First, before I get to the three theories, I must address this question: Is it true that hunter-gatherers were peaceful egalitarians? The answer is yes.
During the twentieth century, anthropologists discovered and studied dozens of different hunter-gatherer societies, in various remote parts of the world, who had been nearly untouched by modern influences. Wherever they were found--in Africa, Asia, South America, or elsewhere; in deserts or in jungles--these societies had many characteristics in common. The people lived in small bands, of about 20 to 50 persons (including children) per band, who moved from camp to camp within a relatively circumscribed area to follow the available game and edible vegetation. The people had friends and relatives in neighboring bands and maintained peaceful relationships with neighboring bands. Warfare was unknown to most of these societies, and where it was known it was the result of interactions with warlike groups of people who were not hunter-gatherers. In each of these societies, the dominant cultural ethos was one that emphasized individual autonomy, non-directive childrearing methods, nonviolence, sharing, cooperation, and consensual decision-making. Their core value, which underlay all of the rest, was that of the equality of individuals.
We citizens of a modern democracy claim to believe in equality, but our sense of equality is not even close that of hunter-gatherers. The hunter-gatherer version of equality meant that each person was equally entitled to food, regardless of his or her ability to find or capture it; so food was shared. It meant that nobody had more wealth than anyone else; so all material goods were shared. It meant that nobody had the right to tell others what to do; so each person made his or her own decisions. It meant that even parents didn't have the right to order their children around; hence the non-directive childrearing methods that I have discussed in previous posts. It meant that group decisions had to be made by consensus; hence no boss, "big man," or chief.
If just one anthropologist had reported all this, we might assume that he or she was a starry-eyed romantic who was seeing things that weren't really there, or was a liar. But many anthropologists, of all political stripes, regarding many different hunter-gatherer cultures, have told the same general story. There are some variations from culture to culture, of course, and not all of the cultures are quite as peaceful and fully egalitarian as others, but the generalities are the same. One anthropologist after another has been amazed by the degree of equality, individual autonomy, indulgent treatment of children, cooperation, and sharing in the hunter-gatherer culture that he or she studied. When you read about "warlike primitive tribes," or about indigenous people who held slaves, or about tribal cultures with gross inequalities between men and women, you are not reading about band hunter-gatherers.
Even today some people who should know better confuse primitive agricultural societies with hunter-gatherer societies and argue, from such confused evidence, that hunter-gatherers were violent and warlike. For example, one society often referred to in this mistaken way is that of the Yanomami, of South America's Amazon, made famous by Napoleon Chagnon in his book subtitled The fierce people. Chagnon tried to portray the Yanomami as representative of our pre-agricultural ancestors. But Chagnon knew well that the Yanomami were not hunter-gatherers and had not been for centuries. They did some hunting and gathering, but got the great majority of their calories from bananas and plantains, which they planted, cultivated, and harvested. Moreover, far from being untouched by modern cultures, these people had been repeatedly subjected to slave raids and genocide at the hands of truly vicious Spanish, Dutch, and Portuguese invaders. No wonder they had become a bit "fierce" themselves.
The hunter-gatherer way of life, unlike the agricultural way of life that followed it, apparently depended on intense cooperation and sharing, backed up by a strong egalitarian ethos; so, hunter-gatherers everywhere found ways to maintain a strong egalitarian ethos. Now, back to the main question of this post. How did hunter-gatherers maintain their egalitarian ways? Here are the three theories, which I think are complementary to one another and all correct.
Theory 1: Hunter-gatherers practiced a system of "reverse dominance" that prevented anyone from assuming power over others.
The writings of anthropologists make it clear that hunter-gatherers were not passively egalitarian; they were actively so. Indeed, in the words of anthropologist Richard Lee, they were fiercely egalitarian. They would not tolerate anyone's boasting, or putting on airs, or trying to lord it over others. Their first line of defense was ridicule. If anyone--especially if some young man--attempted to act better than others or failed to show proper humility in daily life, the rest of the group, especially the elders, would make fun of that person until proper humility was shown.
One regular practice of the group that Lee studied was that of "insulting the meat." Whenever a hunter brought back a fat antelope or other prized game item to be shared with the band, the hunter had to express proper humility by talking about how skinny and worthless it was. If he failed to do that (which happened rarely), others would do it for him and make fun of him in the process. When Lee asked one of the elders of the group about this practice, the response he received was the following: "When a young man kills much meat, he comes to think of himself as a big man, and he thinks of the rest of us as his inferiors. We can't accept this. We refuse one who boasts, for someday his pride will make him kill somebody. So we always speak of his meat as worthless. In this way we cool his heart and make him gentle."
On the basis of such observations, Christopher Boehm proposed the theory that hunter-gatherers maintained equality through a practice that he labeled reverse dominance. In a standard dominance hierarchy--as can be seen in all of our ape relatives (yes, even in bonobos)--a few individuals dominate the many. In a system of reverse dominance, however, the many act in unison to deflate the ego of anyone who tries, even in an incipient way, to dominate them.
According to Boehm, hunter-gatherers are continuously vigilant to transgressions against the egalitarian ethos. Someone who boasts, or fails to share, or in any way seems to think that he (or she, but usually it's a he) is better than others is put in his place through teasing, which stops once the person stops the offensive behavior. If teasing doesn't work, the next step is shunning. The band acts as if the offending person doesn't exist. That almost always works. Imagine what it is like to be completely ignored by the very people on whom your life depends. No human being can live for long alone. The person either comes around, or he moves away and joins another band, where he'd better shape up or the same thing will happen again. In his 1999 book, Hierarchy in the Forest, Boehm presents very compelling evidence for his reverse dominance theory.
Theory 2: Hunter-gathers maintained equality by nurturing the playful side of their human nature, and play promotes equality.
This is my own theory, which I introduced two years ago in an article in the American Journal of Play. I will not go into detail about it here, because I have presented bits of the theory in other posts (see, for example, my post of June 11, 2009). Briefly, however, the theory is this. Hunter-gatherers maintained their egalitarian ethos by cultivating the playful side of their human nature.
Social play--that is, play involving more than one player--is necessarily egalitarian. It always requires a suspension of aggression and dominance along with a heightened sensitivity to the needs and desires of the other players. Players may recognize that one playmate is better at the played activity than are others, but that recognition must not lead the one who is better to lord it over the others.
This is true for play among animals as well as for that among humans. For example, when two young monkeys of different size and strength engage in a play fight, the stronger one deliberately self-handicaps, avoids actions that would frighten or hurt the playmate, and sends repeated play signals that are understood as signs of non-aggression. That is what makes the activity a play fight instead of a real fight. If the stronger animal failed to behave in these ways, the weaker one would feel threatened and flee, and the play would end. The drive to play, therefore, requires suppression of the drive to dominate.
My theory, then, is that hunter-gatherers suppressed the tendency to dominate and promoted egalitarian sharing and cooperation by deliberately fostering a playful attitude in essentially all of their social activities. Our capacity for play, which we inherited from our mammalian ancestors, is the natural, evolved capacity that best counters our capacity to dominate, which we also inherited from our mammalian ancestors.
My play theory of hunter-gather equality is based largely on evidence, gleaned from analysis of the anthropological literature, that play permeated the social lives of hunter-gatherers--more so than is the case for any known, long-lasting post-hunter-gatherer cultures. Their hunting and gathering were playful; their religious beliefs and practices were playful; their practices of dividing meat and of sharing goods outside of the band as well as inside of the band were playful; and even their most common methods of punishing offenders within their group (through humor and ridicule) had a playful element. By infusing essentially all of their activities with play, hunter-gatherers kept themselves in the kind of mood that most strongly, by evolutionary design, counters the drive to dominate others.
Theory 3: Hunter-gatherers maintained their ethos of equality through their childrearing practices, which engendered feelings of trust and acceptance in each new generation.
As I have explained in a previous post, hunter-gatherers employed a style of parenting that others have referred to as "permissive" or "indulgent," but which I prefer to call "trusting." They trusted infants' and children's instincts, and so they allowed infants to decide, for example, when to nurse or not nurse and allowed children to educate themselves through their own self-directed play and exploration. They did not physically punish children and rarely criticized them. One researcher who suggested that the moral character of hunter-gatherers comes from their kindly child-raising methods is Elizabeth Marshall Thomas, who was among the first to study the Ju/'hoansi of Africa's Kalahari Desert. Here is what she had to say about the parenting she observed:
"Ju/'hoan children very rarely cried, probably because they had little to cry about. No child was ever yelled at or slapped or physically punished, and few were even scolded. Most never heard a discouraging word until they were approaching adolescence, and even then the reprimand, if it really was a reprimand, was delivered in a soft voice. ... We are sometimes told that children who are treated so kindly become spoiled, but this is because those who hold that opinion have no idea how successful such measures can be. Free from frustration or anxiety, sunny and cooperative, the children were every parent's dream. No culture can ever have raised better, more intelligent, more likable, more confident children."
One esteemed contemporary researcher who has implicitly if not explicitly supported the parenting theory of hunter-gatherer moral development is fellow PT blogger Darcia Narvaez, author of the blog Moral Landscapes. It is difficult to prove with empirical evidence that the kindly, trustful parenting of hunter-gatherers promotes development of people who treat one another kindly and who eschew aggression, but the theory makes intuitive sense. It makes sense that infants and children who are themselves trusted and treated well from the beginning would grow up to trust others and treat them well and would feel little or no need to dominate others in order to get their needs met.
The childrearing theory overlaps with my play theory, because hunter-gatherers allowed their children, including teenagers, to play essentially from dawn to dusk. The children grew up believing that life is play and then went on to conduct esssentially all of their adult tasks in a playful mood--the mood that counters the drive to dominate.
In sum, my argument here is that the lessons we have to learn from hunter-gatherers are not about our genes but about our culture. Our species clearly has the genetic potential to be peaceful and egalitarian, on the one hand, or to be warlike and despotic, on the other, or anything in between. If the three theories I've described here are correct, and if we truly believe in the values of equality and peace and want them to reign once again as the norm for human beings, then we need to (a) find ways to deflate the egos, rather than support the egos, of the despots, bullies, and braggarts among us; (b) make our ways of life more playful; and (c) raise our children in kindly, trusting ways.
And now, I hope to hear from you in the comments and questions space below. I read all comments with the intent of learning from them, and I try to respond to all serious questions. I prefer if you put your comments and questions here rather than in a private email to me. By putting them here, you share with other readers, not just me. -- Peace be with you.
See new book, Free to Learn
 Salamone, F. A. (1997). The Yanomami and their interpreters: Fierce people or fierce interpreters? Lanham, Maryland: University Press of America.
 Lee, R. B. (1988). Reflections on primitive communism. In T. Ingold, D. Riches, & J. Woodburn (Eds), Hunters and gatherers 1, 252-268 Oxford: Berg.
 Gray, P. (2009). Play as a foundation for hunter-gatherer social existence. American Journal of Play, 1, 476-522.
 Thomas, E. M. (2006). The old way. New York: Farrar, Straus & Giroux. p 198-199.