We human beings are hierarchical animals. Always and everywhere, we have ranked ourselves in comparison with others of our species. While many contemporary social scientists seem to believe that equality is our default status, all societies, ranging from hunter-gatherer communities to modern techno-commercial civilizations, have sorted people by their relative power.

Far from inequality having been imposed upon us by unscrupulous elites, we all participate in drawing invidious distinctions. To put the matter baldly: all of us seek to be winners. And all of us hate being losers. Yet if some of us are to win, others of us must lose. This is a nasty truth that is recognized even by little leaguers who are not fooled when adults insist on awarding trophies to all players on the grounds that participating is tantamount to winning.

Nevertheless, the sorts of hierarchies different societies have constructed vary widely. These include the modest disparities of hunting bands, the more emphatic distinctions of Big Men horticultural communities, the huge social distances imposed by ancient agricultural empires, the almost species-like categories enforced by caste societies, as well as the less onerous pecking orders that characterize social class based cultures-such as our own.

Any overarching theory about how hierarchies operate must therefore explain these discrepancies. If it is to offer valid hypotheses regarding the mechanisms through which differences in status are constructed and maintained, it must elucidate why they occur. Thus, conceptual schemes that assume the root cause of inequality lies in the extraordinary selfishness of a small number of oppressors need to provide evidence of their unique egoism. They cannot merely blame the rapaciousness of capitalists or some other set of oppressors.

In fact, many recent sociological speculations about hierarchy are exercises in moralistic posturing. Often neo-Marxist in conception, they assume that once property-owning villains are deprived of their unearned advantages, fairness and parity will arise of their own accord. How this is supposed to happen is never fully explicated, it is merely presupposed as an inevitable consequence of the arrow of history.

Genuine science must do better. It has to suggest causal mechanisms that are capable of being disconfirmed by empirical observations. Rather than incessantly engaging in studies designed to prove that inequalities exist under the current social conditions, it must dig deeper to investigate the underlying causes of these disparities. This is the task that my book Human Hierarchies: A General Theory has set for itself.

Dirck Jacobsz, Group Portrait of the Amsterdam Shooting Corporation, 1561, Oil on panel, 91 x 185 cm, The Hermitage, St. Petersburg

I begin with the observation that hierarchy is not exclusive to human societies. Many other social animals also engage in ranking themselves. Moreover, I argue that the resulting structures are functional. They enable groups of individuals to coordinate their activities such that they improve the chances of collective survival-if not that of all their members.

I go on to contend that the central mechanism for establishing differences in relative power is "tests of strength." Just as rams butt their heads together to determine which is the dominant animal, so people engage in trials to establish who among them is stronger. This by itself, however, would be insufficient to create stable ranking systems. It is also necessary that the losers back down after they have lost and that the winners acquire a "reputation" for potency that dissuades other animals from launching immediate challenges. The differences that emerge from this process are further reinforced by displays of dominance and submission that subsequently confirm the standing of particular individuals.

As it happens, the sorts of strength utilized to institute human hierarchies are more variable than among other social animals. Physical power matters among people, but because we are social generalists other abilities do as well. Thus, we also defer to greater intelligence, beauty, athleticism, military skill, spiritual intensity, and economic success. Which count most depends on the environmental and social conditions in which they are embedded. Nonetheless, it is possible for multiple hierarchies, based on different criteria, to operate in parallel. In other words, people can be winners based on diverse strengths.

Two other factors that differentiate human hierarchies from those of other animals derive from the size of our communities and the complexity of our interpersonal activities. First, modern societies are far too large for every individual to test his or her strength against every other individual. Such face-to-face comparisons must therefore be supplemented by "symbolic" means. Hence the ways people dress, talk, and comport themselves are all used to provide evidence of relative power. So are the houses in which they live, the automobiles they drive, and the jobs they occupy. This, however, leaves considerable room for deception and manipulation.

Second, we humans do not merely test ourselves against individual others. We also recruit allies with whom to engage in tests against similar collections of collaborators. So important is this tendency to gather and deploy assemblages of associates that we have a name for it. We call it "politics." Most of us consequently acquire statuses that depend upon our standing within groups, as well as from their standing compared with competing groups. The president of the United States is accordingly reckoned to be very powerful, even though he/she may be physically unimpressive.

Taken together these complications make sense of the enormous disparities both within and between groups at particular points in history. What is possible varies a great deal-but it is not infinitely plastic. Who gets to be on top (or the bottom) and how they get there can change. So can the distance from the apex to the sub-basement and the opportunities for social mobility. These are not constants-although the existence of inequality is.

If this is true, then there are limitations on the sorts of reform that are feasible. Simply transferring resources from one group of people to another will not, of itself, eliminate differences in rank. Because hierarchical standing is comparative, people are generally aware of their inferiority or superiority relative to those against whom they measure themselves. Simply building up their egos or bank accounts may not erase disparities in power-if these exist.

It must also be noted that many contemporary organizations are constructed in accord with a particular hierarchical format. They are bureaucratic, which as Max Weber taught us, means they incorporate "hierarchies of authority." Part of what gives such arrangements their stability and precision is that they delegate power in conjunction with role responsibilities. This makes them less arbitrary and more conflict-free than their precursors. While they may be rigid, they are also capable of complexity and sophistication.

Less well appreciated, but growing in significance, are organizations grounded in professionalized authority. Here the comparative power of individuals depends more on their technical expertise and degree of self-motivation. In traditional bureaucracies, bosses make decisions that are imposed on subordinates. In more professionalized organizations, professionals are delegated control of their work product because they can be trusted to exercise competence. This makes these structures less coercive, although it does not eliminate inequalities.

The bottom line is that if human societies are to be modified in directions more people find fulfilling, this can only occur if the nature of human hierarchies is acknowledged and understood. This search is a worthy endeavor to which the social sciences ought apply themselves without committing to a preferred moral outcome.