The human pattern of growth and development (ontogeny) appears to differ markedly from patterns of ontogeny in other primate species. Humans present complex and sinuous growth curves for both body mass and stature. Many human proportions change dramatically during ontogeny, as we reach sizes that are among the largest of living primates. Perhaps most obviously, humans grow for a long time, with the interval between birth and maturation exceeding that of all other primate species. These ontogenetic traits are as distinctive as other key derived human traits, such as a large brain and language. Ontogenetic adaptations are also linked to human social organization, particularly by necessitating high levels of parental investment during the first several years of life.
