Link. Similar to adolescent pruning of key neural networks. Suggests optimizing or locking-in some bonding behaviors that favor infant survival. (But may decrease maternal survival. )

“By the ninth week of gestation, 80 percent of 400 brain areas analyzed showed decreases in gray matter volume and cortical thickness that continued through pregnancy, with areas shrinking by 4 percent on average. Change was particularly pronounced in the default mode network, which is instrumental in perceiving other people’s feelings and perspectives.”