New research suggests that the size of a country’s cosmetics industry may be directly linked to how much fathers contribute to childcare and the level of economic inequality within that society. The findings propose that in cultures where men are active parents or where the gap between the rich and poor is wide, women are more likely to invest in their appearance to compete for partners. These results were published in the journal Evolution and Human Behavior.

Charles Darwin originally proposed the theory of sexual selection to explain why males of many species possess exaggerated physical traits. He observed that peafowl are sexually dimorphic, meaning the males and females look different. The peacock displays a massive, colorful tail to attract a mate, while the peahen remains relatively plain.

This dynamic typically arises from the biological costs of reproduction. In most species, females expend more biological energy through the production of eggs, gestation, and lactation. Because their investment in each offspring is higher, females tend to be the choosier sex. Males must consequently compete with one another to be selected.

Humans, however, do not always fit neatly into this classical model. Human females often utilize conspicuous traits or cultural enhancements, such as makeup, to increase their attractiveness. Jun-Hong Kim, a researcher at the Pohang University of Science and Technology in the Republic of Korea, sought to explain this exception.

Kim aimed to determine if human mating follows a “revised” sexual selection theory. This framework suggests that the direction of mate choice depends on which partner contributes more resources to the relationship. If males provide substantial care and support, they become a limited and sought-after resource.

When men invest heavily in parenting, the cost of reproduction becomes high for them as well. The theory predicts that under these conditions, men will become more discriminating in their choice of partner. Consequently, women may compete for these high-investment males by enhancing their physical appearance.

The researcher also considered the role of economic environment. In societies with high economic inequality, a partner with resources can provide a substantial advantage in survival and reproductive success. This suggests that financial stratification might also intensify female competition for high-status mates.

To test these hypotheses, Kim conducted a cross-cultural analysis involving data from up to 55 countries. The study used the total financial size of the cosmetics industry in each nation as a proxy for female ornamentation and male choice. This data was sourced from Euromonitor, excluding baby products and men’s grooming items.

The researcher needed a way to measure how much fathers contribute to family life across different cultures. Kim utilized data from the OECD regarding the ratio of unpaid domestic work and childcare hours performed by women versus men. A lower ratio indicates that men are doing a larger share of the domestic work.

Economic inequality was measured using income inequality data from the CIA and a social mobility index from the World Economic Forum. These metrics helped determine how difficult it is to move between economic classes. The study also controlled for factors like urbanization and Gross Domestic Product per capita.

Kim’s analysis revealed a strong association between paternal effort and the beauty market. In countries where men performed a higher proportion of childcare and domestic labor, per capita spending on cosmetics was higher. This supports the idea that when men are active caregivers, they become “prizes” that warrant increased mating effort from women.

The study quantified this relationship with specific monetary figures. The data indicated that for every hour increase in paternal investment relative to maternal investment, per capita spending on cosmetics rose by roughly $2.17. This trend held true even when accounting for the general wealth of the nation.

Economic disparity also emerged as a strong predictor of beauty spending. The analysis showed that as income inequality and social mobility scores increased, so did the size of the cosmetics industry. This suggests that in stratified societies, women may invest more in their appearance to attract partners who can offer financial security.

The study posits that this behavior is a form of mutual mate choice. Unlike many mammals where one sex is clearly the chooser and the other is the competitor, humans appear to engage in a bidirectional assessment. Men evaluate potential partners based on cues of fitness and fertility, which cosmetics can highlight.

Kim also tested other variables that frequently appear in evolutionary psychology literature. One such variable was the operational sex ratio, which compares the number of marriageable men to women. Previous theories suggested that a surplus of women would lead to higher competition and beauty spending.

However, the results for sex ratio were not statistically significant in this model. The density of the population also failed to predict variations in cosmetics use. The primary drivers remained paternal investment and economic stratification.

The researcher checked for geographic clustering to ensure the results were not simply due to neighboring countries acting similarly. Visualizing the data on maps showed no distinct regional patterns that would skew the statistics. This suggests the link between parenting, economics, and cosmetics is not merely a byproduct of shared regional culture.

There are limitations to this type of cross-cultural research. The study relies on observational data, which can identify associations but cannot definitively prove causation. It is possible that other unmeasured cultural factors influence both how men parent and how women spend money.

The measurement of paternal investment was also restricted by data availability. Because the study relied on OECD time-use surveys, the analysis regarding childcare was limited to developed nations. This reduces the ability to generalize the findings to non-industrialized or developing societies.

Kim also notes that unpaid work hours are an imperfect proxy for total paternal investment. This metric does not capture the quality of care or the emotional support provided by fathers. It focuses strictly on the time spent on domestic tasks.

Future research could address these gaps by using more direct measures of parenting effort. Kim suggests that standardized surveys across a wider range of cultures could provide granular detail on how fathers contribute. This would allow for a more robust test of the revised sexual selection theory.

The study provides a new lens through which to view the multi-billion dollar beauty industry. Rather than seeing cosmetics solely as a product of modern marketing, the research frames them as tools in an ancient biological strategy. It highlights how economic structures and family dynamics shape human behavior.

This perspective challenges the stereotype that sexual selection is always male-driven. It underscores that in humans, the high cost of raising children makes distinct demands on both parents. When men step up as caregivers, the dynamics of attraction and competition appear to shift in measurable ways.

The study, “Paternal investment and economic inequality predict cross-cultural variation in male choice,” was authored by Jun-Hong Kim.