Data from: The sex with the reduced sex chromosome dies earlier: a comparison across the tree of life

Many taxa show substantial differences in lifespan between the sexes.
However, these differences are not always in the same direction. In
mammals, females tend to live longer than males, while in birds, males
tend to live longer than females. One possible explanation for these
differences in lifespan is the unguarded X hypothesis, which suggests that
the reduced or absent chromosome in the heterogametic sex (e.g. the Y
chromosome in mammals and the W chromosome in birds) exposes recessive
deleterious mutations on the other sex chromosome. While the unguarded X
hypothesis is intuitively appealing, it had never been subject to a broad
test. We compiled male and female longevity data for 229 species spanning
99 families, 38 orders and eight classes across the tree of life.
Consistent with the unguarded X hypothesis, a meta-analysis showed that
the homogametic sex, on average, lives 17.6% longer than the heterogametic
sex. Surprisingly, we found substantial differences in lifespan dimorphism
between female heterogametic species (in which the homogametic sex lives
7.1% longer) and male heterogametic species (in which the homogametic sex
lives 20.9% longer). Our findings demonstrate the importance of
considering chromosome morphology in addition to sexual selection and
environment as potential drivers of sexual dimorphism, and advance our
fundamental understanding of the mechanisms that shape an organism's
lifespan.