Religious celibacy: Insights from marriage and inheritance

Marriage costs and inheritance patterns may help explain why religious celibacy evolved.

Study: Religious celibacy is linked to marriage and wealth transmission practices across different world religions. Image Credit: Anna Stills / Shutterstock.com

In a recent study published in the journal Nature Communications, researchers investigated the evolutionary factors associated with lifelong religious celibacy. The study included a global cross-cultural analysis of 352 societies, using Bayesian phylogenetic multilevel modeling to test whether celibacy patterns were associated with sibling competition over parental resources.

Why would celibacy persist through evolution?

Lifelong religious celibacy involves forgoing reproduction through a permanent commitment to religious or spiritual life. Evolutionary biologists and anthropologists have long viewed the practice as an evolutionary conundrum, since celibate individuals forgo direct reproduction.

Celibacy has often been explained as an evolutionary mismatch or a by-product of adaptation. More recent research has aimed to explain religious celibacy through kin selection and resource competition. One explanation draws on kin selection theory, under which parents face trade-offs when resources are finite, particularly when several offspring compete for the same resources.

Supporting this hypothesis, historical records describe how, in land-limited agrarian systems, splitting an estate among multiple sons or paying large marriage payments for several daughters could reduce the resources available to individual offspring.

Researchers have proposed that by dedicating one child to a religious institution, families could reduce competition over ancestral assets and improve the reproductive prospects of remaining siblings. Yet anthropology has lacked a broad, phylogenetically controlled empirical test of whether marriage costs and property inheritance patterns are associated with the emergence and sex distribution of religious celibates across societies.

Tracing celibacy across 352 societies

This study aimed to address this knowledge gap by evaluating 352 societies using ethnographic data from the electronic Human Relations Area Files (eHRAF) World Cultures database and variables from the D-PLACE database. Researchers identified evidence of some form of lifelong religious celibacy in 51 societies; in the remaining societies, they found no evidence of the practice.

The researchers used a Directed Acyclic Graph (DAG), a framework for mapping relationships between variables, to identify potential confounding factors in the observational data. The model evaluated three primary socio-ecological variables: 1. Marriage transactions (e.g., dowry), 2. Marital composition (polygyny, monogamy, or polyandry) and 3. Wealth inheritance patterns, including the transmission of land between generations.

Same-sex sibling competition was central to the researchers’ proposition but was not measured directly. Instead, marriage transactions, marital composition, and inheritance patterns served as proxies for competition over family resources. The DAG guided statistical adjustment, rather than establishing the proposed mechanism itself.

The analyses controlled for shared ancestry using language trees built from data from the Automated Similarity Judgment Program (ASJP). The study’s statistical models also allowed associations to vary across major religious traditions (e.g., Christianity, Hinduism) to account for differences linked to religious affiliation.

Marriage costs and inheritance reveal a pattern.

The study’s Bayesian analysis found that celibacy occurred predominantly in monogamous, rather than polygynous, societies and was also more common where land was inherited between generations. Among the factors examined, marital composition, particularly monogamy, showed the strongest association with the presence of celibacy.

When stratified by sex, the models suggested that male celibacy was more common in societies with groom-side marriage payments and patrilineal wealth inheritance. In early 20th-century Mongolia, for example, widespread bride-wealth and polygyny coincided with up to 40% of men becoming Buddhist monks.

Conversely, female celibacy tended to be more common in societies with bride-side payments (dowries), particularly in Eurasia, as well as those practicing monogamy or polyandry. Historical examples reflected these associations. In South Korea’s Chungcheong province, where large dowries and monogamy prevailed, nunneries outnumbered monasteries three to one. Among elite families in late medieval and early modern Europe, rising dowry demands and competition for noble titles coincided with high rates of female cloistering.

When stratified by religion, the study showed that Buddhist and Christian societies provided the strongest overall support for the predicted associations. Similar celibate institutions may have developed independently in response to comparable socio-ecological pressures.

Why family economics may matter for celibacy

The present study provides cross-cultural evidence linking religious celibacy with marriage practices, inheritance patterns, and competition over heritable wealth.

Rather than identifying a single cause of religious celibacy, the findings suggest that celibacy may have co-evolved with marriage practices as one of several strategies that reduced competition for limited family resources. Religious celibacy likely arose through several interacting mechanisms, with its occurrence among men and women partly reflecting which sex faced higher marriage costs.

The study has several limitations associated with its use of historical ethnographic records. Most ethnographers were men, potentially contributing to underreporting of female celibacy and marriage practices involving women, while searches relied largely on English terminology. The researchers also caution that failing to identify celibacy in an ethnographic record does not prove that the practice was absent. Coding societies in which male and female celibacy co-occurred also introduced uncertainty into the sex-specific analyses.

Overall, the findings support the hypothesis that religious celibacy may have co-evolved with marriage and inheritance practices in societies where families competed over limited resources, providing a possible evolutionary explanation for the persistence of a practice that limits direct reproduction.