In this report in American Sociological Review, Penn State’s Scott M. Myers estimated “the magnitude of religious inheritance” using “interviews with 471 parents in 1980 and their adult offspring in 1992.” Not surprisingly, he discovered that a person’s religiosity depends on exposure to parental religiosity. But I was stunned at the archaic language, as recently as 1996:

“Parents' marital happiness, parent-child support, moderate strictness, and a working husband/nonworking wife increase the ability of parents to transmit their religious beliefs and practices.” Yikes.

Dean Hamer tackled the concept of a "God gene" in his oft-quoted “God gene” book. He’s the National Cancer Institute researcher who made headlines in 1993 with his now-debunked discovery of a “gay” gene, which I wrote about here.

In The God Gene, Hamer attributes the “predisposition of humans towards spiritual or mystic experiences” to variants of a gene, vesicular monoamine transporter 2 (VMAT2). According to Online Mendelian Inheritance in Man, the “bible” of human genetics, the gene’s “proper function is essential to the correct activity of the monoaminergic systems that have been implicated in several human neuropsychiatric disorders." "The transporter is a site of action of important drugs.”

The monoamine neurotransmitters include serotonin, dopamine, adrenaline, and noradrenaline, which have powerful effects on mood. Might variations on the monoamine theme indeed account for religious thoughts and even visions?

Hamer’s supreme being gene candidate resurfaced in 2017 in a report by Linda A. Silveira from the University of Redlands in the journal Life Sciences Education, “Experimenting with Spirituality: Analyzing the God Gene in a Nonmajors Laboratory Course.” Students looked at variants in their VMAT2 genes. She evaluated the exercise as a learning tool. And that it is, because the class disproved the hypothesis that variants of the gene have anything to do with following a religion.

In a publication of The Royal Society, University of Cambridge economist Robert Rowthorn used a model to explore the evolutionary implications of the fact that religious people “have more children on average than their secular counterparts.” This statement is unreferenced, presented as common knowledge.

Rowthorn stated his assumptions: (1) culture determines fertility, and (2) “genetic endowment” influences predisposition towards religion. “People who carry a certain ‘religiosity’ gene are more likely than average to become or remain religious,” he stated. This is a variation of the overly simplistic “a-gene-for” mindset, aka genetic determinism.

I couldn’t help but wonder, what might a religion gene actually be? A stretch of DNA that encodes a hemoglobin variant? A form of collagen? A clotting factor? A digestive enzyme? Is it Hamer’s defrocked VMAT2 variant after all?

Rowthorn’s wrote, “The paper considers the effect of religious defections and exogamy on the religious and genetic composition of society.”

I knew endogamy in genetics meant mating within a group. So I wasn’t surprised to discover that exogamy is “the social norm of marrying outside one’s social group.” In biology, exogamy means outbreeding (animals) or cross pollination (plants). Single-celled organisms like bacteria, amoebae, and certain slime molds, lacking social norms, simply grow and then split.

The economist attempted to explain the science behind his hypothesized “religiosity gene,” unwittingly touching on the concepts of natural selection and genetic linkage:

“Defections reduce the ultimate share of the population with religious allegiance and slow down the spread of the religiosity gene." However, provided the fertility differential persists and people with a religious allegiance mate mainly with people like themselves, the religiosity gene will eventually predominate despite a high rate of defection. This is an example of "cultural hitch-hiking," whereby a gene spreads because it is able to hitch a ride with a high-fitness cultural practice.

(According to Darwin, fitness has an explicit meaning: surviving long enough to reproduce.)

Math-based simulations, Rowthorn concluded, support his “theoretical arguments” about the spread of a religiosity gene.

A study published in European Neuropsychopharmacology edges into diagnostic medicine. Researchers from Germany used polygenic risk scores to show a correlation between “strong religious activity” and increased severity of schizophrenia.

“Of 271 patients (217 Christian, 9 Muslim, and 45 without religious denomination), 102 (38%) experienced religious delusions during illness episodes,” the researchers found. Just following a religion didn’t correlate with a higher likelihood of delusions, but “strong religious activity” did.

“Other factors examined—age, gender, education level, marital status, and even if a patient was in the midst of a delusion during the interview—didn't seem to matter." "And the higher the reported religiosity, the greater the risk of delusions,” the researchers concluded.

But having more predisposing genes (higher PRS) also correlated with likelihood of delusions. “Our results suggest that the occurrence of religious delusions in schizophrenia and schizoaffective disorders is associated with environmental as well as genetic influences." "But moderate religious activity seemed to have no negative effect and may even be helpful for coping with these disorders,” the researchers conclude.

A study in social psychological and personality science addressed the underpinnings of being a nonbeliever. The article opens by describing atheists as if we were space aliens.

This social science investigation discusses “theoretical frameworks of key predictors of religious disbelief.” We atheists “witness fewer credible cultural cues of religious commitment, … followed distantly by reflective cognitive style, … and less advanced mentalizing.”