Citation

Lawson DW, Alvergne A, Gibson MA. Proc. Biol. Sci. 2012; 279(1748): 4755-4764.

Affiliation

Department of Anthropology, University College London, , 14 Taviton Street, London WC1H 0BW, UK, Department of Animal and Plant Sciences, University of Sheffield, , Western Bank, Sheffield S10 2TN, UK, Department of Archaeology and Anthropology, University of Bristol, , 43 Woodland Road, Bristol BS8 1UU, UK.

Copyright

(Copyright © 2012, Royal Society of London)

DOI

10.1098/rspb.2012.1635

PMID

23034700

Abstract

Evolutionary models of human reproduction argue that variation in fertility can be understood as the local optimization of a life-history trade-off between offspring quantity and 'quality'. Child survival is a fundamental dimension of quality in these models as early-life mortality represents a crucial selective bottleneck in human evolution. This perspective is well-rehearsed, but current literature presents mixed evidence for a trade-off between fertility and child survival, and little empirical ground to evaluate how socioecological and individual characteristics influence the benefits of fertility limitation. By compiling demographic survey data, we demonstrate robust negative relationships between fertility and child survival across 27 sub-Saharan African countries. Our analyses suggest this relationship is primarily accounted for by offspring competition for parental investment, rather than by reverse causal mechanisms. We also find that the trade-off increases in magnitude as national mortality declines and maternal somatic (height) and extrasomatic (education) capital increase. This supports the idea that socioeconomic development, and associated reductions in extrinsic child mortality, favour reduced fertility by increasing the relative returns to parental investment. Observed fertility, however, falls considerably short of predicted optima for maximizing total offspring survivorship, strongly suggesting that additional unmeasured costs of reproduction ultimately constrain the evolution of human family size.

Language: en