Faculty Collaboration Database

Measuring selective constraint on fertility in human life histories. Proc Natl Acad Sci U S A 2015 Jul 21;112(29):8982-6

Date

07/08/2015

Pubmed ID

26150499

Pubmed Central ID

PMC4517261

DOI

10.1073/pnas.1422037112

Scopus ID

2-s2.0-84937501622 (requires institutional sign-in at Scopus site)   13 Citations

Abstract

Human life histories combine late age at first reproduction, long reproductive span, relatively high fertility, and substantial postreproductive survival. However, even among the most fecund populations, human fertility falls far below its theoretical maximum. The extent of parental care required for successful offspring recruitment and widespread fertility decline under proper economic conditions suggest that selection on fertility is constrained by trade-offs with recruitment. Here we measure the trade-offs between life history traits under selection by approximating the slope of the selective constraint curve on two traits at the observed values. Using a selection of populations that span human demographic space, we find that the substitution elasticity of fertility for infant survival shows age-related patterns, with minimum substitution elasticities ranging from 14 to 22 for the four populations. The age of this minimum occurs earlier in the high-mortality populations relative to generation time than it does in the low-mortality populations. The human curves are qualitatively similar to one of two comparable nonhuman primate age-specific substitution elasticity curves. The curve for rhesus macaques has a similar shape but is shifted down, meaning that the threshold for switching from investing in survival to fertility is lower at all ages. The magnitude of the substitution elasticities is similar between chimpanzees and humans but the shape is quite different, rising more slowly for a longer fraction of the chimpanzee life cycle. The steeply rising substitution elasticities with age in humans has clear implications for the evolution of reproductive senescence.

Author List

Jones JH, Tuljapurkar S

Author

Test W. User test user title in the Anesthesiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Demography
Fertility
Humans
Infant
Infant Mortality
Life Cycle Stages
Models, Biological
Survival Analysis