Placental invasiveness and brain–body allometry in eutherian mammals

Brain growth is a key trait in the evolution of mammalian life history. Brain development should be mediated by placentation, which determines patterns of resource transfer from mothers to fetal offspring. Eutherian placentation varies in the extent to which a maternal barrier separates fetal tissues from maternal blood. We demonstrate here that more invasive forms of placentation are associated with substantially steeper brain-body allometry,...