Recently, Weisbecker and Goswami presented the first
comprehensive comparative analysis of brain size, metabolic
rate, and development periods in marsupial mammals.
In this paper, a strictly energetic perspective is
applied to identify general mammalian correlates of brain
size evolution. In both marsupials and placentals, the
duration or intensity of maternal investment is a key correlate of relative brain size, but here I show that
allomaternal energy subsidies may also play a role.