Are wives and daughters disadvantaged in polygynous households? A case study of the Arsi Oromo of Ethiopia

Caroline Uggla,Eshetu Gurmu,Mhairi A Gibson

doi:10.1016/j.evolhumbehav.2017.11.003

Caroline Uggla, Eshetu Gurmu + Show 1 more

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https://doi.org/10.1016/j.evolhumbehav.2017.11.003

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Abstract

Abstract Whether polygyny is harmful for women and their children is a long-standing question in anthropology. Few studies, however, have explored whether the effect of polygyny varies for women of different wife order, and whether there are different outcomes for their sons and daughters. Because males have higher reproductive variance, especially when they are allowed to take multiple wives, parents may have higher fitness returns from investing in sons over daughters in polygynous households. Moreover, previous studies have found that first wives and their children are advantaged over monogamous and second order wives (who marry into unions later). Here we test the predictions that children of first wives will have an advantage over children to monogamous or second wives, and that sex-biased investment will be strongest among first wives. Using data from the Arsi Oromo of Ethiopia (n ~6200 children) we test whether associations with mother's wife order extend beyond childhood into adulthood by examining simultaneously child survival, education and age at marriage. We find that polygynous first wives have no child survival disadvantage, first wives' sons benefit in terms of longer education and daughters have an earlier age at marriage than daughters of monogamous women. Second wives have lower child survival than monogamous women, but surviving children experience advantages in later life outcomes, particularly marriage. These findings challenge the view that polygynous women are always doing the ‘best of a bad job'. Rather, our results suggest that via their surviving sons and daughters there may be long-term benefits for some polygynous women.

Highlights

It has often been assumed that when second wives do poorly, their marital strategy is the ‘best of a bad job’ (Krebs & Davies, 1993), as the alternative strategy would be to marry a man with fewer resources monogamously, or not marry at all. We examine this view more closely by considering how polygyny is tied to both short and long-term outcomes of sons and daughters and whether such outcomes vary by mother's wife order
We address the question of whether wife order predicts offspring outcomes and whether there are sex-specific effects of polygyny and how such effects vary by wife order
While child health can be a measure of interest in and of itself, we argue that additional measures of how offspring fare in early adulthood are necessary to better understand the consequences of polygyny that natural selection acts on

Summary

Introduction

The marriage practice where men are allowed to marry multiple wives, exists in circa 80% of human societies (Murdock & White, 1969) and its consequences for women and children has been subject to much debate (Borgerhoff Mulder, 1992; Fortunato, 2015; Gibson & Mace, 2007; Hadley, 2005; Henrich, Boyd, & Richerson, 2012; Lawson et al, 2015; Sellen, 1999; Strassmann, 1997; Strassmann & Gillespie, 2002; Winking, Stieglitz, Kurten, Kaplan, & Gurven, 2013). Negative associations with child health and survival have been found in several small-scale societies (Hadley, 2005; Omariba & Boyle, 2007; Sellen, 1999; Strassmann, 1997) but few studies have considered how factors at the individual or household level may shift the costs and benefits of polygyny. This is important because results based on an overall population may obscure the true consequences of alternative marital strategies for individual women.

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