Sex differences in adult mortality rate mediated by early-life environmental conditions

Variation in sex differences is affected by both genetic and environmental variation, with rapid
change in sex differences being more likely due to environmental change. One case of rapid
change in sex differences is human lifespan, which has become increasingly female-biased in recent
centuries. Long-term consequences of variation in the early-life environment may, in part, explain
such variation in sex differences, but whether the early-life environment mediates sex differences
in life-history traits is poorly understood in animals. Combining longitudinal data on 60 cohorts
of pre-industrial Finns with environmental data, we show that the early-life environment is associated
with sex differences in adult mortality and expected lifespan. Specifically, low infant survival
rates and high rye yields (an important food source) in early-life are associated with female-bias
in adult lifespan. These results support the hypothesis that environmental change has the potential
to affect sex differences in life-history traits in natural populations of long-lived mammals.