ORIGINS OF SEX DIFFERENCES IN HUMAN BEHAVIOR

The Origins of Sex Differences in Human Behavior:

Evolved Dispositions Versus Social Roles

Alice H. Eagly and Wendy Wood

Northwestern University Texas A&M University

Manuscript submitted for publication; not for citation

Comments appreciated: send to eagly@nwu.edu and wlw@psych.tamu.edu

Abstract

The ultimate causes of sex differences in human behavior can lie mainly in

evolved dispositions that differ by sex or mainly in the differing

placement of women and men in the social structure. The present article

contrasts these evolutionary and social structural origin theories of sex

differences and illustrates the explanatory power of each theory to account

for sex differences in mate selection preferences, a research area that

often has been interpreted as providing support for evolutionary

perspectives. A reanalysis of Buss's (1989a) 37 cultures study of sex

differences in attributes valued in potential mates provided strong support

for the social structural account of cross-cultural variation in sex

differences in mate preferences.

The Origins of Sex Differences in Human Behavior:

Evolved Dispositions Versus Division of Labor

As more research psychologists have become willing to acknowledge that some

aspects of social behavior, personality, and abilities differ between women

and men (e.g., Eagly, 1995; Halpern, 1997), their attention has begun to

focus on the causes of these differences. Debates about causes center at

least in part on determining what can be considered the basic or ultimate

cause of sex differences. Theories of sex differences that deal with causes

at this level are termed in this article origin theories (Archer, 1996). In

such theories, causation flows from a basic cause to sex-differentiated

behavior, and biological, psychological, and social processes mediate the

relation between the basic cause and behavior. In this article, we consider

two types of origin theories: One of these implicates evolved psychological

dispositions, and the other implicates social structure. Evolutionary

psychology, as illustrated in the work of Buss (1995a), Kenrick and Keefe

(1992), and Tooby and Cosmides (1992), thus represents the first type of

origin theory, and social psychological theories that emphasize social

structure represent the second of type of origin theory (e.g., Berger,

Wagner, & Zelditch, 1985; Eagly, 1987; Eagly & Wood, 1991; House, 1981;

Lorenzi-Cioldi, in press; Ridgeway, 1991; Ridgeway & Walker, 1995; West &

Zimmerman, 1987; Wiley, 1995).

In the evolutionary origin theory, the critical causal arrow points from

evolutionary adaptations to psychological sex differences. Because women

and men possess sex-specific evolved mechanisms, they differ

psychologically and tend to occupy different social roles. In contrast, in

the social structural origin theory, this critical causal arrow points from

social structure to psychological sex differences. Because of the division

of labor, women and men become psychologically different in ways that

adjust them to their respective social roles.

One important feature is shared by these two origin theories: Both offer a

functional analysis of behavior that emphasizes adjustment to environmental

conditions. However, the two schools of thought differ radically in their

analysis of the nature and timing of the adjustments that are most

important to sex-differentiated behavior. Evolutionary psychologists

believe that females and males faced different pressures in primeval

environments when the human species evolved and that the sexes' differing

status with respect to reproduction was the key feature of ancestral life

that framed sex-typed adaptive problems. The resolutions of these problems

produced sex-specific evolved mechanisms that humans carry with them as a

species and that are held to be the root cause of sex-differentiated

behavior. Although many evolutionary psychologists readily acknowledge the

abstract principle that environmental conditions can influence the

development and expression of evolved dispositions in individual lives,

variation of sex differences in response to individual, situational, or

cultural conditions is rarely investigated systematically (e.g., Archer,

1996; Buss, 1995b; Buss & Kenrick, 1998). For example, Buss (1998, p. 421)

emphasized "universal or near-universal sex differences" in preferences for

long-term mates, although he acknowledged some bases for cultural variation

in certain aspects of mating strategies.

Social structuralists maintain that the particular situations faced by

women and men are quite variable across societies and historical periods as

social organization changes in response to technological, ecological, and

other transformations. From a social structural perspective, a society's

division of labor between the sexes is the engine of sex-differentiated

behavior, because it summarizes the social constraints under which men and

women carry out their lives. Sex differences are viewed as accommodations

to the differing restrictions and opportunities that a society maintains

for its men and women, and sex-differentiated behavior is held to be highly

contingent on a range of individual, situational, and cultural conditions

(see Deaux & LaFrance, 1998). Despite this emphasis on the social

environment, social structuralists typically acknowledge the importance of

some biological sex differences. As Eagly (1987) argued, physical

differences between the sexes, such as men's greater size and strength and

women's childbearing and lactation, are very important because they

interact with shared cultural beliefs, social organization, and the demands

of the economy to influence the role assignments that constitute the sexual

division of labor within a society (Wood & Eagly, 1998).

These thumbnail sketches of these two origin theories should make clear

that this debate about the ultimate cause of sex differences cannot be

reduced to a simple nature versus nurture dichotomy. Both evolutionary

theory and social structural theory are interactionist in the sense that

they take biological and environmental factors into account, but they treat

these factors quite differently. Evolutionary theory views sex-specific

evolved dispositions as psychological tendencies that were built in through

genetically mediated adaptation to primeval conditions; the theory treats

contemporary environmental factors as cues that interact with adaptations

to yield sex-typed responses. Social structural theory views

sex-differentiated tendencies as built in through learning-mediated

accommodation to the contemporaneous sexual division of labor; in this

approach, physical differences between the sexes can serve as important

constraints on role assignment.

Another caution is that these theories do not merely reflect different

levels of analysis. Some attempts to reconcile the two perspectives have

proposed that social structural theories identify proximal, contemporaneous

causes for the behavior of women and men, whereas evolutionary analyses

invoke more distal causes that arose early in human history (e.g.,

Borkenau, 1992; Jackson, 1992; Schaller, 1997). Although the timing of the

human adjustment to environmental conditions that is deemed critical is

indeed different in the two theories, they propose causes that are similar

in their position on the proximal versus distal continuum of causality.

Both theories thus propose psychological causes (i.e., evolved

dispositions, role expectations) that operate in the present and whose

impact on behavior is in turn mediated by a range of more proximal

psychological processes (e.g., attitudes and beliefs). The social

structural perspective is thus in stark contrast to evolutionary psychology

models that attribute sex differences in contemporary society to sex-typed

evolved mechanisms (e.g., Buss, 1995a; Tooby & Cosmides, 1992). The causes

of sex differences in evolutionary psychology involve these mechanisms,

which are intended to replace the social psychological mechanisms featured

in theories that give a key role to social structure.

It also would be inappropriate to conclude that social structural theory is

incompatible in general with an evolutionary approach. The evolutionary

perspective is broad and encompasses many specific theories in addition to

the models featured in contemporary evolutionary psychology in the writings

of Buss (Buss, 1995a, 1996; Buss & Kenrick, 1998) and other scholars (e.g.,

Daly & Wilson, 1998; Tooby & Cosmides, 1992). Social structural analyses

suggest an evolved organism, but one in which evolutionary pressures

yielded broad dispositions such as the capacity for group living or for

culture. These analyses do not imply that people's minds are blank slates,

because humans possess facilities, such as for language, that develop in

certain ways, given appropriate environments.

To illustrate the contrasting approaches of these two theories, we will

first present and discuss each theory. Then we will examine their

predictions concerning the criteria men and women use in selecting mates.

This domain of behavior has been central to evolutionary theorizing about

human sex differences (e.g., Buss & Schmitt, 1993; Kenrick & Keefe, 1992),

and the cross-cultural findings available in this area provide an excellent

opportunity to examine empirically some of the divergent predictions of

evolutionary and social structural analyses.

Evolutionary Psychology as an Origin Theory of Sex Differences

From an evolutionary perspective, human sex differences reflect adaptations

to the pressures of the differing physical and social environments that

impinged on women and men during primeval times when the human species

emerged in its anatomically modern form (Buss, 1995a; Tooby & Cosmides,

1992). Evolutionary psychologists thus label those environments that

produced a species' evolved tendencies as its environment of evolutionary

adaptedness, abbreviated as the EEA (Cosmides, Tooby, & Barkow, 1992;

Symons, 1979, 1992; Tooby & Cosmides, 1990b). They loosely identify the

Pleistocene era as the human EEA and generally assume that these

environments were populated by hunter-gatherer groups. To the extent that

ancestral women and men faced different adaptive problems in the EEA, the

two sexes developed different strategies to ensure their survival and

maximize their reproductive success. The resolutions to sex-linked survival

and reproductive problems produced evolved psychological mechanisms that

are specific to each problem domain and that differ between women and men.

Humans then carry these sex-differentiated mechanisms with them as a

species, along with the mechanisms shared by the two sexes.

Although the evolved mechanisms that characterize humans developed in

response to the types of problems consistently encountered by humans'

ancestors and thus are universal attributes of humans, environmental input

affects how these mechanisms develop in individuals and how they are

expressed in behavior (e.g., Buss & Kenrick, 1998). Because culture

influences developmental experiences and patterns current situational

input, culture is in principle important to the expression of adaptive

mechanisms (Tooby & Cosmides, 1992). However, evolutionary psychologists

have devoted relatively little attention to the interaction between such

environmental contexts and the evolved mechanisms that underlie sex

differences. The contextual factors they have considered generally relate

very narrowly to their hypothesized mechanisms-for example, Buss (1991)

maintained that, in order for women to exercise their evolved preference

for men who offer resources, men who vary in resources must be present.

Because of this relative neglect of context, evolutionary psychologists

have generated little understanding of how variation in sex-differentiated

behavior arises from developmental factors and features of social structure

and culture (for exceptions, see Draper & Harpending, 1982; Gangestad &

Simpson, 1997). In practice, most evolutionary psychologists emphasize what

they believe is the relative uniformity of human sex differences across

individual and cultural variables (e.g., Archer, 1996; Buss, 1995b; Buss &

Kenrick, 1998; A. Campbell, in press), despite their frequent

acknowledgment that it is the interplay between evolved dispositions and

current environmental influences that produces behavior (e.g., Buss, 1996;

Tooby & Cosmides, 1990b). Evolutionary psychologists thus typically

emphasize "deeply rooted and universal human behavioral and cognitive

traits" (Foley, 1996, p. 195).

The aspect of evolutionary theory that has been applied most extensively to

sex differences is the theory of sexual selection initially proposed by

Darwin (1871) and further developed by Trivers (1972). In this view,

sex-typed features evolved through male competition, by which the

attributes of certain males fostered successful competition in dominance

contests with other males and thereby conferred a reproductive advantage on

these dominant males. Sex-typed features also evolved through females'

choice of mates, by which females selectively chose to mate with males who

displayed certain desirable attributes and thereby conferred a reproductive

advantage on these desirable males.

Because women constituted the sex that devoted greater effort to parental

investment, they were a limited reproductive resource for men, the less

investing sex (e.g., Buss, 1996). Differential investment occurred because

gestating, bearing, and nursing children restricted the number of children

that women could propagate during their lifespan, whereas men did not have

these restrictions. Men therefore competed for access to women, and women

chose mates from among the available men. As the more investing sex, women

were selected for their wisdom in choosing mates who could provide

resources or protection. Women's preferences for such men, in turn,

produced sexual selection pressures on men to satisfy these criteria.

According to popular theories of sexual selection in humans, sex

differences in parental investment established different rules for

reproductive success for men and women and consequently different adaptive

strategies (Buss, 1996; Kenrick, Trost, & Sheets, 1996). It was to men's

advantage in terms of fitness outcomes to "devote a larger proportion of

their total mating effort to short-term mating than do women" (Buss &

Schmidt, 1993, p. 205)-that is, to be relatively promiscuous. Women, in

contrast, benefitted from devoting a smaller proportion of their effort to

short-term mating and a larger proportion to long-term mating. Also,

because of women's concealed fertilization, men were unable to determine

easily whether a child was their biological progeny, who could then proffer

fitness gains. Men ostensibly adapted to this problem of paternity

uncertainty by exerting sexual control over women and developing sexual

jealousy and a motive to control women's sexuality (Daly & Wilson, 1988).

There was of course no parallel problem of maternity uncertainty that would

have induced women to exert sexual control over men.

According to contemporary evolutionary psychologists (e.g., Buss, 1995b;

Buss & Kenrick, 1998), sex differences in many psychological dispositions

arose from the conflict of interest that is displayed in the contrasting

sexual strategies of women and men. Because men competed with other men for

sexual access to women, men's evolved dispositions favor violence,

competition, and risk-taking. Women in turn developed a proclivity to

nurture and a preference for long-term mates who could support a family. As

a result, men strived to acquire more resources than other men in order to

attract women, and women developed preferences for successful, ambitious

men who could provide resources.

The assumption that ancestral humans living in the EEA had a

hunter-gatherer socio-economic system is critical to some of evolutionary

psychologists' claims about sex differences (e.g., Buss, 1995b; Cosmides et

al., 1992; DeKay & Buss, 1992). The idea of a division of labor by which

men hunted while women gathered suggests sex-differentiated pressures

linked to survival and reproduction. Such an ancestral division of labor

might have produced men who were psychologically specialized for hunting

and women who were specialized for gathering. For example, cognitive

abilities could have been affected, with men having the superior spatial

skills that followed from ancestral hunting, and women having the superior

spatial location memory that followed from ancestral gathering (e.g.,

Geary, 1995; Silverman & Eals, 1992; Silverman & Phillips, 1998).

According to this evolutionary perspective, virtually all human sex

differences are readily traced back to the different adaptive problems that

men and women are presumed to have faced during primeval history. Buss and

Kenrick (1998) thus described the evolutionary approach as a "metatheory"

of sex differences and similarities and summarized it as follows: "Men and

women differ in domains where they faced different adaptive problems over

human evolutionary history" (p. 994). These theorists thus derive human sex

differences from heritable adaptations built into the human species in the

EEA. Because these sex differences follow from evolutionary adaptations,

they are predicted to occur as central tendencies of male versus female

behavior. Human behavior would thus be characterized by a deep structure of

sex-differentiated dispositions, producing similar, albeit not identical,

behavioral sex differences in all human societies. Human social structure,

at least in its patriarchal aspects by which men dominate women, would be

an outcome of these evolutionary processes (e.g., B. Smuts, 1995).

Various mediating processes are implied in evolutionary psychology models

of behavioral sex differences. The first and most important involves some

means of retaining effective adaptations in human design and perpetuating

them over time. Thus, sex-differentiated psychological mechanisms and

developmental programs, like other organized, coordinated adaptations, are

"genetic, hereditary, or inherited in the sense that . . . their

structured design has its characteristic form because of the information in

our DNA" (Tooby & Cosmides, 1990a, p. 37; see also Buss, Haselton,

Shackelford, Bleske, & Wakefield, 1998; Crawford, 1998). Some evolutionary

accounts also emphasize that genetic factors trigger biochemical processes

that mediate psychological sex differences, especially by means of sex

differences in hormone production (e.g., Daly & Wilson, 1983; Geary, 1995,

1996; Goldberg, 1993). In addition, sex-typed evolved mechanisms are

translated into behavioral sex differences by various cognitive and

affective processes. Establishing these links requires theoretical

understanding and empirical documentation of the range of processes by

which the genetic factors implicated in innate dispositions might affect

human behavior. Although scientific understanding of these mediational

processes is essential to establishing the validity of the evolutionary

position, such mediation remains relatively uncharted territory (e.g.,

Collear & Hines, 1995).

Evaluation of the Evolutionary Origin Theory

A number of questions can be raised about evolutionary psychology's

account of the origins of sex differences. Some of these questions pertain

to the theory's assumptions about the environment of ancestral humans in

the Pleistocene era. Because adaptations evolved as solutions to past

environmental challenges, an understanding of human's primeval environment

is central to evolutionary theorizing. The ambiguity of scientific

reconstructions of the ancestral past leaves room for evolutionary

scientists to inadvertently transport relatively modern social conditions

to humans' remote past by inappropriately assuming that the distinctive

characteristics of contemporary relations between the sexes were also

present in the Pleistocene era.

To avoid biased reconstructions of the EEA, scientists should seek

independent evidence of the social and physical environments of ancestral

humans. Various bodies of science have some relevance, including

observational studies of other primates, the fossil record, and

ethnographic studies. Each form of scholarship includes sophisticated

theoretical arguments and technical analyses of the relevant data, and the

resulting views of how sex differences may have evolved do not always

coincide between these scientific literatures.

As we explain elsewhere (see Wood & Eagly, 1998), models of human nature

constructed from the behavior of non-human primates do not yield a uniform

picture that reflects key features of sex differences in modern human

societies (see also Travis & Yeager, 1991). Primatologists have noted

considerable variability in male-female relations across primate species

and within species in response to particular environmental conditions

(Fedigan, 1986; Hrdy, 1981; Strier, 1994). Among humans' genetically

closest relatives, bonobos and chimpanzees, male dominance hierarchies are

not primarily structured around access to females but instead are

multidimensional and vary with specific resources (e.g., access to food,

desirable locations).

Furthermore, individual males' positions in the dominance hierarchies

derive from a variety of factors, particularly social skills, and not

primarily from size or physical aggression (Strier, 1994). Bonobos' high

levels of sexual activity with both same-sex and mixed-sex partners (de

Waal, 1997) provides an especially striking contrast to many evolutionary

psychologists' assumptions about human sexuality (e.g., Buss & Schmidt,

1993).

Similarly ambiguous concerning sex differences are the models of early

human social conditions that paleontologists and paleoanthropologists have

developed from fossil evidence. Particularly troublesome to the

hunter-gatherer reconstruction of ancestral life that is popular with

evolutionary psychologists (e.g., Cosmides et al., 1992; Silverman & Eals,

1992) is the uncertain status of hunting during the Pleistocene era

(Johanson & Edgar, 1996). The available fossil evidence equally or more

strongly suggests scavenging groups (Potts, 1984) with only rudimentary

sex-typing of tasks (Rose & Marshall, 1996). Indeed, anthropological and

historical evidence indicates that simple foraging societies tended to be

relatively egalitarian and that strongly patriarchal social structures

developed as by-products of social and technological innovations (e.g.,

plough agriculture, animal husbandry) that appeared much later than the

Pleistocene era (e.g., Ehrenberg, 1989; Harris, 1993; Leibowitz, 1983;

Lerner, 1986; Sanday, 1981). In general, as social and technological

complexity increased in preindustrial societies, women's status fell

(Schlegel & Barry, 1986; Whyte, 1978).

Observations of more contemporary hunter-gatherer societies, albeit of

uncertain validity for revealing conditions that existed in the EEA, show

great variation in these societies' social organization (Foley, 1996;

Kelly, 1995). Although it is difficult to generalize about extent of male

dominance because dominance in one arena is not necessarily accompanied by

dominance in other arenas, male dominance does not appear to be culturally

universal. As Whyte (1978, p. 167) argued based on an extensive

cross-cultural study of preindustrial societies, "there is substantial

variation from societies with very general male dominance to other

societies in which broad equality and even some specific types of female

dominance over men exist." In summary, scientific efforts to reconstruct

the ancestral past from behavioral studies of primates, the fossil record,

and ethnographic research are not congenial to descriptions of ancestral

life as manifesting those features of male-female relations that are most

critical to the evolutionary psychological analysis (e.g., male effort to

control female sexuality, male dominance, a clear division of labor) (see

Wood & Eagly, 1998).

Given the ambiguity and complexity of scientific findings that might

clarify the adaptive problems that people would have faced in the EEA (see

Betzig, 1998), it is not surprising that there are many alternative

reconstructions of the social structures and reproductive arrangements of

that era. To quote Caporael and Brewer (1991, pp. 3-4), "Propositions

regarding ancestral social structures range from monogamous pair-bonds to

polygynous harems to female-offspring groups to male kin territorial

groups." For example, in an account that departs radically from typical

evolutionary assumptions about parental investment (e.g., Trivers, 1972),

Miller and Fishkin (1997) reasoned that ancestral environments would have

favored very strong male-female pair bonds and high levels of paternal as

well as maternal investment in offspring. Still other evolutionary models

emphasize the shared adaptive challenges faced by ancestral men and women

and argue that humans were likely selected for capabilities such as social

competence and the capacity for culture (see Fiske, Kitayama, Markus, &

Nisbett, 1998; Irons, 1979; MacDonald, 1991). For example, Caporael and

Brewer (1991, 1995) argued that, because small, cooperative groups

constituted ancestral social organization, the fitness gains of both sexes

would have been furthered by characteristics of sociality that promote

coordinated group functioning, such as cooperativeness, loyalty to the

group, and adherence to social norms (see also D. T. Campbell, 1983;

Caporael, 1997; Foley, 1996).

Another problematic issue in evolutionary psychologists' reasoning

concerns the stability of the EEA. Relevant to this issue is Tooby and

Cosmides' (1990b, p. 388) definition of the EEA as "the statistically

weighted composite of environmental properties of the most recent segment

of a species' evolution that encompasses the period during which its modern

collection of adaptations assumed its present form." Although Tooby and

Cosmides argued that this definition does not suggest that the EEA was

uniform or stable, except in a composite statistical sense, evolutionary

psychologists' assumption that evolution of the complex adaptations

relevant to human behavior was a very slow process seems to require

relative stability in the critical features that produced adaptations.

Consistent with this reasoning, Cosmides et al. (1992) maintained that the

considerable amount of time the human species spent in the EEA is evidence

that humans are adapted to this earlier environment and have not changed

appreciably since. Specifically, "the few thousand years since the

scattered appearance of agriculture is only a small stretch in evolutionary

terms, less than 1% of the two million years humans' ancestors spent as

Pleistocene hunter-gatherers. For this reason, it is unlikely that new

complex designs . . . could evolve in so few generations" (p. 5).

In a contrasting view that does not assume any particular pace of

evolutionary response to environmental change, D. S. Wilson (1994) has

argued that evolution is a variable process that depends on factors such as

the intensity of selection, the heritability of traits, and the number of

generations exposed to the evolutionary pressure. Although scientists do

not yet have detailed understanding of the intensity of selection pressures

on humans or the heritability of trait adaptations and nonadaptations,

scientists have shown that evolution can proceed quickly in at least some

species under appropriate conditions (e.g., Grant & Grant, 1993; Weiner,

1994; Zimmerman, 1960) and that some human traits (e.g., the production of

lactase in adulthood and the sickle-cell trait) appeared after the end of

the Pleistocene era (Durham, 1991). Also, Sarich (1997) has argued that the

human racial (i.e., regional) differentiation that is observed today

resulted from changes that occurred in the last 15,000 or so years. As

other scholars have also concluded (e.g., Irons, in press), such claims

raise doubts about the extent to which heritable human psychological traits

were fixed in the Pleistocene era.

Inferring what composites of environmental properties might have been

relevant to selection is difficult, given the abundant changes that

occurred in the human species and its environments during the Pleistocene

era. During the two million years during which human beings were ostensibly

Pleistocene hunter-gatherers (Cosmides et al., 1992), several different

hominid species appeared and disappeared (Irons, in press). It is likely

that a wide variety of foraging groups existed during this time (Foley,

1996) and that these different groups were exposed to extremely diverse

types of adaptive problems (Simpson, 1995). Recurrent ice ages brought

radical shifts in climate and ecology. Furthermore, early homo sapiens

immigrated over the globe from their origins in Africa (Johanson & Edgar,

1996)-a transition that exposed them to varying geographical, climatic, and

ecological environments and likely required considerable shifts in social

organization (Foley, 1996).

Even greater difficulty in identifying stable contingencies of selection is

posed by the recognition that the adaptations characteristic of humans did

not co-evolve simultaneously (Foley, 1996; Lovejoy, 1981). For example,

bipedalism appears to have emerged with Australopithecines, well before

documented tool use and human-like encephalization. According to Tooby and

DeVore (1987), "any substantial change in a major socioecological variable

may reorganize the relationship of many of the others, causing payoffs of

other activities to change markedly, and labile components of adaptive

configurations to alter abruptly" (pp. 205-206). Consequently, the

emergence of each human attribute might have changed a variety of aspects

of hominid life and yielded uniquely structured social organizations

functional only for limited periods of time.

In sum, evolutionary psychologists' argument that humans possess a large

number of universally shared, highly specialized, sexually dimorphic

adaptations requires tenuous assumptions about the rate of human adaptation

and the stability of the contingencies of selection in the EEA. Little

evidence supports the claim that humans as a species evolved during this

earlier period but have not evolved appreciably since or the claim that the

EEA presented consistently structured but sex-differentiated evolutionary

pressures. To the extent that the Pleistocene established the environment

that "defined the adaptive problems the mind was shaped to cope with"

(Cosmides et al., 1992, p. 5), we maintain that the mind should be shaped

to cope flexibly with a very wide range of changing conditions.

In addition to these concerns about the nature and stability of the EEA,

questions can be raised about how evolutionary psychologists go about

identifying the psychological mechanisms and other adaptations in humans.

As illustrated by the work of scholars such as Buss (1995a), Tooby and

Cosmides (1992), and Symons (1992), evolutionary psychologists identify

adaptations by relying "on informal arguments as to whether a presumed

function is served with sufficient precision, economy, efficiency, etc. to

rule out pure chance as an adequate explanation" (Williams, 1966, p. 10).

To identify the function of biological mechanisms, evolutionary

psychologists assume "that functional design is something that can be

intuitively comprehended by an investigator and convincingly communicated

to others" (Williams, 1996, p. 260). Evolutionary explanations that reflect

this approach consist of an informal analysis of the functional relations

served by a particular psychological mechanism along with the construction

of a convincing story about how the adaptation might have made an efficient

contribution to genetic survival or some other goal contributing to

reproduction (Gould, 1980; Williams, 1966). Brandon (1990, p. 180) labeled

these functional analyses "speculative how-possibly explanations," and

Caporael (1997, p. 295) warned against these analyses' pitfalls of

"confirmatory biases, the seductiveness of scenario-thinking, the problems

posed by the availability and representativeness heuristics, and the

biasing effects of vividness in descriptions of the past."

Given the reliance of this method on scientists' insights about functions,

special difficulties arise in distinguishing adaptations from several other

products of evolution postulated by evolutionary scientists-namely, from

(a) features that originally had utility for one function but were

subsequently co-opted to fulfill a new function, (b) features that were

originally mere by-products of adaptations but may or may not have been

subsequently co-opted to fulfill a function, and (c) features that were

random and thus did not initially evolve to fulfill a function but may or

may not have been subsequently co-opted to fulfill a function (see Buss et

al., 1998; Gould, 1991; Williams, 1966). These more refined distinctions

considerably complicate the task of formulating hypotheses about the

evolutionary origins of behavior, because particular benefits to the

organism hypothesized for early or subsequent environments do not provide a

clear-cut basis for identifying evolved mechanisms. Moreover, the products

of evolution must be distinguished from the products of cultural change.

Behaviors that provide efficient engineering solutions to problems of

reproduction and survival can arise from inventive trial-and-error among

individuals who are genetically indistinguishable from other members of

their living groups; such beneficial behaviors are then imitated and

transmitted culturally. Despite these complexities, Tooby and Cosmides

(1990b, p. 401) proposed that "every behavior, adaptive or maladaptive, is

the product of adaptations (or other linked aspects of underlying design)

and hence is patterned by the structure of these adaptations." Given such a

viewpoint, it is not surprising that specialized mechanisms have

proliferated in current evolutionary models. If the result is a long list

of adaptations, each applicable in its own domain, this proliferation

becomes reminiscent of some of the pitfalls of earlier instinct theories.

The most convincing evidence that a behavioral pattern reflects an

adaptation would be that individuals who possessed the adaptation enjoyed a

higher rate of survival and reproduction than individuals who did not

possess it. However, such evidence is difficult, if not impossible, to

produce. Because evolved mechanisms in humans emerged in relation to past

selection pressures, present reproductive advantage does not necessarily

reflect past advantage, and evolutionary psychologists have warned against

relying on measures of current reproductive success to validate postulated

adaptations (Buss, 1995a; Tooby & Cosmides, 1992). Despite these

reservations, it is not uncommon to find evolutionary psychologists

invoking current fertility data to validate evolutionary claims and even

arguing that such evidence can be persuasive (Betzig, 1998). For example,

to support the ideas that men invested less in offspring than women and

that a strategy emphasizing quantity of sexual partners was adaptive for

men, Buss (1996) cited data from a contemporary foraging society in which

the variance in number of children is higher among men than among women

(see also Perusse, 1993). In our view, it is reasonable to conclude that

modern fertility data provide uncertain evidence for adaptations, given

that past adaptations are not necessarily functional in current society.

This uncertainty is part of the broader intellectual predicament that

follows from the intuitive identification of what might have been adaptive

for ancestral humans and from the analysis of how these postulated

adaptations might interact with current environmental factors to generate

behavior.

Social Structural Theory as an Origin Theory of Sex Differences

Most social scientists locate the ultimate cause of sex differences, not

in evolved psychological dispositions that are built into the human psyche,

but in the contrasting social positions of women and men. In contemporary

American society, as in many world societies, women have less power and

status than men and control fewer resources. This feature of social

structure is often labeled gender hierarchy or in feminist writing it may

be called patriarchy. In addition, as the division of labor is realized in

the United States and many other nations, women perform more domestic work

than men and spend fewer hours in paid employment (Shelton, 1992). Although

most women in the United States are employed in the paid workforce, they

have lower wages than men, are concentrated in different occupations, and

are thinly represented at the highest levels of organizational hierarchies

(Jacobs, 1989; Reskin & Padavic, 1994; Tomaskovic-Devey, 1995). From a

social structural perspective, features of social organization, in

particular gender hierarchy and the sexual division of labor, are the root

cause of sex-differentiated behavior.

The determinants of the distribution of men and women into social roles are

many (see Wood & Eagly, 1998) and include the biological endowment of women

and men. The sex-differentiated physical attributes that influence role

occupancy include men's greater size and strength, which would give them

priority in nonmechanized warfare and in jobs involving certain types of

strenuous activity, especially involving upper body strength. These

considerations of men's greater size and strength are less important in

societies in which few occupational roles demand these attributes, such as

post-industrial societies in particular. Also important in relation to role

distributions are women's childbearing and in many societies their activity

of lactating for long periods of time; these obligations would give them

priority in roles involving the care of very young children and conflict

with roles that require extended absence from home and uninterrupted

activity. These considerations of women's reproductive activity are less

important in societies with low birthrates, less reliance on lactation for

feeding infants, and greater reliance on nonmaternal care of young

children. Thus, physical sex differences, in interaction with other

variables, influence the roles held by men and women (see Wood & Eagly, 1998).

The differing distributions of men and women into social roles form the

basis for a social structural metatheory of sex differences, just as

evolutionary theory provides a metatheory. The major portion of the social

structural theory follows from the typical features of women's roles versus

men's. Thus, the first metatheoretical principle derives from the greater

power and status that tends to be associated with male-dominated roles and

can be succinctly stated as follows: Women's adaptations to roles with

lesser power and status in society produce a pattern of behavior that

might be described as subordinate, and men's adaptations to greater power

and status produce more dominant behavior (Ridgeway & Diekema, 1992; P.

Stewart, 1988). Subordinate behavior is more compliant to social influence,

less overtly aggressive, and more cooperative and conciliatory. Dominant

behavior is controlling, assertive, relatively directive and autocratic,

and may involve sexual control. In this view, men's sexual control over

women is but one example of male dominance.

The second metatheoretical principle follows from the differing balance of

activities associated with the typical roles of each sex. Women and men

seek to accommodate sex-typical roles by acquiring the specific skills and

resources linked to successful role performance and by adapting their

social behavior to role requirements. A variety of sex-specific skills and

beliefs arise from men's and women's typical family and economic roles,

which in many societies can be described as resource provider and

homemaker. Women and men seek to accommodate to these roles by acquiring

role-related skills, for example, women learning domestic skills such as

cooking and men learning skills that are marketable in the paid economy.

The social behaviors associated with these roles have been characterized in

terms of the distinction between communal and agentic characteristics

(Bakan, 1966; Eagly, 1987). Thus, women's accommodation to the domestic

role and to female-dominated occupations produces a pattern of

interpersonally facilitative and friendly behaviors that can be termed

communal. In particular, the assignment of the majority of child-rearing to

women encourages communal behaviors, including nurturant behaviors that

facilitate care for children and other dependent individuals. The

importance of close relationships to women's nurturing role favors the

acquisition of superior interpersonal skills and ability to communicate

nonverbally. In contrast, men's accommodation to the employment role,

especially to male-dominated occupations, produces a pattern of assertive

and independent behaviors that can be termed agentic (Eagly & Steffen,

1984). This argument is not to deny that paid occupations show wide

variation in the extent to which they favor more masculine or feminine

qualities. Suggesting that sex-differentiated personal qualities may be

shaped by paid occupations are demonstrations that to the extent that

occupations are male-dominated, success in them is perceived to follow from

agentic personal qualities, whereas to the extent that occupations are

female-dominated, success in them is perceived to follow from communal

personal qualities (Cejka & Eagly, in press; Glick, 1991).

In summary, two metatheoretical principles of sex differences follow from

the contrasting positions of men and women in the social structure: One

principle invokes the greater status that is typical of men's roles, and

the second principle recognizes the differing types of activities that are

typical of women's versus men's roles, which in many societies reflect

resource provider and homemaker roles. Although these principles provide a

general account of virtually all human sex differences, understanding their

variability across situations and individuals requires additional

principles (e.g., Deaux & Major, 1987).

Although the differing assignments of women and men to social roles are

considered to be the basic underlying cause of sex-differentiated social

behavior, their impact on behavior is mediated by psychological and social

processes. One statement of mediational links is in social role theory

(Eagly, 1987; Eagly & Wood, 1991), which implicates gender roles as a

proximal cause of sex differences. By this account, differential role

occupancy fosters gender roles by which each sex is expected to have

characteristics that equip it for its sex-typical roles. Because gender

roles encompass desirable as well as typical attributes of men and women,

the attributes that are thought to be desirable and appropriate to women

and men depend on the activities that each sex is expected to perform.

The expectancies associated with gender roles act as normative pressures

that foster behaviors consistent with sex-typical work roles. Gender roles

are emergents from the productive work of the sexes; the characteristics

embodied in these roles become stereotypic of women or men. To the extent

that women more than men occupy roles that demand communal behaviors,

domestic behaviors, or subordinate behaviors for successful role

performance, such tendencies become stereotypic of women and are

incorporated into a female gender role. To the extent that men more than

women occupy roles that demand agentic behaviors, resource acquisition

behaviors, or dominant behaviors for successful role performance, such

tendencies become stereotypic of men and are incorporated into a male

gender role. Gender roles facilitate the activities typically carried out

by people of each sex. For example, the expectation that women be

other-oriented and compassionate facilitates their nurturing activities

within the family as well as their work in many female-dominated

occupations (e.g., teacher, nurse, social worker).

To the extent that these normative expectations about behavior appropriate

to women and men become internalized as part of individuals' self-concepts

and personalities, people can be described as forming dispositions or

traits that are consistent with gender roles (Feingold, 1994; Wood,

Christensen, Hebl, & Rothgerber, 1997).Yet, people may also behave

consistently with their gender roles without necessarily acquiring

dispositions that foster such behavior. Congruent with empirical research

on the behavioral confirmation of stereotypes and other expectancies (see

Olson, Roese, & Zanna, 1996), people communicate gender-stereotypic

expectations in social interaction and can directly induce the targets of

these expectations to engage in behavior that confirms them (e.g., Skrypnek

& Snyder, 1982; Wood & Karten, 1986).

Gender roles, viewed as shared expectations that apply to individuals on

the basis of their socially identified sex (Eagly, 1987), co-exist with

specific roles based on factors such as family relationships (e.g., mother,

son) and occupation (e.g., secretary, firefighter). Role theorists maintain

that, because specific social roles are very constraining, sex differences

would tend to erode when men and women occupying the same specific social

role are compared (e.g., Eagly & Johnson, 1990). However, gender roles

ordinarily continue to have some impact on behavior, despite the

constraints of specific roles. For example, Gutek and Morasch (1982) argued

that gender roles spill over to workplace roles and cause people to have

different expectations for female and male occupants of the same workplace

role. Moreover, experimental evidence (e.g., Hembroff, 1982) suggests that

people combine or average the expectations associated with specific roles

and more diffuse roles such as gender roles in a manner that weights each

set of

expectations according to its relevance to the task at hand.

The social structural perspective provides a broad theoretical outline

within which many social scientific theories of sex-differentiated behavior

can be placed. These theories focus on different aspects of the processes

by which societies produce sex-differentiated behavior, and many theories

have spawned detailed predictions and a substantial body of empirical

research (see Beall & Sternberg, 1994; Canary & Dindia, 1998; England &

Browne, 1992). For example, developmental psychologists have studied

socialization in the family, school, and peer group. Social psychologists

have examined the impact of gendered self schemas, men's greater status,

sex-differentiated expectations about behavior, and gendered patterns of

social interaction. Sociologists have implicated organizational factors

such as discriminatory employment practices, societal factors such as men's

greater ownership of capital, and cultural factors such as the ideologies

that legitimize gender inequality. Social scientists have thus provided an

array of interrelated theories, each of which illuminates certain aspects

of the complex of processes by which sex-differentiated behavior is produced.

In sum, in social structural accounts, women and men are differently

distributed into social roles, and these differing role assignments can be

broadly described in terms of a sexual division of labor and gender

hierarchy. This division of labor and the patriarchal hierarchy that

accompanies it provide the engine of sex-differentiated behavior because

they trigger social and psychological processes by which men and women seek

somewhat different experiences in order to maximize their outcomes within

the constraints that societies establish for people of their sex. Sex-typed

social roles are the underlying determinants of men's and women's social

behavior, but the impact of these roles is mediated by social and

psychological processes. The essential idea of this approach is the

functional principle that people come to expect that women and men possess

those characteristics that allow them to carry out their sex-typical

productive work. Because sex differences are adjustments to the differing

restrictions and opportunities that a society provides for its men and

women, the differences that are observed today reflect existing social

conditions and thus are thoroughly modern.

Evaluation of the Social Structural Origin Theory

A number of criticisms have been leveled against the social structural

theory of sex differences and more specifically against social role theory

(see Archer, 1996; Buss, 1996). At least some evolutionary psychologists

have expressed skepticism in some of their writings that culture and social

structure could have any causal role at all in relation to sex differences.

Culture and social structure are seen as abstractions that cannot be

responsible for behavioral differences, and causation is judged unclear or

implausible when it is located in factors such as men's and women's

differing social roles. For example, Buss (1995a) wrote, "'culture,'

'learning,' and 'socialization' do not constitute explanations, let alone

alternative explanations to those anchored in evolutionary psychology" (p.

14). In contrast, the great majority of social scientists have no

difficulty whatsoever in accepting culture and social structure as causal

in relation to human behavior. Culture is often thought to exist separately

from genetic evolution (e.g., D. T. Campbell, 1975), although theories of

gene-culture coevolution treat culture as interdependent with genetic

evolution (e.g., Barker, 1989; Durham, 1991). Culture, as knowledge,

beliefs, and evaluations shared among members of a society, and social

structure, as "persisting and bounded patterns of behavior and interaction

among people or positions" (House, 1995, p. 390), can be held causally

responsible for the content of social roles. Social roles, which are

themselves social constructions, can induce behavior because they foster

role-appropriate responding through a variety of more proximal mechanisms.

Another criticism is that in social structural theories, individuals are

treated as mere passive receptacles of the roles they are assigned (Buss,

1996). Although social scientists often do refer to people as "assigned" to

roles, the processes by which role assignment occurs are not necessarily

passive. On the contrary, social and organizational psychologists have

demonstrated that these processes are complex and dynamic (e.g., Kerckhoff,

1995). Organizations, for example, must initially select appropriate

entry-level candidates for organizational roles from among persons who seek

out these roles. Organizations establish systems for teaching and

maintaining appropriate role behavior; individuals within organizations

continually adjust their role performance based on performance feedback,

others' expectations, and their own goals (see Pfeffer, 1998). In deciding

whether to attempt to assume particular roles at all, individuals take

their own attributes, skills, and personal preferences into account,

although in some cultural contexts some roles are imposed on people

regardless of their own preferences (e.g., the practice of early betrothal

of girls). Yet, roles are not typically assigned to individuals

arbitrarily, as if they were passive actors in the social system. Rather,

social systems are arranged to shape people's self-concepts, skills,

beliefs, and values so that the majority of people actively seek out

experiences that help them to become appropriate occupants of existing

social roles by meeting the expectations of these roles. The active nature

of role assignment becomes apparent when some individuals fail to master

even the society's most basic roles. For example, Bernard (1981) provided

poignant descriptions of men who failed to accommodate successfully to the

role of provider in its heyday and dropped out to become tramps or hobos.

Evolutionary psychologists also criticize gender roles as "essentially

arbitrary" (Buss, 1996, p. 19) or as arising by "historical accident"

(Archer, 1996, p. 915). This perception of arbitrariness fails to take into

account that gender roles are very firmly rooted in a society's division of

labor. The content of gender roles is not arbitrary but is determined by

the social system, economy, and shared cultural beliefs. Roles must thus

facilitate the economic endeavors of a society, if its members are to

prosper and survive. Therefore, different types of role systems become

effective under differing circumstances. For example, in industrial

economies, many roles are organized by a market pricing system that takes

into account factors such as ownership of property and contribution to

production (see Fiske, 1992). Psychologists who adopt a social structural

perspective do not themselves provide a theory of how and why social

organization changes over time. Instead, appropriate analytical frameworks

have been developed by scholars in other disciplines (e.g., Diamond, 1997;

Toynbee, 1931-1961). However, understanding the principles by which women

and men distribute themselves into a society's roles is part of the agenda

of social psychologists (Wood & Eagly, 1998) as well as other social

scientists (e.g., Ehrenberg, 1989; Harris, 1993; Lerner, 1986; Sanday,

1981). Moreover, the structurally oriented social psychologist assumes

that, whatever a society's role system is, social and psychological

processes ensue by which the majority of people accommodate themselves to it.

A related criticism is that, from a social structural perspective,

"differences between cultures are random with respect to evolutionary

hypotheses and therefore that, for example, sex differences should occur as

frequently in one direction as the other" (Tooby & Cosmides, 1989, p. 37).

However, social structuralists would not predict random variation in sex

differences across societies. As Wood and Eagly (1998) outline, variation

in the roles of men and women across societies depend on a variety of

factors, including men's greater physical strength, women's reproductive

activities, and the activities required by a society's economy and social

organization, which in turn reflect technological developments and the

current ecology. Because these factors that underlie sex-typed social

structures are not randomly distributed, certain types of social

arrangements are more common than others, and sex differences appropriate

to the common arrangements should be more frequent than reversals of these

differences. The social structuralist would go further and predict the

conditions under which differences would appear and disappear (see

subsequent discussion of mate selection).

Another criticism of the social structural approach is that it treats the

minds of women and men as identical except by virtue of the constraints

that follow from externally assigned roles (Buss, 1996). While believing

that the issue of whether female and male brains are intrinsically

different is best addressed by scientific research, we acknowledge that a

purely social structural perspective does indeed maintain that differences

in the minds of women and men arise primarily from experience and

socialization. Moreover, the diversity of behaviors and skills exhibited by

men and women across societies and within societies suggests that in most

domains humans' attributes are extremely plastic and minimally constrained

by initial, intrinsic sex differences. Yet, this perspective is fully

compatible with the idea that people possess evolved facilities, such as

for language, that develop in predictable ways in appropriate environments.

The typical social structuralist begins with the assumption that the great

majority of these basic psychological facilities are the same in women and

men and that the placement of each sex in the social structure of a given

society molds behavior into sex-differentiated patterns.

Sex Differences Predicted from

Evolutionary Psychology and Social Structural Theory

All theories of sex-differentiated behavior should be evaluated by their

ability to predict the differences and similarities between female and male

behavior. Social structural theories of sex differences are associated with

predictions about a wide range of social behaviors (e.g., social influence,

social interaction, prosocial and antisocial behavior, nonverbal behavior,

leadership). Because most of these behaviors have not been studied

extensively from an evolutionary perspective, they do not provide an

appropriate ground for comparing the two approaches. The most reasonable

area for this comparison of theories is human mating behavior, especially

sex differences in mate selection criteria. Evolutionary predictions have

been articulated especially clearly for mating activities, and, as we

explain below, these behaviors can also be used to test a social structural

perspective. Furthermore, empirical findings concerning the mate selection

preferences of men and women have been well established for many years in

the literature on the sociology of the family (e.g., Coombs & Kenkel,

1966). Powers' (1971) summary of 30 years of prior research concluded that,

at least in the United States, women generally prefer mates with good

earning potential, whereas men prefer mates who are physically attractive

and possess good domestic skills. Furthermore, women typically prefer a

mate who is older than them, whereas men prefer a mate who is younger.

Feingold's (1991, 1992a) meta-analyses established that the sex differences

in valuing potential mates' earning potential and physical attractiveness

are robust. Subsequent research, notably Sprecher, Sullivan, and Hatfield's

(1994) excellent study of a national probability sample of single adults,

provided further confirmation of the sex differences in age preferences as

well as in valuing earning potential and physical attractiveness (but see

mixed evidence in Regan & Berscheid, 1997).

Evolutionary Models of Mate Preference

Modern evolutionary psychologists have adopted mate preferences as

signature findings of their analysis. Women's valuing of mates' resources

and men's valuing of mates' youth and physical attractiveness are thought

to arise from the different parental investment of the sexes that was

outlined in Trivers' (1972) sexual selection theory. It is commonly argued

that women, as the more investing sex, seek mates with attributes to

support their parenting efforts. However, human mate selection does not

follow a strict version of Trivers' (1972) males-compete-and-females-choose

model, because among humans selection is a product of the behavior of both

sexes (a process Darwin [1871] called "dual selection"). In Buss's (1989a)

account, men's preferences derive from the additional dynamic that, because

of women's time-limited reproductive capacity, men seek mates with

attributes that suggest they possess such capacity. Yet, to the extent that

human mating conforms to Trivers' theory and that women are the more

investing sex, women's preferences should be the primary selective force in

human mating, and men's preferences should be less important. In an

analysis that builds on sexual selection theory yet accords male and female

preferences relatively equal weight, Kenrick and Keefe (1992) suggest that

human males and females both invest heavily in offspring and are selective

about potential mates but that the sexes invest different kinds of

resources. This resource differential is thought to underlie sex

differences in mate preference. In particular, "men invest relatively more

indirect resources (food, money, protection, and security), and females

invest relatively more direct physiological resources (contributing their

own bodily nutrients to the fetus and nursing the child)" (Kenrick & Keefe,

1992, p. 78). As a result, women prefer mates who can provide indirect

resources, and men prefer healthy mates with reproductive potential.

Despite this general consensus among contemporary evolutionary

psychologists about the qualities women and men prefer in mates, a broader

sampling of evolutionary scientists' writings reveals considerable

variability in their opinions. For example, E. O. Wilson (1975, p. 569)

argued that women's choices would be directed toward "hunting prowess,

leadership, skill at tool making, and other visible attributes that

contribute to the success of the family and the male band." In contrast,

Darwin (1871) thought that women in primeval times chose men who were

handsome defenders and providers; "women would generally choose not merely

the handsomest men, according to their standard of taste, but those who

were at the same time best able to defend and support them" (Darwin, 1871,

p. 585). Darwin expressed skepticism, however, about how applicable the

processes of sexual selection are to modern human societies. He argued that

sexual selection was more powerful among early humans, who were guided by

instinctive passions, than among contemporary members of society, who show

greater foresight and reason in mating behavior. In fact, Darwin (1871)

maintained that "civilized men are largely attracted by the mental charms

of women, by their wealth, and especially by their social position" (p. 178).

From a comparative perspective on sexual selection, preference for

resources is likely to depend on a variety of contextual factors, including

the pattern of resources controlled by each sex in a community (R. W.

Smuts, 1989). In human societies in which most of the resources are

controlled by men, women are more likely than men to prefer mates with

resources. In contrast, among nonhuman primates, females usually support

themselves and their young with little male

help, and in hunter-gatherer societies and many agricultural societies,

women do a great deal of the productive work and supply many of the

economic resources for their families. Although Smuts's views remain

controversial (see Buss, 1991), he suggested that, given these social

organizations, there are "strong reasons to suspect that a preference for

economically successful mates might have a bigger genetic payoff for males

than for females" (R. W. Smuts, 1989, p. 33).

Social Structural Models of Mate Preferences

From a social structural perspective, women and men are sought after as

mates to the extent that they are suited to fulfill the marital roles of

their society. The critical assumption about the underlying psychology of

mate selection is merely that people attempt to maximize their utilities

with respect to mating choices, just as they do with respect to other

decisions. Consistent with these ideas, Becker's (1976) economic analysis

of mating decisions characterized marriage as occurring between

utility-maximizing men and women who can reach an equilibrium with a

variety of types of exchanges, including, for example, an exchange between

men's wages and women's contributions in terms of household production and

other attributes such as education and beauty. This cost-benefit analysis

of mating appears even on occasion in the writings of evolutionary

scientists. For example, Tattersall (1998, p. 207) maintained that

behavioral regularities such as sex differences in mate selection criteria

are as likely due to "rational economic decisions" as inherited

predispositions, and Hrdy (1997, p. 29) wrote that "a woman's preference

for a wealthy man can be explained by the simple reality that in such

societies males monopolize ownership of productive resources."

The outcomes that are perceived to follow from mating decisions depend on

the marriage and family arrangements that exist within this structure. To

the extent that women and men occupy marital and family roles that entail

distinctively different responsibilities and obligations, they should

select mates according to criteria that reflect these divergent

responsibilities and obligations. Consider, for example, the family system

based on a male provider and a female domestic worker. This system became

common in industrial economies and is still prevalent in many world

societies. According to Bernard (1981), in the United States these roles

arose approximately in the 1830s. This male provider system remained

dominant in the United States until the 1970s, and its gradual and

continuing demise was marked in 1980 by the abandonment by the U.S. Census

of the practice of automatically declaring the male the head of the

household. To the extent that societies have a division of labor between

female domestic responsibility and male contribution to the economy, women

maximize their outcomes by seeking a mate who is likely to be successful in

the economic, wage-earning role. In turn, men maximize their outcomes by

seeking a mate who is likely to be successful in the domestic role.

The sex differences in the preferred age of mates also can be understood

as part of the general tendency of men and women to seek a partner likely

to provide a good fit to their society's sexual division of labor and

system of marital roles. Specifically, the marital system based on a male

breadwinner and a female homemaker favors the age gap in marriage. In

general, marriageable women who are younger than their potential mates have

lesser wages, social status, and education and knowledge than women who are

the same age. With the combination of a younger, less experienced woman and

an older, more experienced man, it would be easier to establish the power

differential favoring men that is normative for marital roles defined by a

male breadwinner and a female domestic worker (Lips, 1991; Scanzoni &

Szinovacz, 1980; Steil, 1997). Moreover, assuming that women, as

utility-maximizing individuals, act to maximize their perceived outcomes,

younger women are more likely to view marriage as a good outcome, compared

with alternative life situations, and are more likely to accept the role of

domestic worker in a marriage. In complementary fashion, older men are more

likely to have acquired the economic resources that make them good

candidates for the provider role. The older man and younger woman thus fit

more easily than same-age partners into the culturally expected pattern of

good provider and skillful domestic worker.

Cross-Cultural Evidence for Sex Differences in Mate Preferences

The modern evolutionary psychology predictions that women select for

resources and older age and men for attractiveness and younger age have

received support from cross-cultural studies of mate preference (Buss,

1989a; Buss et al., 1990; Kenrick & Keefe, 1992). Buss's impressive study

in 37 cultures of the characteristics that people desire in mates suggested

that, consistent with evolutionary perspectives, these sex differences in

mate preferences emerge cross-culturally (Buss, 1989a; Buss et al., 1990).

Also, Kenrick and Keefe (1992) examined age differences in mates in five

countries and across various time periods in the twentieth century and

concluded that all provided evidence of sex-related age preferences in

mates. Specifically, for dating and marriage, women prefer older men and

men prefer younger women, although men's preference for younger age is

moderated by men's age, with teenage boys preferring same-aged girls.

Based on these investigations, evolutionary accounts have emphasized the

cross-cultural commonality in women's preference for resources and older

age and men's for attractiveness and youth. According to Buss (1989a) and

Tooby and Cosmides (1989), uniformity across diverse cultures and social

circumstances suggests powerful sex-differentiated evolved mechanisms that

reflect an innate, universal human nature. Kenrick and Keefe (1992)

similarly argued that "invariance across cultures is evidence that supports

a species-specific, rather than a culture-specific, explanation" (p. 76).

Despite evidence for cross-cultural commonality, these investigations also

yielded evidence for cultural variation in sex differences in mate

selection criteria. For example, Kenrick and Keefe (1992) found that the

preference for younger wives was evident among Philippine men of all ages,

but only among older (i.e., 30+) men in the United States. It is not

useful, however, to debate whether these studies yielded mainly

cross-cultural uniformity or variability. The simple existence of

uniformity or variability does not provide a definitive test of either the

evolutionary or the social structural origin theory. Although evolutionary

psychologists emphasize uniformity and social structural theorists

emphasize variability, both perspectives have some power to explain both of

these cross-cultural patterns. To account for uniformity, social

structuralists can point to similarities in the sexual division of labor in

the studied societies and argue that these produce comparable sex

differences across societies. In particular, despite the fact that Buss et

al. (1990) and Kenrick and Keefe (1992) produced the most cross-culturally

comprehensive findings that are available concerning mate preference, they

did not sample world societies in representative fashion. As Buss (1989a)

noted, his 37 cultures were biased toward urbanized cash-economy cultures,

with 60% from Europe and North America. Furthermore, respondents selected

from each society tended to be young, comparatively well-educated, and of

relatively high socio-economic status. To the extent that these societies

share features linked to the definitions of men's and women's roles and to

the extent that the respondents were similarly placed in these societies'

social structures, commonality in the sex differences that follow from

social structure should characterize these societies.

To account for cross-cultural variability, both evolutionary and social

structural origin theories recognize that developmental processes and

social factors that are unique to each society direct behavior in ways that

can yield variability in sex differences across cultures. Beyond this

insight that some evidence of cross-cultural variability would not surprise

theorists in either camp, the particular pattern of cross-cultural

variation provides an informative test of the mechanisms underlying sex

differences. Specifically, the social structural argument that the sexual

division of labor within a given society is responsible for sex differences

in social behavior yields predictions concerning cross-cultural variability

in mate preferences.

In the nations included in Buss et al.'s (1990) cross-cultural sample,

whose economies range from agrarian to post-industrial, some cultures would

still be strongly marked by this division of labor between the provider and

domestic worker, whereas other cultures have departed from it. In advanced

economies like the United States, women have entered the paid labor force

and spend a smaller proportion of their time in domestic labor (Haas, 1995;

Shelton, 1992). Although the tendency for men to increase their hours of

domestic work is much more modest, the lives of men and women become more

similar with greater gender equality. Therefore, people of both sexes

should lessen their emphasis on choosing mates whose value is defined by

their fit to the division between domestic work and earning in the wage

economy. Even in post-industrial economies such as the United States,

however, the sex-typed division of labor remains in modified form, with men

devoting longer hours than women to wage labor and women devoting longer

hours to domestic work (e.g., Ferree, 1991; Presser, 1994; Shelton, 1992).

Therefore, the social structural prediction is that the sex differences in

mate selection criteria that follow from the male-female division of labor

should be substantially weakened in societies characterized by greater

gender equality, albeit still present to the extent that complete equality

has not been achieved.

Some support for this social structural interpretation was provided in

Glenn's (1989) reanalysis of Buss and colleagues' (1990) 37 cultures data,

which examined whether the sex differences in mate preferences at a

societal level varied with indexes of economic development. Although in

more developed countries both sexes placed less importance on financial

prospects and preferred a smaller age difference between self and spouse,

the relationships to sex differences in provider characteristics were

nonsignificant. However, because development is only a proxy for equality

of the sexes, Glenn's test of the social structural hypothesis must be

regarded as preliminary. In another effort, Buss (1989a) correlated A. J.

Stewart and Winter's (1977) indexes of gender equality with societies' mean

sex difference in the value assigned to earning capacity in a subsample of

30 of the 37 cultures. Although these correlations were nonsignificant, the

reduced sample as well as possible limitations of the Stewart and Winter

indexes led us to believe that it would be worthwhile to produce a more

thorough test of the hypothesis that sex-typed preferences for mates lessen

with greater structural equality between the sexes.

Reanalysis of Buss et al.'s (1990) 37 Cultures Data

We reanalyzed Buss and his colleagues' (1990) 37 cultures data to evaluate

whether the division of labor within a society could explain the mate

preferences of men and women. Buss et al. (1990) examined samples of young

people in 37 cultures drawn from 33 countries that were widely dispersed

around the world. In each culture, two questionnaire measures assessed

preferences for a wide range of characteristics that might be desired in

mates: (a) one instrument obtained rankings of a set of 13 characteristics

according to "their desirability in someone you might marry"; (b) the other

instrument obtained ratings on a 4-point scale of each of 18

characteristics on "how important or desirable it would be in choosing a

mate" (Buss et al., 1990, p. 11). Buss and his collaborators represented

each culture by men's and women's mean ranking of each of the 13 mate

selection criteria and mean rating of each of the 18 criteria.

Our reanalysis confirmed Buss et al.'s (1990) conclusion that women placed

more value than men on a mate's wage-earning ability. Furthermore,

consistent with the greater domestic responsibility of women than men in

most cultures, the data also showed that men valued good cook and

housekeeper more than women did, a sex difference that has received little

attention from evolutionary psychologists. When averaged across the 37

cultures, this sex difference was of comparable magnitude to that obtained

on attributes emphasized by evolutionary psychologists. Specifically, in

Buss et al.'s (1990) ranking data, good earning capacity produced the

largest sex difference among the 13 criteria, followed by physically

attractive in second place, and good housekeeper in third place. In the

rating data, financial prospect produced the largest difference among the

18 criteria, followed by housekeeper and cook in second place, and good

looks in third place. Other criteria that might seem relevant to the

evolutionary argument (e.g., ambition and industriousness, good health)

produced considerably smaller sex differences. The appropriateness of

focusing on the criteria pertaining to earning ability and domestic skill

within the Buss et al. data is also supported by the good agreement across

the ranking and rating data sets for sex differences in the valuation of

financial provider, r (33) = .77, p < .001, and domestic skill, r (33) =

.68, p < .001(whereas the agreement in the valuation of looks was

considerably poorer, r (33) = .33, p < .10). In addition, as Buss et al.

(1990) reported, the sex difference in the preferred age of mates was fully

intact in the 37 cultures data.

Additional evidence for the social structural predictions emerged when we

evaluated the pattern of sex differences in preferences across societies.

Consistent with the division of labor principle, a substantial relation

emerged between the sex difference in valuing a spouse's domestic skills

and the sex difference in valuing a spouse's capacity to provide a good

income. Specifically, based on the ranking measure, the sex differences in

the good earning capacity criterion and the good housekeeper criterion were

correlated across the cultures, r (33) = .66, p < .001. Based on the rating

measure, the correlation between the sex differences in the financial

prospect criterion and the housekeeper-cook criterion was similar, r (35) =

.42, p < .01. These positive correlations indicate that, to the extent that

women more than men reported seeking a mate who is a good breadwinner, men

more than women reported seeking a mate who is a good homemaker. In

addition, the sex difference in the preferred age of one's spouse bore a

positive relation to the sex difference in preference for a good earner, r

(35) = .34, p < .05 for the ranking data and r (35) = .36, p < .05 for the

rating data. Similarly, the sex difference in preferred age also bore a

positive relation to the sex difference in preference for a good

housekeeper and cook, r (35) = .58, p < .001 for the ranking data and r

(35) = .60, p < .001 for the rating data. These relationships show that to

the extent that the sex difference in the preferred age of spouses was

large, women more than men preferred mates who were good providers and men

more than women preferred mates who were good domestic workers. The

division of labor provides the logic of all of these relationships: Women

who serve in the domestic role are the complement of men who serve as

breadwinners, and the pattern of older husbands and younger wives

facilitates this form of marriage.

As we noted in the prior subsection, the key social structural prediction

is that men's tendency to select wives for domestic skill and younger age

and women's tendency to select husbands for earning capacity and older age

diminish as women and men assume more similar roles in the wage economy and

the family and societies thereby attain a higher level of gender equality.

To test this hypothesis about role similarity lessening these sex

differences, we represented societies' gender equality in terms of archival

data available from the United Nations (United Nations Development

Programme, 1995). These data were available for most of the 37 cultures

studied by Buss et al. (1990). Of the many societal attributes compiled by

United Nations' researchers, the most relevant to our hypothesis is the

aggregate gender empowerment measure, which represents the extent to which

women participate equally with men in economic, political, and

decision-making roles. This index increases as (a) equality is approached

in women's percentage shares of administrative and managerial jobs and

professional and technical jobs, (b) women's percentage share of

parliamentary seats rises, and (c) women's proportional income share

approaches parity with men's. As assessed by this index, Norway has the

greatest equality, followed by Sweden, Denmark, Finland, New Zealand,

Canada, and the United States.

The gender-related development index is another useful indicator of

societal-level gender equality. It increases with a society's basic

capabilities to provide health (i.e., life expectancy), educational

attainment and literacy, and wealth, but imposes a penalty for gender

inequality in these capabilities. Whereas the gender-related development

measure reflects equality in basic access to health care, education and

knowledge, and income, the gender empowerment measure is a purer indicator

of equal participation in economic and political life. In the set of 37

cultures, the gender empowerment index and the gender-related development

index were significantly related, r (33) = .74, p < .001, and both of these

indexes were moderately correlated with general indexes of human

development and economic development. One limitation of the gender

empowerment measure and the gender-related development index is that they

are based on data from the early 1990s. Because the Buss et al. (1990) data

were collected in the mid-1980s, these indexes are from a slightly later

time period, but the relative position of the cultures should remain

approximately the same.

For the Buss et al. (1990) 37 cultures data, we calculated the

correlations of these indexes with the sex differences in valuing a mate as

a breadwinner and as a domestic worker-the two criteria most relevant to

the traditional division of labor. These correlations for the ranking and

the rating data are displayed in Table 1. The critical social structural

prediction was supported: As gender empowerment increased, the tendencies

decreased for women to place greater emphasis than men on a potential

spouse's earning capacity and for men to place greater emphasis than women

on a potential spouse's domestic skills. As expected in terms of the

gender-related development index's less direct representation of the

similarity of women's and men's roles, its correlations with these sex

differences were somewhat weaker.

As shown in Table 2, examination of the age differences preferred by men

and women in the 37 cultures showed that as gender equality increased,

women expressed less preference for older men, men expressed less

preference for younger women, and consequently the sex difference in the

preferred age of mates became smaller. These differences in age preferences

thus reflect a sex-typed division of labor, and they eroded substantially

as gender equality increased. Although the sex difference in age preference

did not completely disappear in societies with more equal gender roles, we

endorse Glenn's (1989) view that "the smaller mean size of the difference

in the samples from more developed societies suggests that it may

eventually disappear in some of them due to continued development" (p. 23).

Preference for physical attractiveness. As also shown in Table 1,

correlations between the sex difference in valuing potential mates'

physical attractiveness and the United Nations indexes of gender equality

were low and nonsignificant. Although these findings might seem to suggest

that the tendency for men to place greater value on partners' physical

attractiveness is a universal feature of mate selection, exceptions have

been reported (e.g., Walter,1997). Moreover, in traditional societies with

arranged marriages, physical attractiveness should not be very important in

mate selection because people are constrained to choose partners mainly on

the basis of factors such as tribal affiliation, family relationships,

social status, and wealth (Rosenblatt, 1974). Freedom of choice in mate

selection should increase the chances that physical attractiveness would be

relevant to mate selection. Consistent with this idea were the findings of

Rosenblatt and Cozby's (1972) cross-cultural study of 29 societies'

ethnographic records: Spouse selection for qualities such as beauty rather

than for skills, rank, alliances, and other tangible gains was positively

correlated with the freedom of choice that people had to select spouses

according to their own preferences. Because Buss's data were drawn

predominantly from cultures in which individual mate choice is likely to be

high, physical attractiveness of potential mates could play a role in mate

selection.

Although, at least in Western nations, physical attractiveness conveys

several kinds of meaning (e.g., dominance, good adjustment, intellectual

competence, and sexual warmth; Eagly, Ashmore, Makhijani, & Longo, 1991;

Feingold, 1992b), evolutionary psychologists have argued that one attribute

in particular is conveyed by women's physical attractiveness, and this is

reproductive capacity. In this view, women's attractiveness is determined

in large part by their possession of physical attributes suggestive of

youth (e.g., neonate facial features, small waist-to-hip ratios) and good

health, and these physical cues are indicators of fertility and

reproductive value (Buss, 1989; Jones, 1995; Singh, 1993). To the extent

that women's physical attractiveness, youth, and good health are indicators

of reproductive capacity within a society, then men's preference for

physically attractive partners plausibly should be linked to their preference

for young partners and their preference for healthy partners. The logic is

that the importance of these indicators of reproductive capacity is likely

to vary jointly in response to societal factors

that affect women's reproduction (e.g., the level of parasite infection,

Gangestad & Buss [1993]). However, our analyses revealed little consistency

across the 37 cultures in such preferences. Across the cultures, men's

preference for physically attractive women was uncorrelated with their

preference for youthful women or healthy women in the ranking data,

although these factors were marginally correlated in the rating data (ps <

.10).

Within-culture data have similarly revealed inconsistent relations between

perceived attractiveness of women and their judged fertility (e.g.,

Cunningham, 1986; Tassinary & Hansen, 1998). Especially interesting is

Singh's (1993) research on the attractiveness of female figures that varied

in weight and waist-to-hip ratio. In multidimensional scaling analyses of

ratings of several features that might covary with these aspects of women's

appearance, perceived fertility clustered with depictions of women of

normal weight. Ratings of health, attractiveness, and sexiness formed an

independent group of perceptions that also clustered with figures of normal

weight. Perceptions of youth were relatively separate from these other

factors and clustered with depictions of underweight women.

Although little is known about the relation between women's attractiveness

and their actual fecundity, an exceptional study by Kalick, Zebrowitz,

Langlois, and Johnson (1998) found that facial attractiveness in early

adulthood was unrelated to number of children produced or to health across

the lifespan. Although the few participants in their sample who did not

marry were less attractive than those who did marry, once the nonmarried

were excluded, physical attractiveness was unrelated to the number of

children produced by male or female participants. Kalick et al. (1998)

concluded that "any relation between attractiveness and fecundity was due

to mate-selection chances rather than biological fertility" (p. 10). Of

course, as we noted in our critique of evolutionary psychology in this

article, hypothesized evolved dispositions, such as men's preference for

physically attractive partners, are not predicted to be related to current

reproductive success. Actual fertility and judgments of reproductive

capacity in modern societies may bear little relation to the factors

indicative of reproductive status in the EEA. Therefore, it is difficult to

know what kinds of data would validate the hypothesis that men's preference

for physically attractive mates in modern societies represents an evolved

disposition that arose during prehistoric times as a solution to the

problem of identifying fertile women.

In summary, several aspects of the findings from Buss et al.'s (1990) 37

cultures study are highly compatible with the social structural origin

theory of sex differences. The idea that the division of labor is a major

determinant of the criteria that people seek in mates fits with the

observed covariation between men seeking women who are younger and have

domestic skill and women seeking men who are older and have skill as

financial providers. The lessening of all of these tendencies with

increasing gender equality is consistent with the definition of structural

gender equality in terms of more equal participation by women and men in

wage labor and domestic labor. These sex differences in mate selection

criteria and in preferred spouse age are thus by-products of a social and

family structure in which the man acts as a provider and the woman acts as

a homemaker. More ambiguous are the sex differences in the emphasis on

mates' physical attractiveness. Our findings failed to support the

evolutionary argument that men's preference for attractive women is linked

to their preference for healthy, youthful women, which in turn are cues to

women's reproductive capacity. Although we believe that the sex difference

arises from the social implications of attractiveness in the societies in

Buss's sample, convincing evidence for either an evolutionary or a social

structural interpretation has yet to be generated. However, with respect to

the other sex differences emphasized by evolutionary psychologists, their

cross-cultural patterning suggests that they arise from a particular

economic and social system.

Within-society effects of social position. As evidence that presumably

counters the social structural interpretation of sex differences in mate

selection criteria, evolutionary psychologists (e.g., Buss & Schmitt, 1993)

have sometimes cited studies that have examined the relation within a given

culture between individuals' mate preferences and their economic resources

(e.g., Buss, 1989b; Kenrick & Keefe, 1992; Townsend, 1989). In one of the

most extensive of these studies, Wiederman and Allgeier (1992) assessed

mate preferences and anticipated income of undergraduate students from a

midwestern university and of Ohio residents. Mate preference ratings from

both samples yielded the typical sex differences in ratings of good looks

and good financial prospect. The central finding was that women's

anticipated income and their valuing of potential mates as good financial

prospect were weakly related or unrelated. That women with good financial

prospects still valued financial resources in their mates was taken as

evidence that social structural variables have little impact on women's

mate choice.

Wiederman and Allgeier's (1992) findings are uninformative in relation to

the social structural argument about mate selection because, as we noted in

our description of the social structural theory, societal gender roles

coexist with specific roles. Achieving a high paying occupation does not

necessarily neutralize the impact of broader gender role expectations.

Therefore, consistent with these broader norms, even women with

higher-than-average income commonly regard themselves as secondary

wage-earners in their marriages (Ferree, 1991) and prefer to leave the

labor force entirely or to become employed part-time while raising a family

(Herzog, Bachman, & Johnston, 1983; Tittle, 1981). Despite a substantial

income, women likely anticipate being partially dependent on their

husband's income, at least during a portion of their lifespan. Furthermore,

women who themselves have higher income would tend to come from higher

socio-economic groups and would anticipate selecting mates from their own

stratum of society. Homogamous mating on the basis of education,

occupation, and economic resources is a well established phenomenon (e.g.,

Kalmijn, 1991, 1994; Mare, 1991). Therefore, women's own income typically

should be positively related to their desired mates' financial prospects

(as found by Buss, 1989b). Although we are heartened by Wiederman and

Allgeier's (1992) attempts to test social structural hypotheses, future

within-culture analyses of mate preference should assess the influences of

specific role requirements (e.g., actual or anticipated marital roles) and

more diffuse role expectations (e.g., gender roles and expectations based

on social class and education). These points are equally applicable to

other questionnaire and interview studies of the relation between income

and the qualities preferred in mates (Buss, 1989; Townsend, 1989).

Conclusion

Considered at the level of a general metatheory of sex differences, social

structural theories provide alternative explanations of the great majority

of the general predictions about sex-differentiated social behavior that

have been featured in evolutionary psychology. Because the central

tendencies of sex differences (see Eagly, 1995; Halpern, 1997; Hyde, 1996)

are readily encompassed by both of these perspectives, neither the

evolutionary metatheory nor the social structural metatheory is

convincingly substantiated by a mere noting of the differences established

in the research literature. It is far too easy to make up sensible stories

about how these differences might be a product of sex-differentiated

evolved tendencies or the differing placement of women and men in the

social structure. This overlap in general main-effect predictions calls for

more refined testing of the two theoretical perspectives, and each

perspective is associated with a number of more detailed predictions and

empirical tests.

Certainly there are many possibilities for distinguishing between the two

approaches with appropriate research designs (see Jackson, 1992).

Evolutionary psychologists have been especially resourceful in obtaining

cross-cultural data intended to support their claims of invariance across

cultures in sex-differentiated behavior. To be maximally informative about

social structural factors, cross-cultural research should be systematically

designed to represent cultures with differing forms of social organization

and levels of gender inequality (Miller-Loessi, 1995). In addition, a

variety of other research methodologies, including experimental studies and

field studies, can yield tests of predictions that emerge from evolutionary

and social structural perspectives.

Although this article contrasts social structural explanations of sex

differences with those based on evolutionary psychology, as we noted in the

introductory section, social structural analyses are generally compatible

with some evolutionary perspectives. Our argument that sex differences in

social attributes emerge from physical differences between the sexes in

conjunction with demands of the economy, features of the local environment,

and cultural beliefs is similar in spirit to dual-evolution theories that

emphasize coevolution by genetic and cultural processes (e.g., Barkow,

1989; Boyd & Richerson, 1985; Durham, 1991; see review by Janicki & Krebs,

1998). These models consider the interplay between genes, culture, and the

current environment. Although the various coevolutionary models differ in a

number of features (e.g., whether cultural change is directed to enhance

inclusive fitness), they share the assumption that culture evolves by

processes that are separate from but dependent on genetic evolution;

culture is influenced by and in turn helps to direct genetic structures.

The coevolutionary approach is consistent with the claims of some

evolutionary biologists and behavioral ecologists that behavioral

adaptations can be maintained from generation to generation through

nongenetic, presumably social mechanisms (e.g., Sork, 1997; Waage & Gowaty,

1997). Cultural change allows for the rapid spread of behavioral tendencies

within a generation and can facilitate the transmission of behaviors from

one generation to the next (Durham, 1991). Although we recognize the

importance of evolved genetic influences on the behavior of women and

men-in particular, influences stemming from men's greater size and strength

and women's reproductive activities-an implicit assumption of our approach

is that social change is not constrained to maximize individual society

members' inclusive fitness but instead is oriented to maximize the personal

benefits and minimize the personal costs of men and women in the social and

ecological settings in which they live. Although it is difficult to conduct

research that has clear implications for the multiple levels of analysis

inherent in dual inheritance models that integrate evolutionary and social

structural processes, this type of approach hold promise as a meta-theory

of psychological phenomena.

The definitive cross-cultural test of the evolutionary psychology and

social structural origin theories of sex differences may lie in the

future-that is, in the emerging post-industrial economies in which the

division between men's wage labor and women's domestic labor is breaking

down. Notable is the increase in women's paid employment, women's

increasing education, and the increase in women's access to many formerly

male-dominated occupations. Accompanying these changes is a marked

attitudinal shift toward greater endorsement of equal opportunity for women

in the workplace and role-sharing in the home (e.g., Sherman & Spence,

1997; Simon & Landis, 1989; Spence & Hahn, 1997; Twenge, 1997a).

Nonetheless, occupational sex segregation is still prevalent with women

concentrated in occupations that are thought to require feminine qualities

and men in occupations thought to require masculine qualities (e.g., Cejka

& Eagly, in press; Glick, 1991). Given that occupational segregation

currently takes this form, social structuralists would not predict that

either gender stereotypes or sex-differentiated behavior should have

already disappeared. Instead, it seems likely that, to the extent that the

traditional sexual division between wage labor and domestic labor erodes

and women and men become similarly distributed into paid occupations, men

and women will not only be perceived as similar but actually will become

more similar. In some psychological research literatures, this idea that

sex differences are disappearing is amenable to testing, at least over a

limited span of years, with meta-analytic techniques (e.g., Feingold, 1988;

Twenge, 1997b).

Regardless of the status of scientific evidence on the convergence of the

sexes, perceivers believe that men and women are becoming more similar.

These beliefs have been demonstrated by Diekman and Eagly (1998), who

showed that people believe that women and men have converged in their

personality, cognitive, and physical characteristics during the past 50

years and will continue to converge during the next 50 years. Path analyses

suggested that perceivers function like implicit role theorists by assuming

that, because the roles of women and men have become more similar, their

attributes converge. The demise of most sex differences with increasing

gender equality, a proposition that thus fits popular beliefs about the

characteristics of women and men, is a social structural prediction that

will be more adequately tested as more societies produce conditions of

equality or near-equality.

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Author Note

Alice H. Eagly, Department of Psychology; Wendy Wood, Department of

Psychology.

Thanks are extended to David Buss for making available for reanalysis data

from his 37 cultures study (Buss, 1989b; Buss et al., 1990) and to Michael

Bailey, April Bleske, Galen Bodenhausen, David Buss, Lee Cronk, Amanda

Diekman, Martie Haselton, Dan McAdams, Radmilla Prislin, Eshkol Rafaeli,

Neal Roese, and Jeffrey Simpson for comments on a draft of the article.

Also, Crystal Toures provided assistance in locating and entering relevant

data, and Heather Franzese assisted with data entry.

Correspondence concerning this article should be addressed to Alice H.

Eagly, Department of Psychology, 2029 Sheridan Road, Northwestern

University, Evanston, IL 60208, or to Wendy Wood, Department of Psychology,

Texas A&M University, College Station, TX 77843. Electronic mail may be

sent via Internet to eagly@nwu.edu or wlw@psyc.tamu.edu.

Footnotes

Table 1

Correlations of Mean Rankings and Ratings of Mate Selection Criteria With

United Nations

Indexes of Gender Equality for the 37 Cultures Sample

Ranked criteria

Rated criteria

Mate selection criterion

and raters

Gender empowerment measure

(n = 33)

Gender-related development index

(n = 34)

Gender empowerment measure

(n = 35)

Gender-related development index

(n = 36)

Good earning capacity (financial prospect)

Sex difference

Women

Men

-.43*

-.29

.24

-.33?

-.18

.26

-.31?

-.49**

-.40*

-.23

-.43**

-.37*

Good housekeeper (and cook)

Sex difference

Women

Men

-.62***

.04

-.46**

-.53***

-.02

-.42*

-.61***

.10

-.60***

-.55***

-.05

-.60***

Physically attractive (good looks)

Sex difference

Women

Men

.16

.13

.20

-.09

.32?

.28

.22

-.44**

-.33?

.23

-.27

-.12

Note. Higher values of United Nations indexes indicate greater gender

empowerment and gender-related development. Higher mean rankings and

ratings of mate selection criteria indicate greater desirability in a mate.

The attributes were described slightly differently in the ranked and rated

data; the attributes in parentheses are from the ratings. Sex differences

in mate selection criteria were calculated as female minus male rankings

for good earning capacity and male minus female rankings for good

housekeeper and physically attractive. For sex differences, a positive

correlation thus indicates an increase in the sex difference as the

relevant United Nations index increases, and a negative correlation

indicates a decrease in the sex difference. For the reports of women or

men, a positive correlation indicates an increase in the desirability of a

criterion as the relevant United Nations index increases, and a negative

correlation indicates a decrease.

? p < .10. * p < .05. ** p < .01. *** p < .001.

Table 2

Correlations of Mean Ratings of Preferred Age Difference Between Self and

Spouse

With United Nations Indexes of Gender Equality for the 37 Cultures Sample

Raters

Gender empowerment measure

(n = 35)

Gender-related development index

(n = 36)

Sex difference

Women

Men

-.73***

-.64***

.70***

-.70***

-.57***

.70***

Note. Higher values of United Nations indexes indicate greater gender

empowerment and gender-related development. Positive ages indicate

preference for older spouse, and negative age indicates preference for

younger spouse. Because the sex difference in preferred age was calculated

as female minus male preferred age, a negative correlation thus indicates a

decrease in the sex difference in preferred age as the relevant United

Nations index increases. For the ratings by women, a negative correlation

indicates a decrease in the tendency to prefer an older spouse as the

relevant United Nations index increases, whereas for the ratings by men, a

positive correlation indicates a decrease in the tendency to prefer a

younger spouse.

*** p < .001.