Mate Choice and the Persistence of Maternal Mortality

Abstract

Maternal mortality remains one of the leading causes of death in women of reproductive age in developing countries, and a major concern in some developed countries. It is puzzling why such a condition has not been reduced in frequency, if not eliminated, in the course of evolution. Maternal mortality is a complex phenomenon caused by several physiological and physical factors. Among the physical factors, maternal mortality due to fetopelvic disproportion remains controversial. Several explanations including evolution of bipedal locomotion, rapid brain growth, and nutritional changes and life style changes in settler communities have been proposed. The influences of human reproductive biology and sexual selection have rarely been considered to explain why maternal mortality persisted through human evolution. We entertain the hypothesis that irrespective of the causes, the risks of all factors causing maternal mortality would be aggravated by disassortative mating, specifically male preference for younger females who are generally small statured and at higher risk of obstetric complications. Maternal mortality arising due to sexual selection and mate choice would have the long-term effect of driving widowers toward younger women, often resulting in "child marriage," which still remains a significant cause of maternal mortality globally. Evolutionarily, such a male driven mating system in polygamous human populations would have prolonged the persistence of maternal mortality despite selection acting against it. The effects may extend beyond maternal mortality because male-mate choice driven maternal mortality would reduce average reproductive life spans of women, thus influencing the evolution of menopause.

Global age disparity in marriage provides support for the role of mate choice in the evolution of maternal mortality and menopause

“…Unexpectedly, a weak correlation was seen between child marriage rates and MMR, contrary to other studies that found a strong association [28,29]. Regardless of all the contributing factors, the persistence of maternal mortality would likely have contributed to and hastened the evolution of menopause by lowering the overall age of fertile women beyond which infertility mutations would begin to accumulate [7,9].…”

“…Since the father's height contributes to the skeletal growth and birth weight of the newborn, increasing height disparity between parents increases the risk for maternal mortality [7,8]. Third, when maternal mortality occurs, it leaves behind a widower who is free to remarry, exacerbating its persistence because maternal mortality has a greater consequence on a female's tness than a male's since he can still have children [7]. Thus, maternal mortality should persist longer if only one sex (i.e., female) is harmed, or more negatively harmed, tness-wise [7].…”

“…Third, when maternal mortality occurs, it leaves behind a widower who is free to remarry, exacerbating its persistence because maternal mortality has a greater consequence on a female's tness than a male's since he can still have children [7]. Thus, maternal mortality should persist longer if only one sex (i.e., female) is harmed, or more negatively harmed, tness-wise [7]. Considering that humans are more known for serial monogamy and polygamy, the persistence of maternal mortality may be attributed to the mate choice theory.…”

Origin of Sex-Biased Mental Disorders: An Evolutionary Perspective

“…Males are more sensitive than females to adverse gestational conditions and the impact can last lifetime (Navara 2014) Male susceptibility to environmental stresses Males are more susceptible than females to environmental variations throughout their lives (Bale 2009; Beaudet 2017) Male brain plasticity Males are more susceptible than females to perturbation in gene expression associated with synaptic plasticity, possibly due to gene-environment interactions (Andersen and Teicher 2008;Lai et al 2013;Mottron et al 2015) Male-driven evolution of senescence Male-male competition for early gains in reproduction may accelerate the accumulation of deleterious mutations that affect senescence (Williams 1957;Kirkwood and Rose 1991) Mate choice and the evolution of menopause A male preference for younger mates would lead to the accumulation of female infertilitycausing genes and the evolution of menopause (Morton et al 2013;Takahashi et al 2017;Chan et al 2020) Male-driven persistence of maternal mortality Child marriage and repeated marriage including serial monogamy exacerbate the problem of maternal mortality making it persist longer (Jagadeeshan et al 2019…”

“…The preference for younger women means depriving older women of the opportunity to reproduce, which could have led to the accumulation of female infertility mutations giving rise to menopause (Morton et al 2013 ; Takahashi et al 2017 ; Chan et al 2020 ). A correlated negative response to this male mating behavior has been the persistence of maternal mortality due to repeated cycles of “younger mates–maternal mortality–serial monogamy–younger mate” (Jagadeeshan et al 2019 ). Male-driven mate choice through older males mating with younger females promotes longevity in both sexes, as older, long-living males contribute their genes to both their sons and daughters (Tuljapurkar et al 2007 ), thus solving one of evolutionary biology’s paradoxes, namely why women live beyond menopause (Hamilton 1966 ).…”