Neoteny

Neoteny is a term in developmental biology that describes the retention of juvenile characteristics in the adults of a species and is similar to but not the same as progenesis, which is the attainment of sexual maturity by an organism still in its larval stage, as is found among certain amphibians and insects. The word itself is derived from the Latin neotenia, which is a composition of the prefix Greek neo- meaning "young" and the teinein to extend.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In humans neoteny is manifest in the paedomorphic characteristics exhibited by fertile women. See Sexual attraction

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In the animal kingdom, progenesis is sometimes induced by environmental conditions that inhibit the completion of metamorphosis, such as low temperature or lack of available iodine leading to low thyroid gland activity. The larval form may mature sexually, mate, and produce fully viable offspring. If environmental conditions improve, this particular kind of progenesis can sometimes be reversed, with the larvae completing metamorphosis and attaining normal maturity.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

One example of neoteny in vertebrates is the salamander species axolotl, which usually remains fully aquatic as it matures. However, a more famous example is the Giant Panda, an animal that retains its baby like cuteness into adulthood.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In insects, reproduction in the larval stages is known as paedogenesis; it occurs in the females of certain beetles, Strepsiptera, bagworms, and gall midges. In the midges, the daughter larvae produced within a mother larva consume the mother and escape; the process may continue for several generations.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Neoteny also plays a role in evolution as a means by which a species can undergo a significant physical change. In such cases a species' neotenous form becomes its "normal" mature form, no longer subject to environmental triggers to induce or inhibit maturity. The mechanism for this could be a mutation in a gene involved in maturation, inhibiting its function. Examples of species that may have undergone neotenous changes in the course of their evolution include flightless birds (their proportions resemble those of the chicks of flighted birds), humans (who have sparse body hair and enlarged heads reminiscent of baby primates), and dogs (who share many mannerisms and physical features with the immature wolf). Obviously neoteny is not the only contributing factor to the evolution of these species, and its actual involvement is still not well determined.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Developmental biology: Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and "morphogenesis," which is the process that gives rise to tissues, organs and anatomy....

Species: In biology, the most commonly used definition of species was first coined by Ernst Mayr. Species are "groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups" (however, see other definitions of species below)....

Progenesis: Progenesis is a term in developmental biology referring to the attainment of sexual maturity by an organism still in its larval stage, as is found among certain amphibians and insects. It is similar to neoteny....