This list has been limited to features in which humans differ in kind from other organisms. In addition, however, we are differentiated by significant differences in degree that directly reflect the defining "sapiens" attribute of the species. Most obviously, humans have a proportionately larger cranial capacity. This capacity requires an unusually large birth canal, which affects anatomical gender differences. Because our survival depends on the long-term development of the conceptual faculty rather than on programmed instincts, our newborn infants are more helpless than the young of most mammalian species, and the maturation period (from infancy to adulthood) is proportionately longer.