Cultural change beyond adoption dynamics: Evolutionary approaches to the discontinuation of contraception

Abstract

Numerous evolutionary mechanisms have been proposed for the origins, spread and maintenance of low fertility. Such scholarship has focused on explaining the adoption of fertility-reducing behaviour, especially the use of contraceptive methods. However, this work has yet to engage fully with the dynamics of contraceptive behaviour at the individual level. Here we highlight the importance of considering not just adoption but also discontinuation for understanding contraceptive dynamics and their impact on fertility. We start by introducing contemporary evolutionary approaches to understanding fertility regulation behaviours, discussing the potential for integrating behavioural ecology and cultural evolution frameworks. Second, we draw on family planning studies to highlight the importance of contraceptive discontinuation owing to side-effects for understanding fertility rates and suggest evolutionary hypotheses for explaining patterns of variation in discontinuation rates. Third, we sketch a framework for considering how individual flexibility in contraceptive behaviour might impact the evolution of contraceptive strategies and the demographic transition. We argue that integrating public health and evolutionary approaches to reproductive behaviour might advance both fields by providing (a) a predictive framework for comparing the effectiveness of various public health strategies and (b) a more realistic picture of behaviour by considering contraceptive dynamics at the individual level more explicitly when modelling the cultural evolution of low fertility.

Keywords: behavioural ecology; contraceptive dynamics; contraceptive side-effects; cultural evolution; demographic transition; evolutionary public health; family planning; fertility.

Graphical abstract

Figure 1.

Contraceptive dynamics and fertility. (a) Scatterplot of total fertility rate and ever use of modern methods of contraception. (b) Violin plot of 12 month discontinuation rates by reason for all women using any modern method. Discontinuation due to side-effects is one of the top reasons for discontinuation. (c) Scatterplot of total fertility rate and 12 month discontinuation rate due to all reasons. (d) Scatterplot of total fertility rate and 12 month discontinuation rate due to side-effects. There is a strong positive correlation between total fertility rate (TFR) and (d) discontinuation due to side-effects, stronger than that between (c) TFR and both discontinuation due to all reasons and (a) contraceptive ever-use. Note that these are crude associations and additional multivariate analysis would help elucidate these effects further. Data is taken from aggregate DHS results, accessed via https://www.statcompiler.com/en/ on 21/04/20. A total of 31 low- and-middle-income countries were included in the analysis, with surveys spanning the years 1990–2015. For all countries included, only the most recent survey which had available data on all variables used was included. All data is for all (married and unmarried, results are the same for married only) women and only refers to modern methods. The R script and data are available in Online Appendix 1. R values indicate the results of Pearson's product-moment correlation tests. *** p < 0.001. ** p < 0.01.