Himba women who face greater resource constraints are less discriminating in the number of partners they are open to, & have stronger preferences for resource-related traits; number of dependants was an important predictor

Resource demands reduce partner discrimination in Himba women. Sean P. Prall and Brooke A. Scelza. Evolutionary Human Sciences (2020), 2, e45, doi:10.1017/ehs.2020.43

Abstract: Where autonomy for partner choice is high, partner preferences may be shaped by both social and ecological conditions. In particular, women’s access to resources can influence both the type and number of partnerships she engages in. However, most existing data linking resources and partner choice rely on either priming effects or large demographic databases, rather than preferences for specific individuals. Here we leverage a combination of demographic data, food insecurity scores and trait and partner preference ratings to determine whether resource security modulates partner preferences among Himba pastoralists. We find that while food insecurity alone has a weak effect on women’s openness to new partners, the interaction of food insecurity and number of dependent children strongly predicts women’s openness to potential partners. Further, we show that women who have more dependants have stronger preferences for wealthy and influential men. An alternative hypothesis derived from mating-market dynamics, that female desirability affects female preferences, had no effect. Our data show that women who face greater resource constraints are less discriminating in the number of partners they are open to, and have stronger preferences for resource-related traits. These findings highlight the importance of ecological signals in explaining the plasticity of mate preferences.

Keywords: mate choice; food insecurity; transactional sex

Discussion

Male access to resources is believed to be one of the primary factors in female mate choice, and has
broad empirical support across taxa. Here, we examine how resource scarcity affects women’s openness to new partners, and how the relative importance of resource-related traits changes as resource
scarcity increases. Women with more dependants, and women with more dependants who are
more food insecure, show attenuated discrimination of potential partners, and are more likely to
give any individual male higher preference ratings. We also predicted that other resource related traits,
as rated by women in the study community, should be similarly related to female preference with
higher resource scarcity predicting greater weighting of these traits. Livestock wealth, as reported by
men, was a strong predictor of female preference. However, other male traits which may signal
resource acquisition or sharing potential, including being generous and hardworking, showed no relationship to resource need. In other words, while women with more dependants tended to prefer
wealthier men, the degree to which a man was viewed as being hardworking, generous or attractive
did not differ across women with varyng resource need.
Our data show a positive correlation between resource scarcity and the level of discrimination used
in a partner choice task. While definitively demonstrating a causal relationship between scarcity and
selectivity is not possible with these data, we did test an alternative hypothesis that this relationship
was simply the product of a relationship between resource need and position on the mating market,
Our results indicate that relative mate value, as measured by male desirability ratings of women, has no
impact on female preferences. Women who were viewed as more desirable by men were not more discriminating in their judgments. Given the large and multifaceted literature on assortative mating, this
finding warrants further study. In particular, use of women’s assessments of their own desirability
(self-perceived mate value), instead of male assessed desirability, may show stronger associations
Figure 2. Posterior predictions for interaction effect of number of dependants and status assessments on reported mate preferences. Posterior medians and 95% credible intervals for each rating category shown
with women’s mate choice. Here, we focus on the role that resource scarcity plays in determining preferences, but we recognize that this is just one of many potential pressure points that could be influencing partner choice.

The methods used in this study differ markedly from those that are currently standard in mate
choice studies within evolutionary psychology. We rely on individualized demographics and food
security ratings, rather than primes of resource scarcity. We also collected preference data for members
of the respondents’ own community, people well known to them, rather than standardized images or
priming vignettes. This more individualized approach is believed to increase ecological validity in
these sorts of tasks (Gervais, 2017). Furthermore, the study was conducted in a community where
resource scarcity is particularly salient, as chronic drought and limited access to market goods
mean that food insecurity is a common concern. This study therefore provides an important complement to previous findings, which have largely relied on samples from student populations in countries where resource scarcity is less common.

We found that number of dependants was an important predictor of partner preferences, both on
its own and in conjunction with food insecurity. In the case of shifting trait preferences, number of
dependants was a stronger predictor than food insecurity. It may be because food insecurity is chronically high in this population that food security alone does not produce enough variation to see large effects. Number of dependants represents a longer-term measure of resource stress than food security,
which has seasonal components, and which may fluctuate somewhat depending on conditions like the
number of recent funerals or ceremonies (where food is more abundant), as well as cultural practices
to cope with drought and low food availability (Bollig, 2010).
The results from this study add an interesting complement to the broader literature on transactional
sex and risky sexual behavior. Concurrent and sequential partnerships are common among Himba,
and not stigmatized in the way they are in many places. The majority of married men and women
across age groups have at least one additional partner, and these relationships are often long-lasting,
at times spanning several decades (Scelza et al., 2020b; Scelza & Prall, 2018). The transfer of resources
is commonly cited as an important component of women’s relationships with both their husbands and
their lovers. These can range from expectations about provisioning of cash or food to help with an
emergency to smaller food gifts and trinkets such as bracelets and mobile airtime. We therefore see
the relationship between resource stress and openness to romantic partners to be driven in part by
expectations that men can buffer shortfalls, in much the same way that transactional sex operates
in other sub-Saharan contexts.

Limitations

This study uses a novel trait and partner preference trait rating task, where participants rate individuals
known to them in the community. In most cases, this is preferable to using self-perceived traits, in that
it assesses community perception of individual community members, and as such should be a more
accuate representation of individual characteristics. However, this means that these results are difficult
to compare with many similar studies that use self-perceived mate value (e.g. Fisher, Cox, Bennett, &
Gavric, 2008). Additionally, trait ratings of known individuals may be subject to bias based on personal history, and traits like attractiveness are subject to non-physical influences when assessing
known individuals (Kniffin & Wilson, 2004). However, other ratings including being influential
and hardworking require knowledge of the individual in question, and the statistical methods make
idiosyncratic ratings unlikely to impact results. Complex interactions including marital status of the
rater and ratee, interpersonal dynamics and other unknown effects may be at play in the preference
ratings. Additionally, in our preference task, women were asked about how much they would like
to be in a relationship with a given set of men, but we did not specify whether this would be a marital
or non-marital relationship. Since divorce and remarriage are common, as are poygyny and concurrency, partnership status is not a disqualifer of a potential future partner, or partner interest more
broadly, but future work will seek to clarify how women best utilize different partner types.

There are other potential explanations for the relationship between resource scarcity and partner preferences that were not directly tested in this study. Some practitioners of life history theory predict that
early life stressors (including reduced access to resources) might lead to a faster life history, including
being open to a greater number of sexual partners (Simpson, Griskevicius, Kuo, Sung, & Collins, 2012).
Because of limitations in the data we had available and questions of ecological validity, we did not test
this theory here. Food insecurity in this population is largely a function of access to livestock and maize,
both of which are highly dependent on rainfall. In this drought-prone environment fluctuations in
wealth are not uncommon, so that a family with plentiful resources one year could after a multiyear
drought be suffering greatly. Given this stochasticity, as well as demographic factors like high rates
of divorce, remarriage and fosterage, which influence household composition, we do not have a simple
measure of early life stress that we could use here as a predictor. Furthermore, in our ethnographic
interviews women and men have continually stressed the importance of resource transfers as being
an important facet of both formal (marital) and informal romantic relationships. Therefore, we focused
here on how current measures of need might impact partner choice.