Neoteny, derived from the German word Neotenie which literally means “young”), is a case of pedomorphosis which means that the adult form of a species seems to possess certain features that are normally seen only in the young or juvenile form of that particular species.
Biological growth and development stages in all members of a species are genetically fixed. But since in Neoteny, the biological timing of occurrence of certain growth features of an organism seems to blur, Neoteny has become one of the crucial topics of study in the evolutionary and developmental biology.
In Invertebrates showing Neoteny, the physiological growth and development are slowed down or delayed, but sexual maturity and reproduction occurs in the larval stage itself.
Neoteny is observed in Humans also. For example, Down’s syndrome is a Neotenic disorder in which the adults have a large face as compared to the rest of the body that is characteristic of human babies. Some characteristic Neotenous features are absence of hairs, small nose, large brain size etc.
also called juvenilization, is one of the three ways by which paedomorphism can arise. Paedomorphism or paedomorphosis is the retention by adults of traits previously seen only in juveniles, and is a subject studied in the field of developmental biology. In neoteny, the physiological (or somatic) development of an organism (typically an animal) is slowed or delayed. In contrast, in progenesis, sexual development occurs faster. Both processes result in paedomorphism. Ultimately this process results in the retention, in the adults of a species, of juvenile physical characteristics well into maturity and pedogenesis (paedogenesis), the reproduction in a neotenized state.
Neoteny is one of three dimensions of heterochrony, or the change in timing of developmental events: acceleration (faster) vs. neoteny (slower), hypermorphosis (further) vs. progenesis (not as far), and predisplacement (begins earlier) vs. postdisplacement (begins later).
The word neoteny is borrowed from the German Neotenie, the latter constructed from the Greek νέος (neos, young) and τείνειν (teínein, to extend). The adjective form of the word is either "neotenic" or "neotenous".