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. In marsupials, an energetic constraint on brain size in (...) adults is only revealed if we consider both metabolic and reproductive rates simultaneously, because a strong trade‐off between encephalization and offspring production masks the positive correlation between basal metabolic rate and brain size in a bivariate comparison. In conclusion, starting from an energetic perspective is warranted to elucidate relations between ecology, social systems, life history, and brain size in all mammals. (shrink)

An unprecedented level of confidence has recently crystallized around a new hypothesis of how living placental mammals share a pattern of common descent. The major groups are afrotheres (e.g., aardvarks, elephants), xenarthrans (e.g., anteaters, sloths), laurasiatheres (e.g., horses, shrews), and euarchontoglires (e.g., humans, rodents). Compared with previous hypotheses this tree is remarkably stable; however, some uncertainty persists about the location of the placental root, and (for example) the position of bats within laurasiatheres, of sea cows and aardvarks within afrotheres, and (...) of dermopterans within euarchontoglires. A variety of names for sub‐clades within the new placental mammal tree have been proposed, not all of which follow conventions regarding priority and stability. More importantly, the new phylogenetic framework enables the formulation of new hypotheses and testing thereof, for example regarding the possible developmental dichotomy that seems to distinguish members of the newly identified southern and northern radiations of living placental mammals. (shrink)