All good examples, but humans are relatively underdeveloped at birth compared to most mammals due to the necessity of limiting skull size to allow an easier bir

All good examples, but humans are relatively underdeveloped at birth compared to most mammals due to the necessity of limiting skull size to allow an easier birth. An infant cannot lift its own head or locomote for several months, for instance. Just like marsupials finish up outside the womb in a pouch, we have own external phase.