The temporary cost of dominance

Abstract

In a population of wild baboons, a new way to assess biological age reveals a surprising effect of social hierarchy.

Keywords: P. cynocephalus; aging; biological age; epigenetic clock; evolutionary biology; genetics; genomics; methylation.

Figure 1.. Change in social status alters the relationship between biological and chronological aging in wild baboons.

Chronological age (how many years an individual has been alive for) can differ from epigenetic (that is, biological) age. The dotted diagonal line shows the rate where both measures match; individuals above this line are biologically older than their actual age, and individuals below are biologically younger than their chronological age. Male baboons who are socially dominant (upright, walking figure) tended to be epigenetically ‘older’ than expected given their chronological age. This relationship was reversed for male individuals of lesser ranks (sitting figure). However, changes in social status between two time points (gray arrows) alter the speed of the epigenetic clock. Low status males (male B, in blue) which gained dominance tended to become epigenetically ‘older’ relative to chronological age. In contrast, when a dominant male (male A, in red) lost status, his epigenetic age tended to decline. These findings suggest that the epigenetic clock accelerates as baboons gain social dominance, but that these aspects of biological aging are transient. This could mean that this epigenetic measure might not be associated with mortality or lifespan, as it is found for other species.