What do we know about the ecology of pairbond stability?

What features of the environments that people live in, whether in small-scale foraging societies like the !Kung or in industrialized societies like my own, lead to changes in the stability of marriage?

Late in 2015, I was asked to provide a brief review of science’s progress toward answering that question. I was invited to contribute a chapter on the “Ecology of Pairbond Stability” to the upcoming Encyclopedia of Evolutionary Psychological Science edited by Shackelford and Weekes-Shackelford and due to be published in print in 2018.

Update (13 Nov 16):

My chapter has been accepted and is now published! The published version is behind a paywall. Springer allows some degree of open access, though, by permitting me to make the accepted mansuscript available on my website.

• Kushnick G, 2016. Ecology of pairbond stability. In Shackelford T & Weekes-Shackelford V (eds.), Encyclopedia of Evolutionary Psychological Science (pp.1-7). NY: Springer, doi: 10.1007/978-3-319-16999-6_111-1.

While certainly related to my previous research, I had not done any work on that specific topic and so I saw the invitation as an opportunity to learn something new and to practice up on writing review articles (a type of paper that I, shamefully, have not yet published).

Here is one of the illustrations from the chapter showing the curvilinear relationship between pairbond stability and one aspect of social ecology, the relative percentage of subsistence work done by men and women.

Schematic illustration of Quinlan & Quinlan’s (2007) finding that pairbond stability was closely associated with subsistence complementarity (from Kushnick 2016).

I had a blast researching and writing the article. And it is now accepted for inclusion in the Encyclopedia (and now published as well — see the update at the beginning of the article).

In a nutshell, it expounds a fleshed out version of the following premises:

1. Evolutionary theory predicts that pairbonds should remain stable unless one or both of the partners can increase their fitness by leaving that pairbond.
2. Environmental factors, both physical (e.g., extrinsic mortality risk) and social (e.g., operational sex ratio) should shape the fitness costs and benefits of staying in the pairbond versus seeking greener pastures.
3. Most work to date on the ecology of human pairbond stability has been informed by mate desertion theory, which originates with the innovative game theory models of John Maynard Smith in the early 1980s.
4. More work is needed to develop theory that goes beyond this shortcoming.

REFERENCES:

Kushnick G (2016). Ecology of pairbond stability. In Shackelford T & Weekes-Shackelford V (eds.), Encyclopedia of Evolutionary Psychological Science (pp.1-7). NY: Springer, doi: 10.1007/978-3-319-16999-6_111-1.

Quinlan, R. J., & Quinlan, M. B. (2007). Evolutionary ecology of human pair-bonds: Cross-cultural tests of alternative hypotheses. Cross-Cultural Research, 41(2), 149-169.