The model included CD33rSiglec gene numbers as response, maximum lifespan and body mass as covariates.
We first examined the extent to which phylogeny of the species in our study influenced life-history evolution, including gestation period, weaning time, maturation time, maximum lifespan, growth, body weight, and metabolic rate (Table S6).
Maximum lifespan and average adult body weight were retrieved from the AnAge database.
Data regarding maximum lifespan and average adult body weight for mammalian species are from AnAge: the animal aging and longevity (http://genomics.senescence.info/species/) (de Magalhães and Costa, 2009).
The analysis showed that, for example, maximum lifespan strongly covariates with body weight (r = 0.47, P = 4 × 10−113, F-test), time to maturity (r = 0.71, P = 1 × 10−156, F-test), and other examined traits (Fig. 2).
Further study of the very long-lived but small naked mole rat (with a maximum lifespan of > 28 years and body size of only about 35 gm) showed that their fibroblasts exhibit an unexpected second level of contact inhibition, a property that may be a powerful aid in cancer suppression (Seluanov et al. 2009).
This trade-off results in great differences in growth rate, age at maturity, body shape, and maximum lifespan.
Extant mammals diversified dramatically, featuring more than 100-fold difference in species maximum lifespan, 100-million-fold difference in body mass and adaptations to both terrestrial and aquatic life as well as to powered flight and subterranean life.
The single variable regressions, summarised in Table 1, show that of the four variables tested, body mass and maximum lifespan are individually significant predictors of mitochondrial synonymous substitution rates: Species with greater mass, or longer lifespan tend to have slower rates of synonymous substitution.
Overall, a positive correlation was shown between the residual maximum lifespan and residual CD33rSIGLEC gene numbers (controlling for both body mass and phylogeny).
