Having the physical characteristics of immature members of most species. Often characterized by large and watery eyes, large heads on small bodies, small noses and mouths, and high pitched voices. Often encompassing the very definition of cute, neoteny can stimulate a protective or nurturing instinct in adults which might otherwise threaten it.

Since neoteny is common in the very young, species that retain immature characteristics into their adulthood find it useful as a survival mechanism.

Many cartoon characters have evolved more neotonous features over time in order to increase their appeal. Examples: Mickey Mouse, Bugs Bunny, and anything invoving "baby" characters (i.e. Muppet Babies, Scrappy Doo, etc.)

See also super-deformed.

A concept from evolutionary biology: basically that sometimes organisms adapt by not fully maturing or that evolution makes use of what was an incompletely developed phase in an evolutionary ancestor's development as the adult form of a new organism.

Examples include the axlotl, a Mexican salamander which (under the pressures of a hot, arid terrestrial environment) stays in a "tadpole" like stage, remaining fully aquatic throughout its life cycle. Also, human evolutionary development is said to example neoteny. Higher primates, and in fact many simians less intimately related to humans genetically, have young whose still not fully developed and specialized forms are more strikingly human-like than their adult counterparts, having juvenile characteristics such as larger (proportionally) eyes, flatter faces with less snout-like protrusiveness, and rounder heads and faces generally. Human evolutionary development is thought to have adopted these forms as the traits of adult organisms, lumped in along with the prolonging of infancy and childhood which allows for the much heightened demands of human mental development.

The term is also evoked in discussion of depictions in art, notably the anthropomorphic, neotenic forms of cartoon animals and animated characters in advertisements, where the infantile characteristics (particularly the large, round eyes and proportionally shortened arms and legs) are exaggerated to evoke an instinctive emotional response from human viewers who subconsciously associate exaggerated neoteny with human infants, to whom they are instinctively hardwired to pay attention. Much anime also makes use of this formula, see kawaii.

Neotony is that device which, anthropologists say, gave early hominids the evolutionary edge over established savannah carnivores like lions and wild dogs.

Since animals have the highest learning curves of their lives when they are infants, if humans were to retain a child-like brain structure throughout their lives they would have a learning curve no other creature could approach. And an infantile brain structure also involves an infantile skull structure, which includes a forward-facing, rather than upward-facing, orientation of the head. This is one of the things that, anthropologists say, contributed to our famous species-wide erection – er, erect stance.

Our feet, which lack a prehensile thumb-toe, is also commonly attributed to neotony. It was a way to help us walk erect, thus supporting our foetus-like heads and also to help us run faster, which is an asset when you have lions after you.

Some of the side-effects of neotony include relatively hair-free bodies (for primates) and small teeth, which are useless for fighting or even for intimidating.

And, of course, our species-wide predisposition to wet ourselves.