride-service’. A man’s sexual access depends on his success in provisioning and surrendering on demand any game or honey he gets to the family of his bride – mainly his mother-in-law who is effectively his boss. Where women are living with their mothers, this makes it almost impossible for a man to dominate by controlling distribution of food. The problem for early modern human females as they came under the maximum stress of increased brain size would be with males who tried to get away with sex without bride-service. To deal with this threat, mothers of costly offspring extended their alliances to include just about everyone against the potential alpha. Men who were relatives of mothers (brothers or mother’s brothers) would support those females. In addition, men who willingly invested in offspring would have interests directly opposed to the would-be alpha, who undermined their reproductive efforts. This pits a whole community as a coalition against a would-be dominant individual.

What I find particularly compelling about Power’s argument is that it is explicitly evolutionary. She not only uses a variety of data to infer the egalitarianism in Pleistocene foragers, she explains the evolutionary mechanisms that made human societies more equitable, and maintained equity. This is quite unlike G&W. In fact, a disdain for evolution is one of Power’s points of critique against the G&W piece:

As an American cultural anthropologist, Graeber comes from a tradition which regards Darwinism with distrust, viewing it as a Trojan horse for capitalist ideology. But the funny thing is that sociobiology, evolutionary ecology, or whatever you want to call it (it keeps changing name because social and cultural scientists are so rude about it) has taken an extraordinary feminist turn this century. The strategies of females have now become central to models of human origins. Forget ‘man the hunter’, it’s hardworking grandmothers, babysitting apes, children with more than one daddy, who are the new Darwinian heroes. Source

I will end my review with this final quote: