Ron Bailey’s latest Reason column focuses on a study in Nature I’d meant to link a couple weeks back purporting to find a “Robin Hood” impulse in a series of behavior experiments: Subjects randomly allotted varying sums of money, without any prospect of reciprocation or retaliation, were willing to spend their own money to raise the amounts given to “poorer” subjects and (to my mind more interestingly–and pointlessly) reduce the amount the “richer” ones received. In the latter case, as I understand the setup, they weren’t even “robbing from the rich to give to the poor”—they were robbing from the rich and, in effect, burning the money.

It probably bears saying right off the bat that I would be more than a little wary about generalizing from the behavior of 120 U.C. Davis students to some sweeping human tendency. Why researchers would jump to attribute this to a hardwired disposition rather than culture is mystifying. Still, I find the result less surprising than Ron, who writes:

It’s hard to see how an inborn drive could arise in Pleistocene hunter gatherers such that people spend their scarce resources to reduce other people’s resources promotes either individual or group survival.

But it’s less hard if you’ve read Christopher Boehm’s excellent study Hierarchy in the Forest. Boehm finds that, in contrast to the rigidly hierarchical societies of our nearest primate relatives, nomadic hunter-gatherer bands typically exhibit high levels of egalitarianism, as evidenced by strong norms in favor of food-sharing (especially in the case of large “windfall” gains) and the ridicule or shunning of “upstarts” perceived as having gotten too big for their loincloths. Importantly, though, Boehm characterizes this not as an anarchic absence of hierarchy, but as a “reverse dominance hierarchy”: Group members are not just happily equal in the absence of dominant individuals, but rather must work to collectively dominate such potential dominators. In effect, the group as a whole becomes the alpha male.

So, what’s going on here? A couple factors to bear in mind. It is now common—indeed, seems almost “natural”—to associate egalitarianism with “collectivism” or “communitarianism” and, conversely, to see “individualism” as going hand-in-hand with tolerance for relatively high levels of inequality in wealth and income. This is, when you think about it, highly artificial: for most of human history (or, more precisely, human pre-history), there would have been little or no disconnect between wealth, status, and power over others. Someone strong and quick enough to acquire the largest share of food was likely to be strong and quick enough to impose his will on others as well. What Boehm found, then, was that members of hunter-gatherer bands were, in one sense, fiercely individualistic, and highly protective of their own autonomy. But this entailed working with others to scrupulously limit and check the power of others. In such bands, Boehm observes, the leader is frequently the poorest member of the band. It is, when you think about it, an incredible anomaly that Bill Gates, for all his status and vastly disproportionate wealth, cannot march into my home, cart off my stuff, boss me around, and demand sex with all the women in the house.

Ah yes, sex. Recall, after all, that for all the potential shared gains from competitive cooperation, one dimension of inequality is always zero-sum from an evolutionary perspective: Reproduction. Anything that enhances the reproductive fitness of one male, by definition, reduces that of his peers. If the proportion of genome A rises from one generation to the next, the proportion of the others has to decline, even if the total number of organisms is growing. To put it crudely, castrating all your sexual competitors is as sound an evolutionary strategy as increasing your own attractiveness. So if a number of Betas can restrict the advantages of a prospective Alpha, this too will increase their relative reproductive success.

So why do we find this pattern among humans and not other primates? Boehm suggests a few possibilities. Primitive technology is one. Hobbes believed that his social contract would be stabilized by one all-important form of natural equality among human beings: Even the weakest individual was capable of killing the strongest. Yet this is plainly untrue in hand-to-hand combat, even if one person has the element of surprise on his side. Hobbes’ inequality depends on weaponry: A domineering group member, however physically strong, can be quickly brought down at some distance by a spear or arrow if caught unawares. Language is another key component, enabling greater collaboration among group members against a potential upstart, and more rapid sharing of information about upstart behavior. Over hundreds of generations, these social facts themselves become part of the selection environment, shaping the human genome. The egalitarian impulse, then, is cemented by a kind of collective self-domestication. We go from homo homini lupus to homo homini canis.