Mobility and Navigation among the Yucatec Maya
Mobility and Navigation among the Yucatec Maya
Sex Differences Reflect Parental Investment 0 1 2 3
Not Mating Competition 0 1 2 3
Elizabeth Cashdan 0 1 2 3
Karen L. Kramer 0 1 2 3
Helen E. Davis 0 1 2 3
Lace Padilla 0 1 2 3
Russell D. Greaves 0 1 2 3
0 Department of Psychology, University of Utah , Salt Lake City, UT , USA
1 Department of Anthropology, University of Utah , Salt Lake City, UT , USA
2 Karen L. Kramer
3 Peabody Museum of Archaeology and Ethnology, Harvard University , Cambridge, MA , USA
Sex differences in range size and navigation are widely reported, with males traveling farther than females, being less spatially anxious, and in many studies navigating more effectively. One explanation holds that these differences are the result of sexual selection, with larger ranges conferring mating benefits on males, while another explanation focuses on greater parenting costs that large ranges impose on reproductive-aged females. We evaluated these arguments with data from a community of highly monogamous Maya farmers. Maya men and women do not differ in distance traveled over the region during the mate-seeking years, suggesting that mating competition does not affect range size in this monogamous population. However, men's regional and daily travel increases after marriage, apparently in pursuit of resources that benefit families, whereas women reduce their daily travel after marriage. This suggests that parental effort is more important than mating effort in this population. Despite the relatively modest overall sex difference in mobility, Maya men were less spatially anxious than women, thought themselves to be better navigators, and pointed more accurately to distant locations. A structural equation model showed that the sex by marital status interaction had a direct effect on mobility, with a weaker indirect effect of sex on mobility mediated by navigational ability.
Navigation; Range size; Mobility; Monogamy; Parenting; Sex differences; Maya
Humans are often described as a mildly polygynous species, an apt characterization
based on cross-cultural patterns of marriage and mating, and on sexual dimorphisms in
body, behavior, and mating psychology
(Geary 2010; Low 2015; Plavcan 2000;
Kramer and Russell 2015)
. Sex differences in mobility and spatial ability also are
widespread, and it has been suggested that they, like other sexually dimorphic traits,
may have been shaped by sexual selection
(e.g., Gaulin 1992; Jones et al. 2003)
Because large ranges pose greater navigational and spatial challenges, it is plausible
that these sex differences are related. Our aim in this paper is to consider two
evolutionary arguments that have been proposed to explain these sex differences, with
a focus on mating benefits and parenting costs.
Males show an advantage in many geometric spatial abilities
(Halpern 2013; Kimura
2000; Voyer et al. 1995)
, and some recent studies have shown a sex difference in
mental rotation as early as infancy
(Moore and Johnson 2011; Quinn and Liben 2014)
Navigational tasks show a less consistent male advantage, but where a sex difference
exists it also tends to favor males (Coluccia and Louse 2004). Males also are more
likely to use geometric and global reference cues when navigating, which facilitates
long-distance travel in novel areas
(Chai and Jacobs 2009; Lawton and Kallai 2002;
Sandstrom et al. 1998; Ward et al. 1986)
. Beginning in middle childhood, boys travel
farther than girls cross-culturally
(Hart 1979; Matthews 1987; Whiting and Edwards
, and a similar pattern is widespread (although not universal) among adults in a
variety of contexts and scales of distance. Greater male travel distances have been
described for hunter-gatherer foraging ranges
(Greaves 2006; Hurtado et al. 1992;
Marlowe 2010; Tanno 1976)
, mating and exploration ranges
Hewlett 1999; Vashro and Cashdan 2015)
, and customary weekly travel among
(Ecuyer-Dab and Robert 2004a)
. Although there is considerable
cross-cultural variation arising from local environmental, economic, and social
factors, the broad patterning in these sex differences has prompted researchers to
look for evolutionary explanations.
Cross-species patterns lend support to sexual selection arguments for these sex
differences. A male advantage in spatial ability is associated with a larger range size
in several polygynous species where males gain a reproductive advantage from
patrolling multiple female territories
(Carazo et al. 2014; Gaulin and Fitzgerald 1986, 1989;
Jasarevica et al. 2012; Perdue et al. 2011)
. The importance of mating competition is
underscored by the finding that dimorphism in range size and spatial ability is found in
polygynous vole species, but not monogamous ones
(Gaulin and FitzGerald 1986,
. Humans do not find mates the way voles do, but two recent studies in
smallscale societies suggest that mating competition may underlie sexually dimorphic range
size and spatial ability in humans as well. Among Twe forager-farmers in Namibia,
spatial ability was associated with yearly visiting range size, and men with larger ranges
had more mates
(Vashro and Cashdan 2015)
. Among Tsimané farmers in Bolivia, men
traveled farther than women only during the mate-seeking years of late adolescence and
(Miner et al. 2014)
Yet humans are an extraordinarily variable species whose mating patterns vary from
extreme monogamy to extreme polygyny, and most human behavior is highly
facultative. We might therefore predict that behaviors related to mating competition, perhaps
including range size and spatial ability, would vary with the degree of male mating
competition and would be reduced in more monogamous populations. In other words,
humans should exhibit a norm of reaction in range size in response to variation in
mating competition and polygyny. Less sexually dimorphic range sizes may in turn
lead to less sexually dimorphic spatial ability since spatial ability also is shaped by
environmental and spatial experience
(Baenninger and Newcombe 1989; Uttal et al.
. We evaluate these expectations in our study of a highly monogamous traditional
farming population, the Maya. In contrast to the Tsimané and especially to the Twe,
mating competition is minimal among the Maya: everyone marries, but only once, and
extra-pair matings appear to be rare.
Another hypothesis for the sex differences in range size and spatial ability lies in the
likelihood that travel imposes greater risks and fitness costs on reproductive-aged
women than on men, owing to their greater investment in offspring
has argued that this has made women more
harmavoidant generally, and more averse to taking physical risks
(Byrnes et al. 1999)
Females also are more spatially anxious than males
(Lawton 1994; Lawton and
Kallai 2002; Schmitz 1997)
, which may reflect these costs and may mediate their
smaller ranges. Selection pressures from male mating competition and female
harmavoidance may both be important in shaping the sex differences in range size and
(Ecuyer-Dab and Robert 2004b)
Finally, subsistence patterns also have a major influence on mobility patterns, and
cross-cultural regularities in the sexual division of labor often lead to greater male
mobility, particularly with respect to the navigational and task demands of hunting and
(e.g., Eals and Silverman 1994; Greaves 2006; Hilton and Greaves 2008;
New et al. 2007; Ogilvie 2006)
. For example, hunting, particularly pursuit hunting, is
more likely than gathering to require travel over large areas and novel terrain, which
would place greater navigational demands on men. Conversely, childcare
responsibilities constrain the type of tasks that women typically do
(Brown 1970; Hurtado et al.
1985; Kramer 2009)
. Although particular task demands vary widely, the mating and
parenting concerns discussed above play a large role in shaping the broader patterns of
the sexual division of labor.
We will evaluate these arguments using data from the Maya, with a focus on
mating competition and parenting constraints. We think it likely that both have been
important in shaping the sex difference in human mobility, although the effects of
the former are likely to be more variable across cultures owing to the large variation
in human mating patterns. This speaks strongly to the Maya case: if the mating
hypothesis is as facultative as we expect, it would predict minimal sex differences in
mobility in the mating years in this highly monogamous population. We expect that
parenting constraints on women, in contrast, would be less variable across cultures,
perhaps leading to a less facultative sex difference. If so, we would expect to see
associated traits, such as spatial anxiety, found among the Maya and widely across
Our first aim is to assess whether there is a sex difference in mobility among the
Maya and whether it is consistent with the facultative mating argument discussed
above. As noted previously, mating competition is minimal among the Maya: marriage
partners are found within a close-knit community, out-of-wedlock births and divorce do
not occur, and remarriage is virtually unknown. We therefore expect that the sex
difference in range size will be comparatively small in this population during the
mate-seeking years. A sex difference in mobility resulting from parenting constraints
on women, by contrast, would be most evident at older ages when people are caring for
Our second aim is to construct an analytic model to determine how sex, navigational
ability, spatial anxiety, and mobility are related in this population. If women are less
mobile than men because of parenting constraints, it is plausible that greater spatial
anxiety, reflective of greater parenting costs, would mediate that relationship.
Navigational ability might also be expected to play a mediating role, although causation
between range size and navigational skill could go both ways: males might have better
navigational skill as an evolved consequence of selection pressures resulting from
larger ranges, while learning from environmental experience is also likely to improve
a person’s navigational proficiency.
The Yucatec Maya
To test these expectations, data on spatial ability, spatial anxiety, and mobility were
collected in a remote, rural Maya community in the interior of the Yucatan Peninsula,
Mexico. Longitudinal economic, demographic, subsistence, and social trends have
been studied in this community since the early 1990s
(Kramer 2005; Kramer and
Boone 2002; Kramer and McMillan 2006; Lee and Kramer 2002)
. Until recently, the
community had limited access to wage labor, education, medical care, market
opportunities, and goods. Although rapid economic development began to occur in the early
2000s when a paved road was built, most households today still subsist on small-scale
maize cultivation, growing most of the food they consume, and selling small quantities
of corn and honey to purchase basic household goods. Here we describe the population
at large and focus on those factors that most directly affect age and sex differences in
spatial ability, spatial anxiety, and mobility.
Factors Affecting Sex Differences in Mobility and Range Size
Maya boys and girls are given great latitude from an early age to explore their
environment independently. As soon as children are able to walk they are free to roam
and frequently are found away from their family compounds, visiting friends and
relatives or running errands. Much of a child’s day is spent outside in an unstructured
landscape where they participate in unsupervised play and subsistence activities (field
work, collecting firewood and water) and often are unaccompanied by adults. Even
though today children spend more time at school, how children grow up in terms of
spatial exploration has changed little and is similar across the age range of study
Young adults are more likely to be educated and engage in wage labor than older
adults. Between 1993 and 2013 completed education among 18–25-year-olds increased
from a mean of 4.5 years to 9.4 years. Today, most children attend the local school until
about the age of 13, with no sex difference in completed years of schooling (males
M = 9.6, SD = 2.9; females M = 9.3, SD = 2.7; t91 = 0.53, p = 0.60). During their teens,
opportunities to leave the village increase both for education and wage labor. At this
time individual differences, but not sex differences, begin to emerge in how and
where people spend their time. Since 2002 and the complete devastation of crops by
hurricane Isidora, unmarried adults more commonly work outside the community for
several years before marrying, at which time all women and most men quit their wage jobs
and return to the village. In 2014, equal numbers of males (n = 12; 10%) and
females (n = 11; 13%) ages 18–30 worked outside the community. All female wage
laborers are unmarried, whereas several male wage workers are married. Wage work can
take both males and females some distance from home, although they maintain close ties
and often return on the weekends.
In contrast to young (single) adults, married men and women differ in how and
where they allocate their time, with women typically traveling with others and men
often traveling alone. Married men spend much of their day traveling to and from
agricultural fields or into the forest to hunt and collect thatch or other forest products.
Recently, farmers have expanded into remote and previously uncultivated areas of their
territory, and into even more remote areas to establish apiaries. Consequently, men
often are alone for long hours in the forest. Although married women’s spatial lives are
more focused in the village, women travel in small parties into the forest to collect
firewood, medicinal herbs and forest fruits, or they accompany other family members
to work in the fields. Nursing women spend less time in the field than non-nursing
women, and mothers of nursing infants less than a year old do no field work
Navigation can be challenging in this environment because the densely vegetated
forest conceals landmarks, and the sun often is obscured by the vegetation and cloud
cover. The Maya do not have cell phones or GPSs and trails often are ephemeral.
During interviews, older Maya men were forthcoming in talking about their discomfort
at becoming lost, and most had been lost in the forest at some point in their adult lives.
Younger men were commonly unconcerned about losing their way, but in many cases
had never been lost. Women also report having been lost, but they rarely travel alone
and seldom are at great distances from the village. Men, women, and children are well
acquainted with other Maya communities, and from a young age they travel away from
home to visit family, market towns or health clinics, or attend fiestas and religious
In sum, although mobility for males and females at all ages has generally increased
in recent years, study participants grew up under similar conditions in terms of having
great freedom to explore their environment from an early age. Young adults, especially
females, travel more than previously and are equally engaged in wage labor and
education. However, following marriage, sex differences in mobility become
Monogamous Marriage and Low Variance in Male Quality
Marriages are stable and monogamous for life. No married adult (n = 214) living in the
village has been divorced, and divorce has never been documented in the reproductive
histories collected annually over the past 22 years. Widows and widowers are usually
well into their fifties or sixties when they lose their spouse and do not remarry, with
only one known exception. Of adults 30 and older, 86% of women (n = 80) and 95%
(n = 77) of men are married or widowed. Although interactions with outsiders have
increased, most marriage partners (92%) are from within the community, and rates of
exogamous marriage are similar for males (9.7%, n = 11) and females (10.4%, n = 11).
Maya girls are not strongly sheltered or guarded. However, in the past they had little
opportunity to pursue relationships on their own. Although travel to boarding schools
and wage labor jobs likely has increased exposure to premarital conception,
out-of-wedlock births are unknown. If a young woman conceives while single, she
quickly marries. The Maya are forthcoming and open about their relationships, and
although paternity is difficult to assess, there is little evidence of extramarital affairs, and
only one case is known out of 150 reproductive histories collected in the past 20 years.
Husbands and wives share the same house, jointly discuss many household
decisions and enjoy affable marriages and family relations. Because of the prevalence of
lifelong monogamy, male and female fertility rates are nearly identical. Of married
adults 40 and older, females have a mean completed fertility of 6.0 children (SD = 2.8,
n = 54) and men, 5.91 children (SD = 2.6, n = 58). Compared with comparable
small-scale societies, variance in male fertility is very low
The adherence to monogamy is perhaps best understood in the context of several
historic factors that contribute to low variance in male quality, and a lack of competition
for mates or access to resources. The ejido land tenure system, instituted following the
Mexican revolution, allocated to each community collectively owned land for growing
crops and hunting, pasturage, and woodland. Ejido lands cannot be bought, sold, or
inherited by individuals. This immutability, combined with constraints on transporting
crops to market, greatly limits competition for arable land or the accumulation of
property or wealth from surplus crop production. These factors minimize
socioeconomic variance and the ability of individuals to monopolize resources, and they level
opportunities for some males to be more successful in mate competition. Although the
potential for stratification is emerging for the first time (variance in the amount of land
under cultivation has significantly increased; F = 8.04, p = 0.005, Levene’s test),
differences in male quality are not yet evident. This may be because in a rapidly
changing and uncertain economic and social environment, status is difficult to
establish. For example, the market price of maize almost halved in 2014, leaving those males
who had invested in mechanized farming in large amounts of debt.
To evaluate sex differences in navigational ability, spatial anxiety, and mobility, 148
Maya adults ages 15–50 participated in the 2014 study. Interviews and testing were
conducted by Greaves and Kramer in Spanish or Maya, depending on the Spanish
fluency of the participant. Half of the village’s adult population contributed to the study
(Table 1), and testing took place in the participant’s household compound. The village
is closely nucleated, and all compounds are situated within a kilometer of each other.
Participants were asked about 20 locations in the region, and for each place they were
asked whether they had been there never, once, a few times, or many times. This forms
a 4-point ordinal scale (0–3) for each location. The average over the 20 locations is our
mobility measure for each individual. This measure incorporates both number of places
visited and frequency with which they have been visited. It is a cumulative measure of
Male (n = 70)
Female (n = 78)
Average age 26.4 (SD = 11.4) 29.5 (SD = 11.7)
% married 44% 65%
Average age at first birth 22.5 (SD = 3.2) 21.8 (SD = 4.5)
Average number of children 4.0 (SD = 2.5) 3.4 (SD = 4.5)
how far people have traveled over their lives, and it reflects mobility over a wide region
rather than daily subsistence travel. Data on daily mobility from a 2010 time allocation
study were also available for a subset of the sample.
We measured spatial anxiety with four questions designed to assess how anxious or
fearful people felt about navigating in novel areas. For example, one question was, “If
you made a wrong turn when you were out alone and did not recognize where you
were, would you be concerned that you might not find your way home?” Answers were
scored on a 3-point ordinal scale (not anxious, somewhat anxious, anxious). The
average over the four questions is our measure of spatial anxiety, with larger numbers
indicating greater anxiety.
Navigational Ability: Pointing Error
Average error in a pointing task was used as an indicator of navigational ability.
Participants were asked to point to seven locations in the region using a Brunton
Pocket Transit International Compass mounted on a tripod, with the compass sight
extended to form the pointing indicator. Correct bearings were calculated from GPS
coordinates, and the absolute value of the difference between the correct and the
pointed bearing, in degrees, is our measure of pointing error. Of the seven locations,
the two farthest were removed during analysis because of missing values and high
pointing error. Men’s and women’s error distributions for these two locations were
indistinguishable, suggesting unfamiliarity with these locations rather than a testable
difference in pointing accuracy. The five remaining locations were at an average
distance of 33.3 km (SD = 15.4 km, range 12.7–49.0 km) from the community.
Navigational Ability: Wayf inding by Self-Report
We asked participants three questions to assess their wayfinding ability, each of which
could be answered with a 3-point ordinal response. Participants were asked how readily
they could point north when they were away from camp, whether they or others usually
do the navigating when traveling with others, and whether or not they are good at giving
directions. Higher numbers indicate better wayfinding ability. These questions were
adapted from the longer Santa Barbara Sense of Direction Scale
(Hegarty et al. 2002)
which has been validated in Western populations with behavioral navigation measures.
Sex-difference analyses, multivariate structural equation modeling, and graphic
productions were performed with R (version 3.1.2) and AMOS (version 22).
Our first goal was to evaluate whether the sex differences frequently reported for other
societies are also found among the Maya.
Women reported significantly higher levels of spatial anxiety than men (t150 = −2.16,
p = 0.03) and pointed less accurately (t139 = −3.6, p < 0.001), whereas men reported
better sense of direction, t149 = 4.3, p < 0.001 (see Table 2 for means). To see whether
age moderated these relationships, we added age and age-squared (since the effect of
age is likely to be nonlinear) as predictors in separate regressions on the three
dependent variables. Sex remained a significant predictor of spatial anxiety, pointing
error, and sense of direction, whereas age had no effect.
Mobility was not significantly different when the entire sample of men and women
was considered across the lifespan (t154 = 0.70, p = 0.48). This is the case even when
we control for age and age-squared. However, marriage had a strong effect on men’s
mobility. Separate analyses for men and women show that when both age and marital
status are entered into the model, mobility is significantly greater among married men
(M = 1.17, SD = 0.45) than unmarried men (M = 0.67, SD = 0.07; t73 = −3.67,
p < 0.001), whereas marital status had no effect on the mobility of women
(t79 = −0.51, p = 0.61) (Figs. 1 and 2). Unmarried Maya men and women did not
differ in their mobility (t95 = 0.05, p = 0.96), but the sex difference becomes significant
after marriage. Married men had significantly greater mobility than married women
(t62 = −2.13, p = 0.04), which can account for the sex difference in mobility in middle
age seen in Fig. 1.
Relationship among Navigational Ability, Anxiety, and Mobility
We used structural equation modeling (SEM) to evaluate other possible indirect effects
that could help explain variation in mobility. One implication of the parenting
hypothesis is that the risks and costs of travel have selected for greater spatial anxiety in
women, and that women in consequence do not travel as far as men. We therefore
Spatial anxiety and wayfinding are ordinal scales derived from interviews; pointing error is absolute degrees of
error (out of 360) in pointing to known distant locations; mobility is an ordinal scale based on the number and
frequency of visits to 20 locations in the region. Cohen’s d is the effect size used to indicate the standardized
difference between the male and female means. **p < 0.001, *p < 0.05 (t-test)
considered spatial anxiety as a possible mediator between sex and mobility. If larger
ranges are a selection pressure favoring better navigational ability, then navigational
ability is also a possible mediator between sex and mobility. We have two variables that
measure navigational performance: pointing error (a behavioral measure) and the
wayfinding questions (a self-report measure). We used these two variables to construct
the latent variable “navigational ability.” For the SEM analysis, we reversed the
directionality of pointing error, calling it “pointing accuracy,” so that all the
navigational measures are in the same direction (higher scores meaning better navigation).
Because mobility increased after marriage with men but not with women, we included
an interaction term of sex by marital status. Since mobility is a cumulative measure, we
also controlled for age and used the residual of mobility by age in the model.1
We initially ran a model that included all these variables as predictors of mobility. It
included direct effects on mobility of marital status and of the sex-by-marital-status
interaction, and indirect effects of sex on mobility, mediated by spatial anxiety and
navigational performance. This model is similar to that shown in Fig. 3, but with a
direct path from spatial anxiety to mobility. Multivariate analysis by structural equation
modeling (SEM) was conducted using maximum likelihood estimation. To account for
missing data points, full information maximum likelihood (IML) measures used all
available data in order to generate maximum-likelihood-based statistics.
Goodness-of-fit was assessed for the overall model, and although the fit measures
approached acceptable levels, the effect of spatial anxiety on mobility was not significant.
We therefore tried a second model, as shown in Fig. 3, with spatial anxiety affecting
mobility through navigational ability. Standard goodness-of-fit measures for this model
are acceptable (χ2 = 14.36, RMSEA 0.038, CFI 0.996). RMSEA (root mean square
error of approximation) values less than 0.08 and CFI (comparative fit index) values
more than 0.9 indicate that the model adequately represents the data
and Cudeck 1993)
This model, shown in Fig. 3, indicates that marriage and the interaction effect of
marriage by sex both had direct positive effects on mobility (β = 1.12, p = 0.003 and
β = 0.93, p = 0.017, respectively), supporting earlier analyses showing that married
individuals were more mobile and that married men had greater mobility than married
women, unmarried men, and unmarried women. Sex had an indirect effect, with men
having better navigational performance, and better navigational performance in turn
predicting greater mobility. Women also reported greater spatial anxiety. The indirect
effect of spatial anxiety on mobility was in the expected direction but did not reach
statistical significance; however, its inclusion did make the model perform better
Marital Status and Sex
Given these results, we wanted to know why marriage had a positive effect on mobility
for men. The result was not anticipated, and a similar effect was not found for women.
We therefore categorized the 20 locations used to calculate mobility by the primary
reason for visiting each location. Destinations were divided into four categories:
locations to visit kin, locations to procure resources, wage labor locations, and other
(hospital or religious trips). Married men were significantly more likely than unmarried
1 Weighted effect codes were applied to the variables “sex” and “marital status” in the SEM
(Cohen et al.
. With weighted effects coding, males were coded as 1 and females as −0.93, where 0.93 is the ratio of
females to males in the sample. Similarly, married individuals were coded as 1 and unmarried persons as
−0.86, where 0.86 is the ratio of unmarried to married individuals in the sample.
men to visit locations to procure resources (t78 = −3.21, p = 0.002) and to engage in
wage labor (t66 = −2.92, p = 0.005).
In order to see whether daily travel showed the same effect as regional mobility, we
analyzed time allocation data collected in 2010. The data are for a subset of the sample
so could not be included in the path model. Scan samples (n = 5419) were collected on
male (n = 15) and female (n = 23) adults ages 15–50, and daylight observations were
aggregated by location to indicate the proportion of time an individual spent in or out of
the village (Fig. 4). Time out of the village includes time spent in the fields and forest,
as well as in other more distant communities. Before marriage, there was no difference
between the proportion of time spent in the village by men (M = 0.66, SD = 0.28) and
women (M = 0.67, SD = 0.31, t11 = −0.05, p = 0.96). After marriage, however, the
proportion of time spent in the village decreases for men (M = 0.39, SD = 0.16) and
increases for women (M = 0.92, SD = 0.17) such that married men spend more than
twice as much time as married women out of the village (t21 = −7.66, p < 0.001; Fig. 4).
The change with marital status is significant for both women (t44 = 3.40, p = 0.002) and
men (t28 = 3.24, p = 0.003).
Sex Differences in Spatial Ability and Range Size
Maya men on average performed better than women at our navigational tasks. They
pointed more accurately to known but distant locations and had a better self-reported
sense of direction. Women also reported more anxiety about getting lost and finding
their way in unfamiliar locations.
It would be reasonable to expect these indicators of navigational ability and
confidence to reflect larger male range sizes, but the result here is not straightforward. Men
and women overall did not differ significantly in our primary measure of mobility,
which was designed to capture mobility over the wider region. However, men do travel
significantly farther after marriage whereas women do not. Path model results show
that this interaction between sex and marital status had a direct effect on mobility. A
smaller effect of sex on mobility was indirect, mediated by men’s better navigational
The sex differences in navigational performance and spatial anxiety despite similar
mobility is interesting. One interpretation could be simply that these sex differences are
not locally calibrated to differential ranging experience. This could be the case with
respect to spatial anxiety; a less facultative response would make sense to the extent
that spatial anxiety reflects women’s greater harm-avoidance generally, in response to
women’s universally greater parental investment
The sex difference we found in navigation performance despite similar mobility is
more likely to reflect limitations in our mobility measures. Larger ranges, other things
being equal, pose more navigational challenges, but other factors are probably also at
play in shaping sex differences in navigational experience, including the ways in which
women and men travel. Unlike Maya men, Maya women do not drive or ride bicycles,
and when they use motorized transport they do so as passengers, traveling with others.
Because their experience as active navigators is limited to distances traveled on foot,
they have less regional navigational experience despite their having traveled (as
passengers) widely over the region, visiting many of the same places as men. They
are also more likely to travel with others, even when traveling on foot. A similar
argument was made to explain the sex difference in some spatial measures among
Hadza foragers. As is common among foragers, Hadza women forage in groups
whereas men hunt alone, which means that men are more dependent on their own
sense of direction
(Cashdan et al. 2012)
. A similar pattern is described for the Twe
(Vashro et al. 2015)
. These factors may have played a role in shaping sex differences in
navigational ability, over and above sex differences in range size.
Reasons for Sex Differences in Range Size
One hypothesis for the sex difference in range size, particularly in “visiting” or “exploration”
ranges (i.e., to other camps, villages or towns), is that men gain fitness benefits through
increased mating opportunities. This scale of mobility has not received much attention from
anthropologists, but two recent studies of polygynous forager-farmer groups, the Twe and
Tsimané, found evidence linking larger male visiting ranges to mating competition, in
support of this hypothesis
(Miner et al. 2014; Vashro and Cashdan 2015)
Our mobility measure was also designed to capture mobility on this scale.
However, we anticipated that the sex differences in range size would be low and
not associated with mating competition in this population because the Maya are
highly monogamous, as reflected both in their marital behavior (see ethnographic
background section) and in their fertility. Variance in reproductive success (RSvar)
among Maya males is lower than in other small-scale populations, including both
foragers and farmers
, and is about the same for men (6.8) and women
(7.8). This makes the Maya an interesting contrast to the more polygynous Twe
(male RSvar = 19.7; Vashro, personal communication) and Tsimané
RSvar = 19.9; von Rueden et al. 2011)
, where male mating competition appears to
be one factor driving larger male visiting ranges. Although unusual for farming
populations, the low Maya RSvar is consistent with the low variance in male
socioeconomic success described earlier, and with the apparent absence of
behaviors associated with male mating competition. It is also consistent with our finding
that there is no sex difference in range size among unmarried Maya adults.
We expected that any sex difference in regional range size among the Maya would be
associated with parenting costs rather than mating competition, and that it would result from
reduced mobility among women owing to the greater fitness costs they incur from travel. In
addition to the direct constraints of childcare on mobility, this expectation is due to the fact
that the risks of being hurt or lost while traveling exact a larger fitness cost on women since
young children are less likely to survive a mother’s death or injury than a father’s. This
would be a special case of the general evolutionary argument for women’s lower fear
threshold and aversion to taking physical risks
The mobility data, however, indicate that on a regional level, married men are
traveling more, not that married women are traveling less. Marriage and parenting
responsibilities are closely linked among the Maya since they neither divorce nor have
children out of wedlock. A post-hoc analysis of travel destinations indicates that
married men increase travel to market towns, where they can sell and exchange
agricultural products, and to administrative towns, which are centers for wage work.
Although we cannot know for certain, our inference is that because mobility changes
with marital status, married men increase their range size and seek these destinations for
work and subsistence reasons, which provides support for their families. More direct
evidence about the motive for long-distance travel is clearly needed.
Because the mobility measure is cumulative, it is limited in terms of what it can tell
us about current mobility constraints and motives. It also measures only long-distance
travel to other villages and towns, not daily or local travel to fields and forest. In order
to capture sex differences in daily mobility, we used scan sample data collected for a
subset of this sample in 2010. As with our primary mobility measure, unmarried men
and women do not differ in the proportion of time they spend away from the village.
After marriage, however, married men are spending significantly more time out of the
village, and married women significantly less.
Taken together, these data support the argument that in this highly monogamous
population, parenting, rather than mating competition, leads to a modest sex difference
in mobility during the childbearing years, and that it results from both constraints on
mobility by married women and subsistence-related travel by married men. This result
is consistent with the fact that male and female reproductive interests are closely
aligned in this monogamous population, and it serves as a useful counterpoint to the
regional mobility patterns described for more polygynous societies.
Acknowledgments Much appreciation to the Maya for their patience and ease in participating in this study
and to the members of the Spatial Cognition and Navigation (SCAN) group at the University of Utah for their
help in preparing materials and discussing results. Spatial research in the Maya community of Xculoc was
supported by NSF 0964031 (Kramer PI) and NSF IBSS 1329091 (Cashdan PI).
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International
License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a
link to the Creative Commons license, and indicate if changes were made.
Elizabeth Cashdan is a professor of anthropology at the University of Utah. She is currently PI on the
interdisciplinary Spatial Cognition and Navigation (SCAN) project, which aims to understand how
navigational demands affect spatial cognition, and how these differ for men and women through the lifespan and
Karen L. Kramer is a behavioral ecologist with research interests in cooperative breeding, and the evolution
of childhood, parenting and family formation. She has worked with the Pumé, a group of South American
hunter-gatherers, and the Yucatec Maya for the past 20 years.
Helen E. Davis is a postdoctoral fellow at the University of Utah. Her current research focuses on the impact
of formal education on individual outcomes in transitioning populations. In particular, she has examined the
factors contributing to cognitive performance, educational attainment, and the emergence of economic
inequality among the Tsimané, forager-horticulturalists.
Lace Padilla is a PhD student at the University of Utah in the Cognitive Neural Science Department. Padilla is
a member of the Visual Perception Spatial Cognition Research Group directed by Sarah Creem-Regehr,
Jeanine Stefanucci, and William Thompson. Her work focuses on individual differences in visual perception.
In 2014, she was awarded the Martin Harris Hiatt Memorial Graduate Fellowship for Underrepresented
Populations and the Clayton Fellowship for Excellence in Research with Underrepresented Populations.
Russell D. Greaves is a research associate with the Peabody Museum of Archaeology and Ethnology and an
adjunct associate professor in the Department of Anthropology at the University of Utah. He is an
ethnoarchaeologist who has studied subsistence adaptations and technology among savanna
huntergatherers in Venezuela and is interested in comparative research with small-scale agricultural societies.
Baenninger , M. , & Newcombe , N. ( 1989 ). The role of experience in spatial test performance: a meta-analysis . Sex Roles , 20 ( 5-6 ), 327 - 344 .
Betzig , L. ( 2012 ). Means, variances, and ranges in reproductive success: comparative evidence . Evolution and Human Behavior , 33 ( 4 ), 309 - 317 .
Brown , J. K. ( 1970 ). A note on the division of labor by sex . American Anthropologist , 72 ( 5 ), 1073 - 1078 .
Browne , M. W. , & Cudeck , R. ( 1993 ). Alternative ways of assessing model fit . In K. A. Bollen , & J. S . Long (Eds.), Testing structural equation models (pp. 136 - 162 ). Beverly Hills: Sage.
Byrnes , J. P. , Miller , D. C. , & Schafer , W. D. ( 1999 ). Gender differences in risk taking: a meta-analysis . Psychological Bulletin , 125 ( 3 ), 367 - 383 .
Campbell , A. ( 1999 ). Staying alive: evolution, culture, and women's intrasexual aggression . Behavioral and Brain Sciences , 22 ( 02 ), 203 - 214 .
Carazo , P. , Noble , D. , Chandrasoma , D. , & Whiting , M. ( 2014 ). Sex and boldness explain individual differences in spatial learning in a lizard . Proceedings of the Royal Society B , 281 ( 1782 ), 20133275 .
Cashdan , E. , Marlowe , F. W. , Crittenden , A. , Porter , C. , & Wood , B. M. ( 2012 ). Sex differences in spatial cognition among Hadza foragers . Evolution and Human Behavior , 33 ( 4 ), 274 - 284 .
Chai , X. J. , & Jacobs , L. F. ( 2009 ). Sex differences in directional cue use in a virtual landscape . Behavioral Neuroscience , 123 ( 2 ), 276 - 283 .
Cohen , J. , Cohen, P. , West , S. G. , & Aiken , L. S. ( 2003 ). Applied multiple regression-correlation analysis for the behavioral sciences . New York: Routledge.
Coluccia , E. , & Louse , G. ( 2004 ). Gender differences in spatial orientation: a review . Journal of Environmental Psychology , 24 ( 3 ), 329 - 340 .
Eals , M. , & Silverman , I. ( 1994 ). The hunter-gatherer theory of spatial sex differences: proximate factors mediating the female advantage in recall of object arrays . Ethology and Sociobiology , 15 ( 2 ), 95 - 105 .
Ecuyer-Dab , I. , & Robert , M. ( 2004a ). Spatial ability and home-range size: examining the relationship in Western men and women (Homo sapiens) . Journal of Comparative Psychology , 18 ( 2 ), 217 - 231 .
Ecuyer-Dab , I. , & Robert , M. ( 2004b ). Have sex differences in spatial ability evolved from male competition for mating and female concern for survival? Cognition , 91 ( 3 ), 221 - 257 .
Gaulin , S. J. C. ( 1992 ). Evolution of sex difference in spatial ability . American Journal of Physical Anthropology , 35 , 125 - 151 .
Gaulin , S. , & FitzGerald , R. ( 1986 ). Sex differences in spatial ability: an evolutionary hypothesis and test . American Naturalist , 127 ( 1 ), 74 - 88 .
Gaulin , S. , & Fitzgerald , R. ( 1989 ). Sexual selection for spatial-learning ability . Animal Behaviour , 37 ( 2 ), 322 - 331 .
Geary , D. C. ( 2010 ). Male, female: The evolution of human sex differences . Washington, DC: American Psychological Association.
Greaves , R. D. ( 2006 ). Forager landscape use and residential organization . In F. Sellet, R. D. Greaves , & P. L. Yu (Eds.), Archaeology and ethnoarchaeology of mobility (pp. 127 - 152 ). Gainesville: University Press of Florida.
Halpern , D. ( 2013 ). Sex differences in cognitive abilities . New York: Psychology Press.
Hart , R. ( 1979 ). Children's experience of place . New York: Wiley.
Hegarty , M. , Richardson , A. E. , Montello , D. R. , Lovelace , K. , & Subbiah , I. ( 2002 ). Development of a selfreport measure of environmental spatial ability . Intelligence , 30 ( 5 ), 425 - 447 .
Hilton , C. E. , & Greaves , R. D. ( 2008 ). Seasonality and sex differences in travel distance and resource transport in Venezuelan foragers . Current Anthropology , 49 ( 1 ), 144 - 153 .
Hurtado , A. M. , Hawkes , K. , Hill , K. , & Kaplan , H. ( 1985 ). Female subsistence strategies among Ache hunter-gatherers of eastern Paraguay . Human Ecology , 13 ( 1 ), 1 - 28 .
Hurtado , A. M. , Hawkes , K. , Hill , K. , & Kaplan , H. ( 1992 ). Trade-offs between female food acquisition and child care among Hiwi and Ache foragers . Human Nature , 3 ( 3 ), 1 - 28 .
Jasarevica , E. , Williams , S. , Roberts , M. , Geary , D. , & Rosenfeld , C. ( 2012 ). Spatial navigation strategies in Peromyscus: a comparative study . Animal Behaviour , 84 ( 5 ), 1141 - 1149 .
Jones , C. M. , Braithwaite , V. A. , & Healy , S. D. ( 2003 ). The evolution of sex differences in spatial ability . Behavioral Neuroscience , 117 ( 3 ), 403 - 411 .
Kimura , D. ( 2000 ). Sex and cognition . Cambridge: MIT Press.
Kramer , K. L. ( 2005 ). Maya children: Helpers at the farm . Cambridge: Harvard University Press.
Kramer , K. L. ( 2009 ). Does it take a family to raise a child? In G . Bentley, & R. Mace (Eds.), Substitute parents: Biological and social perspectives on alloparenting in human societies (pp . 77 - 99 ). New York: Berghahn Books.
Kramer , K. L. , & Boone , J. L. ( 2002 ). Why intensive agriculturalists have higher fertility: a household labor budget approach to subsistence intensification and fertility rates . Current Anthropology , 43 ( 3 ), 511 - 517 .
Kramer , K. L. , & McMillan , G. P. ( 2006 ). The effect of labor saving technology on longitudinal fertility changes . Current Anthropology , 47 ( 1 ), 165 - 172 .
Kramer , K. L. , & Russell , A. F. ( 2015 ). Was monogamy a key step on the hominin road? Reevaluation of the monogamy hypothesis . Evolutionary Anthropology , 24 , 73 - 83 .
Lawton , C. ( 1994 ). Gender differences in wayfinding strategies: relationship to spatial ability and spatial anxiety . Sex Roles , 30 ( 11 ), 765 - 779 .
Lawton , C. , & Kallai , J. ( 2002 ). Gender differences in wayfinding strategies and anxiety about wayfinding: a cross-cultural comparison . Sex Roles , 47 ( 9 ), 389 - 401 .
Lee , R. D. , & Kramer , K. L. ( 2002 ). Children's economic roles in the Maya family life cycle: Cain, Caldwell and Chayanov revisited . Population and Development Review , 28 ( 3 ), 475 - 499 .
Low , B. S. ( 2015 ). Why sex matters: A Darwinian look at human behavior . Princeton: Princeton University Press.
MacDonald , D. , & Hewlett , B. ( 1999 ). Reproductive interests and forager mobility . Current Anthropology , 40 ( 4 ), 501 - 524 .
Marlowe , F. ( 2010 ). The Hadza: Hunter-gatherers of Tanzania . Berkeley: University of California Press.
Matthews , M. H. ( 1987 ). Gender, home range and environmental cognition . Transactions of the Institute of British Geographers , 12 ( 1 ), 43 - 56 .
Miner , E. J. , Gurven , M. , Kaplan , H. , & Gaulin , S. J. C. ( 2014 ). Sex difference in travel is concentrated in adolescence and tracks reproductive interests . Proceedings of the Royal Society of London B , 281 , 20141476. doi: 10 .1098/rspb. 2014 . 1476 .
Moore , D. S. , & Johnson , S. P. ( 2011 ). Mental rotation of dynamic, three-dimensional stimuli by 3-month-old infants . Infancy , 16 ( 4 ), 435 - 445 .
New , J. , Krasnow , M. M. , Truxaw , D. , & Gaulin , S. J. C. ( 2007 ). Spatial adaptations for plant foraging: women excel and calories count . Proceedings of the Royal Society of London B , 274 ( 1626 ), 2679 - 2684 .
Ogilvie , M. D. ( 2006 ). Changing mobility roles at the advent of agriculture: A biobehavioral reconstruction . In F. Sellet, R. Greaves , & P. L. Yu (Eds.), Archaeology and ethnoarchaeology of mobility (pp. 155 - 183 ). Gainesville: University Press of Florida.
Perdue , B. , Snyder , R. , Zhihe , Z. , Marr , M. J. , & Maple , T. ( 2011 ). Sex differences in spatial ability: a test of the range size hypothesis in the order carnivora . Biology Letters , 7 ( 3 ), 380 - 383 .
Plavcan , J. M. ( 2000 ). Inferring social behavior from sexual dimorphism in the fossil record . Journal of Human Evolution , 39 , 327 - 344 .
Quinn , P. C. , & Liben , L. S. ( 2014 ). A sex difference in mental rotation in infants: convergent evidence . Infancy , 19 ( 1 ), 103 - 116 .
Sandstrom , N. J. , Kaufman, J., & Huettel , S. A. ( 1998 ). Males and females use different distal cues in a virtual environment navigation task . Cognitive Brain Research , 6 ( 4 ), 351 - 360 .
Schmitz , S. ( 1997 ). Gender-related strategies in environmental development: effects of anxiety on wayfinding in and representation of a three-dimensional maze . Journal of Environmental Psychology , 17 ( 3 ), 215 - 228 .
Sherry , D. , & Hampson , E. ( 1997 ). Evolution and the hormonal control of sexually- dimorphic spatial abilities in humans . Trends in Cognitive Sciences , 1 ( 2 ), 50 - 56 .
Tanno , T. ( 1976 ). The Mbuti net-hunters in the Ituri Forest, eastern Zaire: their hunting activities and band composition . Kyoto University African Studies, 10 , 101 - 135 .
Uttal , D. H. , Meadow , N. G. , Tipton , E. , Hand , L. , Alden , A. R. , Warren , C. , & Newcombe , N. S. ( 2013 ). The malleability of spatial skills: a meta-analysis of training studies . Psychological Bulletin , 139 ( 2 ), 352 - 402 .
Vashro , L. , & Cashdan , E. ( 2015 ). Spatial cognition, mobility, and reproductive success in northwestern Namibia . Evolution and Human Behavior , 36 ( 2 ), 123 - 129 .
Vashro , L. , Padilla , L. , & Cashdan , L. ( 2015 ). Sex differences in mobility and spatial cognition: a test of the fertility and parental care hypothesis in northwestern Namibia . Human Nature , 27 ( 1 ). doi:10.1007/ s12110-015-9247-2.
Von Rueden , C. , Gurven , M. , & Kaplan , H. ( 2011 ). Why do men seek status? Fitness payoffs to dominance and prestige . Proceedings of the Royal Society B , 278 , 2223 - 2232 .
Voyer , D. , Voyer , S. , & Bryden , M. P. ( 1995 ). Magnitude of sex differences in spatial abilities: a meta-analysis and consideration of critical variables . Psychological Bulletin , 117 ( 2 ), 250 - 270 .
Ward , S. L. , Newcombe , N. , & Overton , W. F. ( 1986 ). Turn left at the church, or three miles north: a study of direction giving and sex differences . Environment and Behavior , 18 ( 2 ), 192 - 213 .
Whiting , B. B. , & Edwards , C. P. ( 1992 ). Children of different worlds: The formation of social behavior . Cambridge: Harvard University Press.