Nothing shows how much we have in common (descent) with other mammals than those three words. When a baby is hungry the baby knows what to do.
Or not. Apparently the mechanism of suckling is up for debate. It sounds funny but I like that science is out to understand the mysteries of obvious, common-sense things about nature, like how a baby extracts milk.
Alex Berezow at Real Clear Science has all of the juicy details.
Citation: David Elad et al. "Biomechanics of milk extraction during breast-feeding", PNAS, 24 March 2014, doi: 10.1073/pnas.1319798111
Article: How Do Babies Get Milk Out of Breasts? By Alex B. Berezow, RealClearScience