This is the third of four posts on religiosity and life history. The prior two are here and here.

In humans, fast life history patterns primarily involve earlier childbearing, higher completed fertility, and reduced investments in one’s own embodied capital and in each child. Slow life history patterns primarily involve later childbearing, fewer children, and higher investments. Secondarily, there are implications for sexual patterns. Obviously, the individuals having kids early are also having sex early. In addition, early childbearing tends to be associated with less stable relationships.

Another concept from evolutionary work is sociosexuality. Unrestricted sociosexuality primarily involves more comfort with and interest in casual sex and having more sex partners. Restricted sociosexuality involves a preference for committed sexual relationships and few sex partners.

It has become common to view sociosexuality as a component of fast/slow life history. For example, Del Giudice, Gangestad, and Kaplan (2016) use phrases like “fast life history traits such as … unrestricted sociosexuality.”

Nonetheless, it’s a mistake to view sociosexuality as a fast/slow life history indicator. At the group level, Schmitt (2005) found that nations with fast life history indicators (low birth weights, more child malnutrition, higher infant mortality, lower life expectancy, more teen births, and higher fertility) tend to be more sociosexually restricted, not more unrestricted.

At the individual level, fast/slow and unrestricted/restricted have some overlapping implications, but are empirically distinct. Look at the National Longitudinal Survey of Youth 1997 (NLSY97), a U.S. study that has repeatedly surveyed a sample born in the early 1980s from their teens to late 20s. There, while teen childbearing is positively correlated with having multiple sex partners as a teen, it is in fact uncorrelated with having multiple sex partners in their mid-20s. Yes, early fertility implies early sex, but it’s not indicative of a persistently unrestricted sociosexual orientation. Looking at General Social Survey (GSS) data from 1994 to 2014 (covering all age ranges in the U.S.), the correlation between number of sex partners since age 18 and number of children ever born is significantly negative—people with more kids (a core “fast” indicator) typically have fewer sex partners as adults (an assumed “slow” indicator).

For a more systematic treatment, I ran factor analyses with the GSS and NLSY97 data. I included variables such as number of children, number of sex partners, relationship status, education, and partying (going to bars in the GSS; rates of alcohol and pot usage in the NLSY97). For the NLSY97, because it’s longitudinal I was able to include separate measures for ages 16 to 19 and for ages 24 to 27.

In neither dataset do the variables meaningfully load onto a single factor. There are two major factors, the rotated factors correspond to sociosexuality on the one hand and to fast/slow life history on the other, and the factors are only minimally correlated (despite using a rotation allowing for correlated factors). In other words, the plain indications are that, at the individual level, sociosexuality and fast/slow life history are rather distinct phenomena.

In the GSS, the sociosexuality factor contrasts restricted features (few sex partners since age 18, avoiding bars, and having married and not divorced) with unrestricted features (more sex partners, going to bars, having never married, having divorced, and nonmarital cohabitation). In addition, the sociosexuality factor contains a moderate loading for number of children—having had more children is associated with restricted features. In the NLSY97, the sociosexuality factor contrasts restricted features (avoiding nonmarital sexual activity, partying less, and, in their mid-20s, higher marriage and lower cohabitation levels) with unrestricted features (nonmarital sexual activity, multiple sex partners, partying, and, in their mid-20s, low marriage rates).

For the fast/slow life history factor, in the GSS it contrasts slow features (avoiding early childbirth, having fewer children, and having more education) with fast features (early births, more children, and less education). In the NLSY97, in addition to contrasting fertility and education, the life history factor also includes teen sexual activity, teen cohabitation, and teen marriage as fast indicators.

Restricted/unrestricted sociosexuality does not align with slow/fast life history. There are fast/restricted folks, fast/unrestricted folks, slow/restricted folks, and slow/unrestricted folks—and it’s just not the case that the slow/restricted and fast/unrestricted folks meaningfully outnumber the fast/restricted and slow/unrestricted folks.

The various groupings have distinct life history patterns. In teenage years, the unrestricted folks are partying and having sex, but the fast/unrestricted are ending their school tenures and having kids while the slow/unrestricted are taking the party to college while avoiding childbearing. The slow/restricted folks are largely abstinent in their teens; later in or after college they form stable marital relationships and ultimately end up having high numbers of kids relative to their education levels. The fast/restricted folks might start sex early, but they have relatively monogamous relationships and end up with especially high completed fertility.

So, to get back on topic, what sort of people go to church the most? Is it the slows, the fasts, the restricteds, the unrestricteds? Find out tomorrow in the concluding installment.

[Update: The concluding post is here.]