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In 1802 P. Huber related the concept of dominance to the social behavior of bumblebees. Almost 100 years later, Thorleif Schjelderup-Ebbe (1935) wrote about pecking orders in chickens, describing a hierarchy in which the top-ranking chicken could peck all the others with impunity and the second-ranking could do the same thing to all except the first one, down to the last-ranking bird, which was pecked by all and could peck none in return. The idea of dominance was applied to explain the directionality of aggressive behavior in animals that live socially and was defined as a relationship learned through previous experience.


Ray Carpenter applied the concept to nonhuman primates and considered it a universal principle that shapes all primate social organizations (1954). Interest quickly was focused on individual attributes that might account for the achievement of high rank and its consequences. Size and strength may contribute, but Masao Kawai and Syunzo Kawamura (1958) and Bernard Chapais (1992) demonstrated that social skills and alliances are far more important in determining the dominance positions of monkeys. Irwin Bernstein and colleagues showed that dominance ranks have meaning only in a specific social context (1980). In different groups individual ranks can be reversed, and the highest-ranking individual in one group can be the lowest-ranking in another. Dominance thus is not an attribute that can be studied in an isolated individual.

The functions of dominance were speculated to relate to instrumental aggression, a process in which aggression is used to gain something at the expense of a rival. Dominant individuals were expected to have priority of access to food, mates, and other resources. However, the existence of mixed evolutionarily stable strategies was interpreted to mean that alternative means might obscure the expected correlation between rank and resources. If dominance meant access to incentives, it was speculated that individuals would strive actively for high rank, but William Mason and Sally Mendoza found little evidence that primates fight specifically to attain rank (1993). Moreover, empirical studies of genetic fitness and high rank have not always demonstrated the expected correlation. Market theories that suggest that animals should perform favors for those of high rank in exchange for services such as agonistic aid and tolerance also have received mixed support. Although there are good correlations between grooming and dominance in some groups, the tendency for kin or other close associates to both groom and aid one another can override any tendency for lower-ranking animals to groom higher-ranking animals.


The search for biological correlates of dominance rank revealed that whereas some characteristics may contribute to the attainment of high rank, others may follow as a consequence of achieving that rank. Robert Rose and colleagues initially assumed that the correlation between male testosterone levels and dominance suggests that hormones contribute to dominance (1971) but later found that recent histories of winning or losing a fight account for profound changes in testosterone levels. The correlation with dominance pertained only immediately after fighting had established or changed dominance positions. Robert M. Sapolsky reported that cortisol levels were lower in dominant individuals, but only when the group was in a period of social stability (1984). Hormone levels both influence social interactions and are a result of those interactions.

Since dominance relationships are often linear, the first position is called alpha and the last is called omega. The alpha animal can be expected to be the leader of a primate group, but high agonistic rank does not lead routinely to leadership of group movements or other activities. The alpha individual may be assumed to be integral to the defense of the group against external and internal threats, but the control role often is played by individuals other than the alpha. In macaque and baboon societies sexual dimorphism in body size, canine size, and other features may contribute to a male becoming the alpha animal in the group, but sometimes a female may outrank all the males. Among the lemurs females routinely assume the alpha position. Nonetheless, with the original assumption that males would be the highest-ranking individuals, investigators asked whether females also have an alpha with special characteristics, as is assumed for alpha males. Of course this required separating the sexes in determining relative ranks, and some researchers went so far as to suggest that all adult males outrank all adult females. Whereas this occasionally may be true for some species, it is far from a general rule.

The focus on biological correlates of alphaness led to considerations of the evolutionary consequences of natural selection on behavior. If males were selected on the basis of their ability to defeat other males to obtain access to females (Charles Darwins intrasexual selection), larger, more aggressive males would have higher genetic fitness. Aggression was expected in males, whereas females were expected to be more passive and even coy, inciting males to demonstrate their superior prowess. Male aggression also could be directed against females to coerce mating (reducing the effect of Darwins second principle of sexual selection: epigamic selection, or female choice). With a long history of natural selection favoring aggressive males that fought other males and coerced females, one would expect strong differences in the aggressiveness of the sexes, and such differences were assumed and supported by the more extreme consequences of male aggression. This, however, is a poor indicator of differential initiation, participation, and duration of aggression. Because of different anatomic capabilities, aggression by females may take forms different from those of male aggression and inflict less damage, but does this mean that verbal aggression or social ostracism (presumed to be more common in human females) is any less aggressive than physical attacks? In many species the frequency and duration of female aggression exceed those of males, although the consequences of male aggression are usually more severe.

If, however, evolution has favored males that are highly aggressive and engage in sexual coercion, it is not surprising that males, with their correlated higher levels of male hormones, are more aggressive than females. (The relationship with male testosterone is widely assumed and castration often is recommended to reduce aggression in animals and human males, but there is little proof that there is a direct correlation between testosterone levels and aggression.) If male aggression is natural, Richard Wrangham and Dale Peterson argued in 1996, males are possessed by demons that drive their behavior. They fight and copulate at every opportunity because evolution has shaped them to do that. If natural selection is responsible, should they be blamed, or should researchers be more accepting of male aggression and sexual coercion? Does this excuse the inexcusable? Are people really programmed by their hormones and heredity so that free will has little influence on typical sex behavior? Is sexual dimorphism proof that males have greater physical fighting abilities so that they can defeat other males in contests for mating, or is it possible that other factors promote a sexual division of labor that favors larger size and fighting ability in males and/or smaller size in females? Sexual dimorphism could as easily be due to differences in the social roles of males and females with regard to group defense against predators, rival groups, or other sources of potential disturbance or even to differences in foraging patterns that reduce competition for food within a group. Plausibility seems the only argument for favoring one interpretation over another, and sexual dimorphism often is assumed to be proof of male mating patterns.


The application of speculations about nonhuman primate behavior to the understanding of the human condition is fraught with peril. Alphaness is more an artifact of peoples ability to count than a matter of biology. Linear hierarchies are appealing, but the game paper, scissors, rock also can describe dominance. Researchers see an entire group, but animals may be more self-centered and see only their individual relationships with the members of the group. They may not have abstract concepts of group organization.

Dominance in human groups may be pronounced in institutions with a rank hierarchy such as the military; an alpha may be suggested when groups have a clear leader and the others are all more or less equal followers, but some human groupings do not show structures that suggest that individuals have histories of coercive relationships that lead to recognized superiors. Christopher Boehm suggested that many human social structures have specific mechanisms that preclude the development of alpha positions (1994). The existence of leadership does not require aggression or a history of aggressive contests, although that may occur in some circumstances. Superior reproductive success can correlate with high social status, but it need not. (Genetic fitness is defined by the number of replicates of an individuals genes that show up in a future generation compared to the average individual in the populationroughly equivalent to the number of grandchildren or great grandchildren that one has. For the last several decades there has been an inverse relationship between economic status and genetic fitness.) Presumed correlates of dominance or alpha status cannot be construed as evidence that alpha status exists.

If the term alpha-male is used to indicate a male that uses social position to obtain more mating or power over others, surely females might do the same and there would be alpha females. These concepts are a far cry from the origins of the term in animal behavior, where alpha was used to designate the individual that could aggress against others without fear of retaliation. Whether dominance leads to increased mating or access to resources is an empirical question, and the data do not always support such hypotheses. Thus, the relationships among dominance rank, genetic fitness, and status are empirical questions with regard to humans as well, and one cannot assume that success in any one area implies success in the others. Researchers may describe alpha individuals of either sex or of a group, but they should describe data and not assume data on the basis of theory.

SEE ALSO Aggression; Hierarchy; Men; Military; Organization Theory; Social Dominance Orientation; Sociobiology; Violence


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Irwin S. Bernstein