head growth several years after birth. This particular type of heterochrony, hypermorphosis, involves a delay in the offset of a developmental process, or what is the same, the presence of an early developmental process in later stages of development. Humans have some 30 different neotenies in comparison to the chimpanzee, retaining larger heads, smaller jaws and noses, and shorter limbs, features found in juvenile chimpanzees. Related concepts The term "heterokairy" was proposed in 2003 by John Spicer and Warren Burggren to distinguish plasticity in timing of the onset of developmental events at the level of an individual or population. See also Ontogeny and Phylogeny References See also Developmental biology Embryogenesis Evolutionary biology Phylogeny Developmental biology Evolutionary biology concepts Evolutionary developmental biology