Figure 2: Relationship between lifespan and reproductive success.

Female baboons in Amboseli produce a single surviving offspring once every 2.13 years on average (based on the slope of the regression line), and do not exhibit extended post-reproductive lifespans. Surviving offspring are defined here as offspring who lived to at least age 1 (note that inter-birth intervals thus differ from estimates based on all offspring produced, which we used to define competing younger siblings). Among females in our data set who reached adulthood, lifespan explains 89.5% of the variance in the total number of surviving offspring (Pearson’s r=0.946, P<2.2 × 10⁻¹⁶, N=72); thus, survival is a strong predictor of lifetime reproductive success.