biosocial female choice theory of social stratification, The
The Biosocial Female Choice Theory of Social Stratification*
ABSTRACT: For decades, the study of social stratification has been dominated by environmental theories. Herein a theory is proposed that contains both biological and sociocultural elements. The theory asserts that most human females, like females of many other mammalian species, have evolved mating preferences biased toward males who are competent in provisioning resources. This female bias is hypothesized to have been naturally selected because females with these biases nearly always have had a reproductive edge over females who lack such a bias. One result of this bias is that human females preferentially mate with males who strive to rise in social status. This, in turn, has favored males who attain or at least strive for high social status, and who advertise and even exaggerate whatever status they already have achieved. At the genetic level, the theory postulates that alleles have accumulated on the human genome that promote social status-striving and achievement to varying degrees. To account for why males are more prone toward status-striving than females, the theory contends that one or more genes on the Y-chromosome interact with genes on the remaining human chromosomes to incline males to gravitate toward social hierarchies and to strive for niches that are relatively high in those hierarchies. Both tested and untested hypotheses are derived from the theory and compared to the empirical evidence currently available.
No topic is more central to sociology, economics, political science, and probably even history than social stratification. At least since the 1960s, two theories have dominated the study of social stratification: functional theory and conflict theory (Lipset, 1976:314; Betz, Davis, and Miller, 1978:399; Blumberg, 1978:vi; Lenski and Lenski, 1982:53; Kerbo, 1983:88; Thio, 1986:210; Short, 1991:90). (A theory in the tradition of Max Weber is sometimes mentioned as forming a third theoretical tradition in the study of social stratification [Grimes, 1991:147; Lopreato and Crippen, 1999:209].)
Functional theory envisions social stratification as a by-product of societal organization. Basically, persons who attain high social status are assumed to possess skills and talents that are most important for the efficient functioning of a particular society (Hall, 1969:298; Rothman, 1993:33). Low wages and minimal prestige are normally relegated to persons possessing the fewest skills and talents that are of value to a society (Davis and Moore, 1945). Overall, functional theorists argue that persons who possess the prized skills and talents move into the most prestigious occupations, and that they along with their family members thereby garner the highest wages and other social rewards.
Conflict theory asserts that groups of people (classes) are in conflict over resources (Klockars, 1980:95). Those classes with the greatest power in a particular society tend to exploit the other classes to the extent possible. Members of the different classes are seen as possessing fairly distinct relationships to political power and wealth, although these relationships are seen as gradually shifting over extended historical periods. Karl Marx (1964, 1965), who provided much of the intellectual underpinnings for conflict theory, contended that two dominant classes would arise in the industrial age: the class that owned the means of production (the bourgeoisie) and the class that provided the labor (the proletariat) (Bohm, 1982:567). He believed that so much wealth would eventually become concentrated in the hands of those controlling the means of production that the workers would revolt and establish collectives to manage the factories, thereafter sharing profits more or less equitably.
Contemporary versions of conflict theory play down the historical course of events that Marx envisioned for capitalist societies, while retaining his emphasis on class struggle for power and resources. Social classes in modern versions of conflict theory are considerably more complicated in terms of their numbers and how they are constituted and compete for power and resources (Rothman, 1993).
While numerous versions of both functional theory and conflict theory have been proposed over the years (e.g., Mills, 1956; Dahrendorf, 1959; Lenski, 1966; Hagan, Gillis, and Simpson, 1985), none of these versions has been able to account for why one gender (male) is more involved in forming and maintaining hierarchical relationships and competing for resources within these relationships than the other gender (female) (Lockwood, 1986). In particular, neither theory predicts that male domination in social hierarchies would be virtually universal throughout human societies (reviewed by Goldberg, 1993). Furthermore, neither functional nor conflict theory offers an explanation for why males in most other species are the gender which forms the most obvious social hierarchies, then struggles to attain a high dominance position within the hierarchy (reviewed by Ellis, 1995). Another inadequacy of these more traditional sociological explanations for social stratification is that they do not predict that women would have a much stronger tendency than men to prefer sex partners (especially permanent sex partners) who are of high social status (Lopreato and Crippen, 1999:232). The theory to be proposed targets these gender differences in status-striving and status-biased mating preferences as the starting point for erecting a new theory of social stratification.
THE BIOSOCIAL FEMALE CHOICE THEORY OF SOCIAL STRATIFICATION
In this article, a new theory of social stratification is offered. The theorycalled the biosocial female choice (BFC) theory-purports to explain why social hierarchies form and why males on average are more prone toward status-striving than females. Central to the present theory is the evolutionary concept of female choice, which refers to the greater tendency for females than for males to limit most mating opportunities to a relatively small number of sex partners (Ellis, 1995:301; Geary, 2000:59). The theory can be thought of in terms of five interlocking conceptual components: an evolutionary component, a genetic component, a physiological/behavioral component, a neurohormonal component, and a social learning component. Each of the five components is described separately, and then evidence bearing on various aspects of the theory is briefly discussed.
The evolutionary component of the biosocial female choice (BFC) theory has two subcomponents. One subcomponent is concerned with why social hierarchies form, and the other subcomponent focuses on why males are more prone than females to organize themselves into social hierarchies and then to overtly compete with one another for social status.
Why Hierarchies Form. The BFC theory assumes that social stratification has been naturally selected to facilitate the acquisition and utilization of resources that humans (and other animals) need to survive and reproduce. Natural selection for hierarchical distribution of resources stems in part from the fact that many resources are both rare and clumped in time and/or space. When clumping is present, not every member of a social group can access the resource at once. Consequently, it is less energy-consuming for members of a social group to organize themselves hierarchically and access resources accordingly than to jostle de novo for access each time resources present themselves. For this reason, humans, like nearly all other social animals, form stratification systems, even though these systems ensure that individuals near the top of the hierarchy will receive disproportionate shares of the resources.
Put another way, the BFC theory asserts that there are two extreme options regarding the allocation of limited resources within a population. One option is to continually scramble and contest access to resources, while the other is to form hierarchies in which those at the top control resources to disproportionate degrees. As long as those at the top of a hierarchy allow most of the remaining social group members access to enough resources that those lower in the hierarchy tolerate the inequities, a stratification system will be sustained. Also, one should bear in mind that as with all social relationships, hierarchical ones change over time. Theoretically, social hierarchies that disintegrate will be either reconstituted or replaced by new hierarchies, with the transitions punctuated by emotional tension and increased physical violence. Such patterns have been well established in studies of nonhuman social animals (Robel and Ballard, 1974; Beilharz and Zeeb, 1982; Apollonio, FestaBianchel, and Mari, 1989).
The BFC theory assumes that animals who evolve social living because of advantages in feeding, protection, and reproduction must allocate scarce clumped resources either through large energy expenditures involved in scrambling for the resources, or they must form a hierarchical system. However, the only way a hierarchy can function is for those at the top to receive more than those at the bottom.
Unfortunately, individuals near the bottom often suffer relative to those higher up in the hierarchy. According to the BFC theory, all that is needed for a stratification system to maintain itself is that a sufficient number of social group members receive more resources through the functioning in the system than they would receive without it. The exact proportion of a population that is benefitting and suffering from a hierarchy cannot be estimated because the relative power to overthrow and protect a hierarchy depends on other factors, including leadership and technology.
The BFC theory directly contradicts the functionalist assumption that social hierarchies serve the interests of society as a whole. From the BFC perspective, it is primarily the reproductive interests of individual societal members (and ultimately of the genes they transmit to future generations), not society, that reaps benefits from social hierarchies.
Theoretically, during times of resource scarcity, individuals near the bottom of the hierarchy will suffer reproductively (Boone and Kessler, 1999:266). However, during times of plenty, those near the bottom of the social hierarchy often reproduce on par with those in the middle and upper strata, and should sometimes even exceed the rate of reproduction of those at the top, especially in well-organized societies.
The BFC theory is in agreement with conflict theory regarding the competitive aspects of social stratification. However, it does not conceive of hierarchies as existing in discrete classes or in terms of uni-direction exploitation (i.e., the rich exploiting the poor). According to the BFC theory, competition and exploitation are inherent features of social living and occur within and between all factions.
Why Males and Females Differ in Status-striving. The second evolutionary subcomponent in the BFC theory has to do with gender differences in social stratification. Because humans reproduce sexually, there is strong natural selection pressure for males and females to diverge in how they contribute to reproduction. The present view is that because females devote considerable time and energy gestating each offspring and males do not (Trivers, 1971), males have the most time to specialize in forming hierarchies and then competing for resources within them. In abstract terms, the gender that allocates the greatest amount of time and energy forming and maintaining social hierarchies will be the gender that spends the least time and energy directly producing offspring.
As a result of the fact that females must gestate each offspring that is produced, females have been favored by natural selection for choosing mates who are both capable of, and inclined to, assist in rearing offspring. This biased mate selection exhibited by females has come to be known as female choice (Lenington, 1980; Kodric-Brown, 1993; Ellis, 1995). Natural selection particularly favors females who bias their choices of mates toward males who are relatively good at integrating themselves into social hierarchies and then maneuvering their way up their rungs, thereby coming to control greater than average resources. Nevertheless, under good economic conditions, even males near the bottom of a social hierarchy should often be favored by natural selection for functioning within social hierarchies because of the efficiency of these hierarchies at generating and preserving resources.
Of course, females can (and do) seek to acquire essential resources on their own. By doing so to the extent that males do, females hinder their own reproductive potential relative to females who have mates who are sharing their resources with females. Theoretically, the scarcer and more essential the resources are in a population, the more natural selection will favor females who mate with males of relatively high status instead of trying to compete for the resources on their own.
Complicating this female choice strategy is the fact that status and statusstriving come in many forms, and some forms are more effective under some environmental conditions than under other conditions. Another confounding factor is that the choosier a female is, the more competition she will encounter from other females for the same high-status males. Furthermore, males will be favored by natural selection not only for becoming effective status strivers, but also for advertising and even exaggerating their statusstriving potential. These complications lead to very complex and subtle strategies and counterstrategies within and between males and females in choosing mates.
The BFC theory assumes that a substantial proportion of people’s variations in social status are due to genetic factors. This assumption must be made in order to make the even more basic assumption that natural selection contributes to variations in social status.
It is reasonable to believe that most of the genetic influences operate through complex brain functioning patterns, such as brain functions having to do with intelligence and a host of behavioral/ personality traits. These traits in turn are likely to impact occupational interests, motivations, and abilities. As societies become increasingly complex from a technological standpoint, natural selection should increasingly favor genetic variability in occupationally relevant interests, motivations, and abilities.
Other genes affecting social status are ones operating outside the brain, altering such traits as physical size and appearance, particularly height and strength. Additional genes impinging on social status are those affecting susceptibility to physical and mental diseases.
Phrases such as “genes affecting” should not be read as implying that there are specific genes for specific statusrelated traits, or that environmental factors are not also important. Genes, in fact, code only for the production of various amino acids and proteins. Such phrases as “genes promoting” are being used here as shorthand to refer to genes that commonly increase the probability of certain behavior or physical traits being manifested under a given set of environmental conditions. Some of these genes may operate through complex brain functioning patterns, while others merely affect morphological traits affecting body size and strength or internal functioning affecting health.
The BFC theory specifically assumes that genes that promote status-striving and status attainment are located on the Y-chromosome (which only males have). This assumption is vital to the theory’s explanation for gender differences in status-striving and status attainment. The theory stipulates that additional genes affecting social status-striving and attainment are probably scattered throughout the remaining chromosomes (i.e., the Xchromosome and the 22 pairs of autosomes) so as to account for much of the within-gender variation in physiological, cognitive, and behavioral traits that affect the attainment of social status.
Theoretically, genes promoting statusstriving will accumulate on the Ychromosome to a greater degree in polygynous societies than in monogamous societies. This is because males who pass their genes on at the highest rates in polygynous societies will be those with Ychromosomes that have the greatest status-promoting tendencies (Lucotte, Gerald, Krishnamoorthy, David, Aouizerate, and Galzot, 1994:524). In long-term monogamous societies, fewer genes conducive to status-striving should be carried exclusively on the Y-chromosome, meaning that the autosomes should be making a greater proportional contribution to statusstriving than in polygynous societies.
Ultimately, the BFC theory predicts that many genes, possibly hundreds, affect social status, and will be widely dispersed throughout the human genome. Furthermore, because the theory assumes that status is an evolved extension of what is termed dominance in other animals, it is safe to assume that many of the genes affecting human social status and status-striving are playing similar roles in other animals, particularly other primates. The genes on the Y-chromosome that are affecting social status may mainly serve “regulatory functions,” meaning that rather than causing status-striving directly, they primarily just help to enhance the expression of status-striving genes located on the autosomes and X-chromosome (see Hughes, Coleman, Ahmed, Cheng, Lim, and Hawkins, 1999).
The BFC theory is consistent with the view that sociocultural factors such as sex role training contribute to gender differences in status-striving and occupational interests and choices, but it is inconsistent with the view that only sociocultural factors are involved. In fact, the theory leads to the hypothesis that humans have genes that will incline parents to discriminate in their child-rearing activities so as to accentuate status-striving in boys more than in girls. Theoretically, societies (and subgroups within a society) in which daughters are equally encouraged to focus on status-striving and attainment will exhibit lower reproduction rates than societies (or subgroups) in which sons are encouraged and daughters are discouraged from doing so.
The theory assumes that the motivation for status-striving is largely unlearned, while the social skills needed to effectively express status-striving are predominantly learned. Likewise, parental desires to have reproductively viable boys and girls are mostly unlearned, while the social skills required to produce such children are largely learned.
In addition to postulating the evolution of genes for status-striving and attainment, the BFC theory contends that genes have evolved which incline people to flaunt and exaggerate their status attainment and potential. These “puffery” genes should be most strongly expressed among males, especially when they are actively involved in courtship, since males will reproductively benefit more than females will from displaying/ exaggerating their status. If this line of reasoning is correct, it would complement Thorstein Veblen’s (1899) assertion that the upper social classes often engage in what he termed conspicuous consumption. Theoretically, males should be more conspicuous consumers than females.
If females have evolved tendencies to prefer males who can accumulate and maintain control over resources, males should have evolved physiological as well as behavioral traits that help them to “comply” with these female preferences. Theoretically, physical traits such as body size, strength, and a deep voice are among the physiological adaptations males have made to female preferences for high resource acquisition and retention abilities. In other words, the evolutionary reason males are taller, stronger, and have deeper voices than females (especially following puberty) is that these are among the traits that males use to compete for social status. These traits should also be among those that females are attracted to when choosing mates, especially females with the greatest reproductive success.
Behavioral and personality traits such as intelligence, ambition, generosity, hard work, and the ability to work as part of a functionally interdependent team should also be attractive to females. In other words, the BFC theory predicts that females will be more sexually attracted to these status-promoting traits than males will be. Finding societies whose members are flourishing reproductively where males prefer and/or choose mates based on status-striving and attainment traits more than females do would be extremely detrimental to the BFC theory.
The BFC theory asserts that evolution has produced substantial average differences in brain functioning of men and women, and that these differences contribute a great deal to the average gender differences in social status-striving. This line of reasoning implies that male brains must function in ways that promote status-striving and resource procurement, while female brains should function in ways that incline them to be attracted to these male behavior patterns.
As to how the brains of males promote resource procurement activities, the BFC theory postulates that developmental hormonal regimens play an important role. In particular, exposing the brain to testosterone (and related sex hormones) appears to be crucial (Lopreato and Crippen, 1999:235).
Testosterone production is under the influence of several genes on the Ychromosome working in conjunction with genes on the autosomes and Xchromosome, and these influences unfold in two stages. The first stage, called the perinatal or organizational stage, occurs primarily during fetal development. In this stage, the male body, including the brain, receives relatively high testosterone exposure (Ellis and Ames, 1987). According to the BFC theory, perinatal exposure of the brain to testosterone inclines males to exhibit what may be called environment-manipulating and environment-exploring behavior to a greater degree than occurs in females.
These behavioral tendencies set the stage for a variety of interests and abilities that males will later use to rise in social status by filling a wide spectrum of occupational niches. Consequently, the BFC theory predicts that in all cultures males will exhibit greater occupational diversity than females. (Theoretically, most femaledominated occupations should be mere extensions of different aspects of childcare-giving activities.)
The second stage of gender differentiation is the postpubertal or activational stage, which occurs following the onset of puberty. During this stage, the average male brain is exposed to testosterone levels that are several times higher than is the case for the average female brain (Khan and Cataio, 1984:10; Malasanos, Barkauskas, Moss, and StoltenbergAllen, 1986). Theoretically, this second stage serves to fully engage the behavioral tendencies that were laid down in the first stage.
According to the BFC theory, male and female brains are sexed in such ways as to decrease male pain sensitivity, both in terms of personal sensations and in terms of relating to the pain experienced by others. Evidence supporting this proposal comes from studies showing that males tolerate pain of greater intensities than females, both in humans and in other mammals (reviewed by Berkley, 1997; Riley, Robinson, Wise, Myers, and Fillingim, 1998). Other supportive evidence comes from studies suggesting that males are less empathetic than females (Simmer, 1971; Hoffman, 1977; Zahn-Waxler, Radke-Yarrow, Wagner, and Chapman, 1992; Zahn-Waxler, Robinson, and Erode, 1992).
Theoretically, gender differences in pain sensitivity and empathy have the effect of making males more aggressive and more likely to focus on the end result of their actions than on the process whereby these ends are achieved. Such a focus combined with male tendencies to explore and manipulate the physical environment facilitates their tendencies to learn numerous technical and organizational occupations. This line of reasoning is at odds with those who have contended that males and females have equal biological potentials regarding the learning of nearly all occupations (e.g., O’Kelly and Carney, 1986; Nielsen, 1990).
Even though the BFC theory asserts that testosterone plays a key role in making men inclined to fill a wider diversity of occupations than women, this does not mean that any simple relationship exists between social status and either perinatal or postpubertal testosterone levels. Instead, testosterone levels during these two stages of development appear to have complex interactive effects on brain functioning patterns that ultimately impact occupational preferences and abilities.
SOCIAL ENVIRONMENTAL COMPONENT
The social environmental component of the BFC theory of social stratification primarily has to do with the influence of parents on occupational preferences and abilities. As noted earlier, over countless generations, parents should have been under natural selection pressure to be keenly interested in the gender of their offspring, and in tailoring their rearing practices accordingly. In particular, parents who seek to minimize, rather than foster, gender differences in behaviorparticularly in the area of status-striving -will be disfavored by natural selection. More precisely, parents who succeed in encouraging their sons to develop statusstriving interests and abilities should have more grandchildren than parents who succeed in discouraging such male tendencies. Likewise, according to the BFC theory, parents who encourage their daughters to maximally express statusstriving interests and abilities will have fewer grandchildren than parents who encourage their daughters to develop childcare interests and to adopt physical appearances and behavioral skills attractive to members of the opposite sex.
A GRAPHIC SUMMARY OF THE BFC THEORY
Figure 1 presents a summary of the main elements of the BFC theory. Starting from the far left, genes for brain functioning patterns which promote preferences and behavioral tendencies conducive to forming hierarchical social relationships and status-striving are shown leading to status attainment. Statusstriving and attainment, in turn, take place within an arena of mate selection, the key element of which is female preference for status-striving mates.
According to the BFC theory, even gender-neutral rearing efforts will result in male-female inequality in statusstriving and attainment because the genetic and neurohormonal factors have evolved to ensure sex differences in status-striving and preferences for mates according to such striving. These theoretical deductions are certainly not what feminists and other supporters of gender equality have contended, but they are testable hypotheses that make the BFC theory highly vulnerable to disproof.
EVIDENCE PERTAINING TO THE BFC THEORY
Based on the propositions presented thus far, the BFC theory of social stratification may be summarily stated as follows: Social stratification is central to an evolved social system regulating the distribution of resources. These resources are among the factors affecting the rate at which members of a society reproduce.
At the heart of the BFC theory is the proposition that control over resources differs according to gender. In particular, it maintains that males will become more directly involved than females in forming social hierarchies and in striving to rise within these hierarchies. This gender difference has evolved because females have been favored by natural selection for choosing high-status males as sex partners, while males choose mates primarily using non-status criteria, such as evidence of fecundity and maternal investment capabilities.
GENDER DIFFERENCES IN PREFERENCES FOR MATES
In keeping with the evolutionary component of the BFC theory, one can predict that when choosing mates, females will place a higher premium than males will on partner social status. Not only are high-status males more likely than lowstatus males to have the means for providing sustained support for offspring, they would also be more likely to pass genes for similar capacities on to their descendants. Consequently, a female who focuses on status, or status potential, in choosing mating partners will be favored by natural selection; this should be a culturally universal tendency.
Evidence is largely consistent with such a prediction. The most broad-ranging test was provided by a study of 37 cultures in which both men and women were asked to identify the traits they found most attractive in terms of marriage partners. In all of these cultures, status-related traits were identified by females as being more important than the traits identified by males as those they looked for in choosing mates (Buss et al., 1989). Earlier studies also found that females were more likely than males to express preferences for mates of high social status (Goldschmidt, 1976:208; Langhorne and Secord, 1955; Hudson and Henze, 1969; Kemper and Bologh, 1980; Davis, 1990). Parenthetically, studies of other animals also suggest that females in most species use dominance-related criteria more than males do in choosing sex partners (reviewed by Ellis, 1995).
SOCIAL STATUS AND REPRODUCTIVE SUCCESS
According to the BFC theory, women who marry high-status men will achieve greater reproductive success than women who marry low-status men. Conversely, men who marry high-status women should diminish their reproductive success provided that the women were instrumental in attaining their own status.
The main reason for this gender inconsistency in the relationship between social status and reproductive success is that women who marry high-status rather than low-status males can divert more of their time and energy to bearing children without depleting the resources needed for rearing children. On the other hand, men who marry women who have independently attained high social status will nearly always have spouses who have diverted significant proportions of their reproductive time and energy toward nonreproductive ends. As summarized below, considerable research based on a variety of SES and reproductive success measures supports the theory’s predictions for both males and females.
In the case of females, studies in several parts of the world have shown that women who attain high status-measured in terms of years of education-have fewer children than do women with less education (Kasarda, Billy, and West, 1986; Weinberger, Lloyd, and Blanc, 1989; Bachu, 1991; Grindstaff, Balakrishan, and Dewit, 1991). Studies conducted in the United States have shown that, independent of the incomes of any spouses they may have, women with high personal incomes have fewer children than women with low personal incomes (Freedman, 1962; Whelpton et al., 1966; Mott, 1972; Groat et al., 1976; Felmlee, 1993).
Regarding males, most evidence suggests that high status (measured in terms of wealth) is associated with increased reproductive success, except in the case of twentieth-century industrialized societies. The supportive studies come from fifteenth-century Italy (Morrison, Kirshner, and Molha, 1977), eighteenthcentury Germany (Klindworth and Voland, 1995) herding African society (Borgerhoff Muller, 1990), the Middle East (Irons, 1979), and a horticultural South American tribe (Chagnon, 1988). A study in contemporary Hungary also found a positive correlation between men’s years of education and the number of children they produce (Bereczkei and Csanaky, 1996).
The studies that have found an inverse relationship between social status and male fertility have been conduced in the following twentieth-century industrialized societies: the United States (Lancaster, Boch, and Johnson, 1995), France (Haines, 1992), Canada (Charles, 1949), and Australia (along, 1980). This reversal is explained by the BFC theory as resulting from the abundance of subsistence resources made available in advanced industrialized societies. Such abundance ensures that at least subsistence levels of resources will be available to virtually all societal members. Theoretically, if this broad-ranging availability of subsistence resources ever evaporates, the reproduction rates of those at the bottom of the social hierarchy will once again be surpassed by those in the upper strata, especially in the case of males.
The inverse relationship between social status and male reproductive success found in several advanced industrialized societies seems to have parallels in animal research on dominance and male reproductive success. While some exceptions have been documented, especially in the primate order, high-status males in most animal species out-reproduce lowdominance males (reviewed by Ellis, 1995; Bercovitch and Nuernberg, 1996). The BFC theory predicts that the exceptions will occur in animal populations that are being artificially provisioned by human researchers, since artificial feeding can be considered analogous to human conditions in which at least subsistence resources are available to virtually all societal members.
GENDER DIFFERENCES IN STATUSRELATED ACHIEVEMENTS
Many social scientists are inclined to attribute the fact that men surpass women in many areas of occupational achievement to discrimination and sex role training. The BFC theory envisions these factors as having minor effects on achievement differences.
Theoretically, because women prefer high-status mates, men should achieve more in virtually all occupational realms associated with social status. This would not only account for why men are more prevalent than women as politicians and corporate executives, but also why they are responsible for twenty times as many jazz albums, eight times as many works of art, and three times as many books as women (Miller, 1999). The long history of men’s domination in scientific achievements also meshes with the BFC theory of social stratification, including the evidence that most of their greatest achievements occur relatively early in their careers, when the effort can still impact reproduction (Kanazawa, 2000).
GENDER DiFFERENTIALS IN EARNINGS
The BFC theory predicts an average disparity in earnings between men and women in favor of men. This disparity should be evident in all societies with monetary economies, although the degree of disparity will vary depending on governmental and other cultural practices. According to the theory, this disparity results from females biasing mate choices on the basis of earnings (and earnings potential) to a much greater degree than is true for mating choices by males. Consistent with the BFC theory, studies throughout the world have indicated that the average male earns more than the average female (e.g., Bane, 1976; England, 1979; Rosenfeld, 1980).
Not only do women earn less than men for comparable hours of work, but they are also less likely to rise into managerial positions (Baron, Davis-Blake, and Bielby, 1986:270). The BFC theory explains this not in terms of male discrimination against females in the work place, but in terms of female discrimination in mate selection. In other words, the more females have historically biased their choices of sex partners toward males of high social status (or status potential), the more difficulty females in contemporary times will have competing against males in attaining high occupational status.
Regarding labor participation by females, the theory asserts that the more females participate, the more they sacrifice in the way of lifetime fertility (SmithLovin and Tickamyer, 1978). Males do not make a comparable reproductive sacrifice by devoting time and energy to developing most occupational skills. Consequently, except under very unusual conditions, females who are as committed as males are to status-striving will leave relatively few of their genes in subsequent generations. Since the BFC theory assumes that these status-striving tendencies are genetically influenced, one cannot escape predicting that there will always be a significant degree of gender difference in status-striving, and thereby in status achievement.
FERTILITY AND TYPES OF OCCUPATIONAL INTERESTS
According to the BFC theory, females in all societies will focus more time and energy on caring for infants than is true for males. This focus should reveal itself in many ways, including distinctive gender roles and biases in occupational interests. For example, one would expect an unusually high proportion of women to choose occupations dealing with helping people (especially children), whereas males should focus their occupational interests more broadly, including occupations having to do primarily with taskoriented manipulations of objects and people. One would expect that the occupations chosen by men should also have more competitive elements than occupations chosen by women. The evidence is generally supportive of at least the first of these hypotheses, in that males seem to gravitate toward occupations that primarily manipulate physical objects, while females are clustered in occupations dealing with care for people, particularly children (Hall, 1969:334; Harkness and Super, 1992).
A corollary of this hypothesis is that females who exhibit the greatest interests in occupations that involve child care will reproduce at higher rates than women whose interests have little to do with child care. In other words, the more women gravitate toward male-dominated occupations, the lower their reproduction rates should be. The BFC theory assumes that genetic factors (mediated by neurohormonal factors) contribute to both betweenand within-gender differences in occupational interests.
GENETIC INFLUENCES ON SOCIAL STATUS
The theory hypothesizes that most, if not all, traits contributing to variations in social status should be genetically influenced (but not genetically determined). Evidence bearing on this hypothesis comes primarily from twin and adoption studies that have sought to estimate genetic influences on education, occupational prestige, and earnings in industrial societies.
Regarding educational achievement, both twin and adoption studies have found that genetic factors make significant contributions to the number of years of education completed (Willerman, Horn, and Loehlin, 1977; Fulker, 1978; Teasdale and Owen, 1984; Heath, Berg, Eaves, Solaas, Corey, Sundet, Magnus, and Nancy, 1985; Tambs, Sundet, Magnus, and Berg, 1989; Thompson, Detterman, and Plomin, 1991). Evidence of genetic influence has also been found for educational achievement as assessed in terms of grade point averages (Vandenberg, 1969; Scarr and Weinberg, 1983). While these findings suggest that genes are important, none of these studies refutes the importance of environmental factors. Typically, about half of the variation in educational achievement explained by these studies has been attributed to genetic influences.
In the case of occupational prestige, the evidence of genetic influence comes primarily from studies of twins. These studies found identical twins attaining more comparable levels of occupational prestige than those of fraternal twins (Carter, 1932; Vandenberg and Kelly, 1964; Vandenberg and Stafford, 1967; Loehlin and Nichols, 1976; Fulker, 1978; Tambs and Sundet, 1985). One adoption study also found evidence of a modest genetic influence (Grotevant, Scarr, and Weinberg, 1978:90). Furthermore, one study of fraternal twins reared apart since birth (a combined twin/adoption study) found that they exhibited significantly greater similarity in their career interests and occupational choices than did genetically unrelated persons reared apart (Moloney, Bouchard, and Segal, 1991).
With regard to earnings, the evidence pertaining to a possible genetic influence is limited to a single twin study of males. The results support the hypothesis that significant variation in earnings can be attributed to genetic factors (Behrman, Hrubec, Taubman, and Wales, 1980:30).
How might genes affect an individual’s ability to achieve high social status? There are at least four possibilities that are all feasible within the confines of the BFC theory. First, genes could influence intelligence, thereby impacting educational attainment. Educational attainment, in turn, could affect occupational prestige and income. Consistent with this reasoning are a number of twin and adoption studies indicating that about half of the variation in intelligence is attributable to genetic factors, although none of the specific genes have yet been identified (Bouchard and McGue, 1981; Teasdale and Owen, 1984; Tambs, Sundet, and Magnus, 1986; Thompson, Detterman, and Plomin, 1988; Bouchard, Lykken, McGue, Segal, and Tellegen, 1990; Plomin and Neiderhiser, 1992; Thompson, Detterman, and Plomin, 1993).
A second possibility is that genes alter brain functioning in ways that affect interests, thereby influencing occupational choices. Occupational choices, in turn, could affect income, quite apart from the influence of mere years of education obtained. As noted above, the evidence bearing on this possibility is fairly supportive.
Third, genes could influence social status by altering basic ambition and “status-striving.” In order to make statusstriving more pronounced in males, some of the genes would almost certainly need to be located on the Y-chromosome. No evidence directly supporting or refuting this line of reasoning was located.
The fourth possibility is that genes affect all aspects of social status attainment by influencing resistence to various physical and mental illnesses. Along these lines, twin studies indicate that genes affect susceptibility to a variety of diseases (Feinleib, Garrison, and Fabsitz, 1977; Harsanyi and Hutton, 1981; Gedda, Rajani, Brenci, Lun, Talone, and Oddi, 1984) and play a role in determining overall life expectancy (Jarvik, Falek, Kallman, and Lorge, 1960; Carmelli and Andersen, 1981). Regarding mental illnesses, twin studies have implicated genetic factors in depression (Kendler, Kessler, and Walters, 1995; van den Oord and Rowe, 1997:328; O’Connor, Neiderhiser, Reiss, Hetherington, and Plomin, 1998a; O’Connor, Reiss, McGuire, and Hetherington, 1998b), in schizophrenia (Kendler and Bovinette, 1983; Onstad, Skre, Torgensen, and Kringlen, 1991; Stabenau and Pollin, 1993; Gottesman, 1994), in alcoholism (Pederson, Friberg, Floderus-Myrhed, McClean, and Plomin, 1984; Kaprio, Koskenvuo, Langinvainio, Romanov, Sarna, and Rose, 1987; Johnson, Van der Bree, and Pickens, 1996; Prescott and Kendler, 1996) and in drug use/abuse (Kaprio, Koskenvuo, and Sarna, 1981; Heath and Martin, 1993; Tsuang, Lyons, Eisen, Goldberg, True, Lin, Meyer, Toomey, Faraone, and Eaves, 1996). If this line of reasoning has merit, one would hypothesize that persons of high social status would be unusually resistant to physical and mental illnesses that impede the attainment and/or maintenance of social status.
SOCIAL STATUS AND PHYSICAL SIZE, STRENGTH, APPEARANCE, AND TENOR OF VOICE
According to the BFC theory, a positive relationship should exist between social status and such traits as physical size, strength, deep voice tone, and general masculine/rugged appearance. This is partly because these traits should serve as cues of status attainment potential, which females use to discriminate relatively desirable mates. Theoretically, throughout the history of social animals, females who prefer relatively large, strong, and rugged males with low (authoritative/intimidating) voices will have been more successful in mating with high-status males than females who lack such preferences.
Most of the evidence pertaining to the above predictions is confined to the study of height. A review of 160 studiesconducted throughout the world, with some extending back more than a century -revealed that 97 percent of the available studies found significant positive relationships between social status (variously measured) and height, particularly among males (Ellis, 1994:108). Regarding voice, as the theory predicts, a Dutch study found that women do find deep male voices more attractive than relatively high male voices (Collins, 2000). Furthermore, the BFC theory leads one to expect that male voices will be used more often than female voices whenever persuasion depends more on the authority of a messenger than on the strength of the evidence. Such reasoning could help to explain why males seem to predominate in political and religious leadership throughout the world. In this connection, studies of television commercials have found that advertisers used male voiceovers more often than female voice-overs (Doolittle and Pepper, 1975; Culley and Bennett, 1976).
In the case of facial features, a recent study found women generally preferring rugged masculine features over faces that were less masculine in appearance (Johnston, Hagel, Franklin, Fink, and Grammar, 2001). In the present context, one can hypothesize that this preference mainly evolved over countless generations because males with relatively rugged facial features attain aboveaverage social status and as a consequence attract more mating partners.
MALE SEX HORMONES AND STATUS-PROMOTING TRAITS
Genes on the Y-chromosome play a key role in sexual differentiation by causing would-be ovaries very early in gestation to become testes instead (Grambach, 1979:34; von Berswordt-Wallrabe, 1983:110). Once the testes have formed, they become specialized glands for producing testosterone, which enhances a variety of masculine physical and behavioral traits (Roberts, 1988; Gorski, 1987; Kimura, 1992; Swaab, Gooren, and Hofman, 1992). According to the BFC theory, many of the masculine traits having to do with status-striving and status attainment are enhanced by exposing the brain and other bodily organs to relatively high (male-typical) levels of testosterone. Among these traits are physical strength, motivation, and intelligence, each of which is considered individually below.
Strength. In the case of strength, testosterone facilitates muscularization, particularly of the upper body (Martin, 1985). This increased muscularization makes individuals better able to use force and intimidation to acquire and retain control over resources. In addition, musculature contributes to competence in a variety of manual occupations. It is hypothesized that muscularization is more pronounced in males than in females because strength promotes male reproduction more than it promotes female reproduction. This reproductive advantage comes partly from using force and intimidation against rivals for scarce resource procurement. In technologically complex societies, males who gravitate toward most manual occupations also gain reproductively by performing in these occupations with minimal physical injury and exhaustion. No direct evidence was found to support or refute this line of reasoning.
Motivation. The BFC theory leads to the hypothesis that males will be more motivated toward status-promoting tasks than females, and implies that this greater motivation is achieved in part by the influence of testosterone on brain functioning. This hypothesis is consistent with studies from several countries indicating that men feel more committed to work (outside the home) than do women (Leviatan, 1976; Palgi, 1976; Saleh and Lalljee, 1969). Interestingly, this greater commitment does not appear to be attributable to men having any greater job satisfaction than women (Mednick, 1975).
Supporting BFC theory are United States studies indicating that males exhibit higher levels of competitiveness (Spence and Helmreich, 1978; Ahlgren and Johnson, 1979; Olds and Shaver, 1980) and various forms of achievement motivation than do females (French and Lesser, 1964; Veroff, 1969). If the BFC theory is correct, these tendencies should be universal.
Regarding the possible role of neuroandrogenic factors, studies of various species have found animals who are perinatally exposed to high levels of testosterone exhibit greater tenaciousness at various tasks than animals exposed to low testosterone levels (Andrew and Rogers, 1972; Ellis, 1986:533). While experimental studies of humans have not been performed, men appear to persist at tasks in the face of failure and disparaging comments significantly longer than do women (Battle, 1965; Deaux, White, and Farris, 1975; Dweck and Gilliard, 1975; Nicholls, 1975). These lines of evidence would be consistent with the hypothesis that, relative to females, males have evolved brain functioning patterns that are more conducive to the sort of tenaciousness that promotes status-striving.
Another aspect of brain functioning that is likely to have evolved in males to a greater degree than in females in order to facilitate male resource provisioning is spatial reasoning. Superior spatial reasoning would assist males living in foraging societies to hunt efficiently. In societies with many specialized occupations, spatial reasoning would be advantageous in nearly all occupations other than those involving the care and nurturing of others. Evidence that males surpass females in spatial reasoning, both in humans (Hakstian and Cattell, 1975; Stumpf and Eliot, 1995; Hattori, 1999) and in other species (Kraemer and Randall, 1995; Cimadevilla et al., 1999), is consistent with this line of reasoning, although the specific aspects of brain functioning that promote such sex differences remain to be identified. The BFC theory predicts that altered brain functioning promoting such cognitive and behavioral sex differences will involve the influence of testosterone and will be linked in part to genes on the Y-chromosome.
BOASTING AND CONSPICUOUS CONSUMPTION
The BFC theory leads one to expect that males will be more likely than females to openly display and even exaggerate their status and status-achieving potential. Theoretically, male efforts in this regard will be especially prominent during the times in their lives when they are most actively involved in seeking to attract mates. Two studies were found specifically bearing on this hypothesis, both of which found males to be more prone to brag about status-related accomplishments than were females (Sheehy, 1938; Vollmer, 1984). In addition, a study of grade-school children found that boys engaged in “self-promoting” behavior more than girls during same-sex play (McCloskey and Coleman, 1992). According to the BFC theory, males are genetically programmed to behave this way as part of their evolved reproductive strategy. Skeptics may dismiss the findings from these studies as simply reflecting cultural training unique to the United States (where all three studies were conducted). To help settle the issue, research should be conducted in remote parts of the world. If the BFC theory is correct, such gender differences will be universal (with the possible exception of societies bordering on extinction).
SUMMARY AND DISCUSSION
Sociological efforts to “build a comprehensive theory of stratification” have been ongoing for decades (Colins, 1971:1002). This paper presents a continuation of this effort. The theory that has been formulated addresses a broader spectrum of stratification phenomena than either of its two rivals-i.e., functional theory and conflict theory. Both of these more traditional theories apply only to humans and are essentially silent with respect to accounting for gender differences in social status-striving and achievement. These are serious flaws in light of the pervasiveness of social hierarchies outside the human species and the fact that in all societies dominance is a more pronounced aspect of male than of female behavior.
At the heart of the present theory is the idea that gender differences in control over resources can only be scientifically explained in terms of the fact that females can best reproduce when they have a stable supply of resources with which to bear and rear offspring. The theory is called the biosocial female choice (BFC) theory because it assumes that males and females have been favored by natural selection for adopting differing approaches to reproduction, ones in which males have become specialists in forming social hierarchies and competing for resources within these hierarchies.
Theoretically, most females emphasize seeking mates who are stable resource providers, rather than obtaining needed resources on their own, thereby diverting time and energy away from offspring care. Given this female emphasis, males have been sexually selected for focusing time and energy on status-striving. Males who have done so have tended to leave more offspring in past generations than males who have not done so. As a result of males being selected for status-striving and status attainment, males have acquired both physical and behavioral traits that tend to facilitate status attainment.
The theory also asserts that human tendencies to form hierarchies evolved out of the reproductive advantages resulting from accumulating resources inequitably. Theoretically, inequitable resource accumulations allow those near the top of the hierarchy to devote time to developing increasingly efficient ways of exploiting the world’s resources and distributing them to those who assist in refining and maintaining the exploitation methods. Another evolutionary reason for social stratification is that it facilitates the reproduction of nearly everyone living in stratified societies relative to those living in relatively non-stratified societies except when resources become scarce.
Unlike functional theory, the BFC theory does not assume that hierarchies exist for the betterment of society as a whole. Rather, the benefits derived from social stratification are in terms of reproduction rates of most individuals comprising a society. Theoretically, the reproductive benefits will vary depending on the availability of resources. During times of plenty, all levels in a hierarchy should reproductively benefit from living within a wellorganized social hierarchy. During extended economic downturns, however, increasing proportions of the reproductive benefit of a social hierarchy will be enjoyed by those near the top. However, those near the top have a reproductive interest in increasing resource availability to other societal members in order to avoid serious challenges to their privileged positions.
The present theory is compatible with the assumption that most conflict theorists make that social classes compete with one another for resources. However, there are three important differences: First, nothing in conflict theory envisions resource competition in terms of differential reproduction rates, an assumption that is at the heart of the BFC theory. Second, whereas conflict theory conceptualizes conflict as based on identifiable social classes, the BFC theory is more compatible with the idea of social stratification existing more as a continuum than as discrete classes, and recognizes that many people oscillate along this continuum to a substantial degree throughout their lives. Third, conflict theorists often point to instances of the wealthy segments of society exploiting the poor. From the perspective of the BFC theory, the concept of exploitation is not really an empirically relevant concept, except in terms of shifts in reproduction rates. In this regard, the upper social strata would only be exploiting the lower strata during economic downturns, when their reproduction rates are hypothesized to rise in relative terms. However, such a line of reasoning would imply that the lower social strata tend to exploit the upper strata during times of plenty should their reproduction rates rise in relative terms.
To account for why males occupy most of the top positions in all human social hierarchies (Goldberg, 1993), the theory stipulates that a complex set of neurohormonal forces have been naturally selected. Theoretically, these neurohormonal factors help to make it possible for males to learn effective ways of functioning within a social hierarchy. Some of the genes for male tendencies to function in social hierarchies are hypothesized to be located on the Y-chromosome, while many (and probably most) are assumed to be scattered throughout the remaining chromosomes.
The BFC theory is offered in the spirit of free scientific inquiry. Critics are invited to identify specific deficiencies in the theory’s ability to explain what is empirically discovered about social stratification, both now and in the future.
*I am grateful to Steven Goldberg, Myna Nelson, and Anthony Walsh for their helpful comments.
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