How brain size directly and indirectly influences vulnerability to extinction across 474 mammalian species was evaluated. Under current conditions, the constraints on life-history imposed by large brains outweigh the potential benefits, undermining the resilience of the studied mammalian species. Contrary to the selective forces that have favoured increased brain size throughout evolutionary history, at present, larger brains have become a burden for mammals.

Maternal effects have a great influence on offspring phenotype. In oviparous species, females can adjust offspring development by changing the levels of certain components of the egg (like yolk hormones, particularly androgens), thus buffering the impacts of environmental heterogeneity on the performance of their descendants. Several studies have reported short term benefits of high yolk androgen levels, but such high hormone levels can also entail some costs. In this research article it is...