Intergenerational effects of early adversity on survival in wild baboons

Abstract

Early life adversity can affect an individual's health, survival, and fertility for many years after the adverse experience. Whether early life adversity also imposes intergenerational effects on the exposed individual's offspring is not well understood. We fill this gap by leveraging prospective, longitudinal data on a wild, long-lived primate. We find that juveniles whose mothers experienced early life adversity exhibit high mortality before age 4, independent of the juvenile's own experience of early adversity. These juveniles often preceded their mothers in death by 1 to 2 years, indicating that high adversity females decline in their ability to raise offspring near the end of life. While we cannot exclude direct effects of a parent's environment on offspring quality (e.g., inherited epigenetic changes), our results are completely consistent with a classic parental effect, in which the environment experienced by a parent affects its future phenotype and therefore its offspring's phenotype.

Keywords: P. cynocephalus; developmental constraints; early adversity; ecology; evolutionary biology; intergenerational effects; maternal effects.

Figure 1.. Offspring survival was influenced by characteristics of their mothers’ early-life environments.

Offspring survived relatively less well during the juvenile period if (A) their mother lost her own mother during her early life and/or (B) their mother experienced a close-in-age younger sibling. An alternative visualization of the data (C) shows an equivalent pattern when mothers, rather than offspring, are treated as the unit of analysis.

Figure 2.. Effects of maternal adversity on offspring survival are explained by reduced maternal viability.

(A) Among those offspring whose mothers experienced significant early life adversity (maternal loss and/or a competing younger sibling), poor offspring survival from ages 0–2 (while the mother was still alive) was predicted by maternal death in years 2–4 after the offspring’s birth. (B) In contrast, there was no relationship between offspring survival in the first two years of life and maternal death in years 2–4 for the offspring of mothers who did not experience early life adversity.