Disentangling the relationships between religion and fertility

In this issue of Religion, Brain & Behavior, scholars from multiple disciplines offer comments on Philip Jenkins’ Fertility and Faith (Jenkins, 2020). The debate, and Jenkins’ response to the commentaries, contribute to moving scholarship forward in an often-neglected area in the scientific study of religion. The book tackles an extensive literature, synthesizing work on several topics: drivers of secularization, drivers of fertility decline, the relationship between religion and fertility, and whether these relationships are consistent across countries and religious communities. Through this synthesis, Jenkins argues that religiosity and fertility are tightly linked, rising and falling in tandem through time and across the world.

The commentary authors highlight several questions that remain unsolved by Jenkins’ synthesis. Voas (2022), for example, notes that Jenkins does not favor one mechanism over another, suggesting that changes in both religiosity and fertility may affect change in feedback loops. Potentially, Jenkins’ non-preference for a single mechanism is because he does not employ a strong theoretical framework to explain the relationship between religiosity and fertility, as Lynch and co-authors argue (2022). This is complicated by the range of data available to study this question. Globally, analyses of religiosity and fertility have to deal with the problem of scales of analysis, balancing studies at individual-versus country-level data, as Peri-Rotem (2022) highlights. Focusing on global trends to the exclusion of individual-level data, as well as using a lens which prioritizes a Western and present-centered viewpoint, has the potential to erase local and temporal variation in the relationship between family formation and religion both in Western and global settings (Brown, 2022; Shaver et al., 2022; Walters & Sear, 2022).

Our own work employs evolutionary theory and in-depth fieldwork to investigate the dynamics between religion and fertility. In the remainder of this editorial, we describe our efforts as part of the Evolutionary Demography of Religion project, which was designed to further understand the links between religiosity, fertility, and child success. Three of the commentaries on Fertility and Faith were contributed by members of the Evolutionary Demography of Religion team, and here we give a general description of this project. In doing so, we hope to explain how the project will further advance our understanding of the complex relationship between religion and fertility.

The project’s central hypothesis is that religious systems promote collaboration between individuals, thus facilitating greater access to social support systems among more religious women and/or families (e.g., help with childcare). The support provided to religious women and families can help offset the costs of reproduction, resulting in higher fertility compared to their secular counterparts (Shaver, 2017). Moreover, differences in fertility between religious groups are expected to vary as a result of religious groups’ ability to overcome cooperative dilemmas that themselves vary across socioecological contexts. To evaluate these hypotheses, our mixed-methods project combines anthropological and demographic methods, conducting surveys and focus group discussions across five study locations: India, Bangladesh, Malawi, The Gambia, and the United States. Our research is being conducted in partnership with local institutions including the International Center for Diarrheal Disease Research, Bangladesh (icdrr,b), the Society for Health and Demographic Surveillance in India, the West Kiang HDSS based at the Medical Research Council Unit The Gambia (MRCG@LSHTM), the Malawi Epidemiological and Intervention Research Unit (MEIRU), and the Pennsylvania State University Survey Research Center (SRC).

One of the strengths of Jenkins’ work is the quantity and range of data examined. However, generalized narratives do not lend themselves to understanding the unique dynamics of religious systems in their local cultural context. The Evolutionary Demography of Religion project was explicitly designed to explore, incorporate, and collect data on local understandings of religiosity and family formation. For each study location, we began with ethnographic work including focus group discussions to better understand: how religiosity is construed, performed, and signaled locally; what values are held around family and family planning; and what types of cooperation, including childcare, is exchanged amongst individuals in the community. We used this information to adapt standard questionnaires to each context, using locally relevant questions to collect information on religiosity, several dimensions of fertility (e.g., marriage and birth histories, future fertility intentions, fertility ideals), parental and extra-parental investment in children, and collaboration between individuals. These questionnaires were administered to between 400 and 1000 women and up to 700 of their husbands in each country. We followed up these questionnaires with a second round of focus group discussions driven by research questions that were better suited to open ended discussion. These covered several topics, including the sources of information (such as religious teachings, medical advice, non-governmental organizations) individuals consider when making family-related decisions. This research design introduces important community-specific information that is lost with country-level analyses.

The approach taken by the Evolutionary Demography of Religion project addresses several other issues raised by commentators in the book symposium. The project considers multiple scales of analysis by taking a cross-cultural approach, enabling us to examine the impact of religiosity both at the individual and community level. Detailed information collected on religious behavior, cooperation, and fertility will enable us to examine the ethnographically grounded measures of religiosity that correlate with fertility and examine potential causal frameworks to link the two. The qualitative component of the project allows us to contextualize our findings and report on the importance that men and women in each study location place on religiosity when making reproductive decisions. Lastly, we have chosen to work in communities that have differing levels of religiosity, fertility, market integration (i.e. local experiences of economic development and integration into larger market systems) and religious groups with minority/majority status so that we can better understand how relationships between these indicators vary across different types of societies.

While we are now just starting analysis on our fieldwork data, we anticipate that results from this research will contribute to many aspects of the study of religiosity and fertility, especially theory building, causality, and working at multiple scales of analysis. Analyses we pursued prior to fieldwork suggest that: religiosity is associated with emotional closeness to relatives (Lynch et al., in press) and changes in sex differences in social networks (Lynch et al., in prep a); religiosity is associated with receiving more alloparental support both in the form of physical childcare (Shaver et al., 2019, 2020), and in the form of household help (Spake et al. in prep); religious minority/majority status impacts group differences in fertility (Naz et al., in prep); and education causally drives non-religiosity across nations (Shaver et al., in prep). Apart from work that explicitly concerns religiosity, other analyses from this project have examined the impact of the COVID-19 pandemic on maternal social networks (Hassan et al., in review), the impact of market integration on marriage pathways (Schaffnit et al., in review) and social networks (Lynch et al., in prep b), the conditions under which alloparental care emerges (Weitzel et al., in prep), and maternal support networks (Page et al., in press; Spake et al., 2021).

We are grateful that Jenkins has initiated a fruitful discussion of the relationship between religion and fertility and we hope that our findings will continue to advance this discussion. More information and updates about our project can be found on our website: https://www.evolutionarydemographyofreligion.org/