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.

In recent years, I have heard the term "neoteny" used in a slightly metaphorical sense, to refer to the continuation of adolescent traits of human beings into adulthood.

The situation should be clear enough, even in its rough, stereotyped form, to anyone of us born after 1960 and living in a first world country. At one time, young people would graduate high school, get a job in manufacturing, marry, and pretty much live a life of adulthood from the age of 25 until their death. Now, young people go to graduate school, get part time jobs, marry later, move around, go back to graduate school again, and carry on a fascinating with music, entertainment and other such frivolities into a permanent way of life. And this way of life is not, stereotypes to the contrary, confined to the thirty year old loser, sitting in his parent's basement, taking bong hits and watching a Smurf's Marathon. Hailing (at times) from Portland, Oregon, I have witnessed first hand doctors, lawyers, school teachers and plumbers in their 40s and 50s indulging an obsession with cupcakes, costume parties and David Byrne. The age of permanent adolescence, while perhaps fueled by a weak economy and a generational ethic of irony, is about something much bigger.

One of the hallmarks of a young organism is that it likes to play and learn. As an individual approaches adulthood, its hunger for play, and its ability to learn, both decline. Around the age of four or five, most housecats stop being fascinated by a ball of string. For many generations, around the age of 25, most humans stopped being fascinated by the hominid equivalent. But now, a youthful attitude, and the ease of learning and adaptation that come with it, might become a permanent part of human life. This may be need driven: in the modern world, humans have to adapt to everything from new operating systems to colleagues from different culture. Or it may be opportunity driven: with an increased amount of leisure time, people have the chance to live a more fun life than they did in the past. But in either case, the change seems to be here.

So what seems to be a sociological hiccup could be something much greater. The simplest chordata, the sea squirts, have a brief phase of motility, after which they find a rock to attach to, followed by the loss of their nervous system and a life as a filter feeder. There is a theory that the rest of the chordate phylum, starting with lancets and eventually leading to pterodactyls, koala bears and humans, evolved because some of these early chordates didn't mature, but instead stayed in their early, mobile phase. The increasingly-older-young-people of today are perhaps not just shiftless hipsters, unable to shake their adolescent obsession with music and looking cool: they are the equivalent of the chordates who refused to become filter feeders, and they may spark just as much of a burst in evolution as their Cambrian cousins.

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