Neoteny is usually first learned in biology classes, studying the class Amphibians. Neoteny is a developmental delay in a number of species in which the possibility of sexual reproduction occurs before adulthood. Usually neoteny is considered on a living example of amphibians, worms or arthropods. But a number of anthropologists argue that man is also a product of neoteny.
The most famous example of neoteny
If in ontogenesis (this is the process of individual development) an organism lives in two environments (for example, in water and on land), then neoteny can contribute to the survival of the species. The larvae living in the water, after metamorphosis (transformation into an adult animal) go to land, as can be seen in amphibians (amphibians). If food is scarce on land, adults can die. But aquatic larvae are sometimes able to proceed to sexual reproduction, bypassing the stage of metamorphosis. This helps keep the look.
The axolotl is an example of neoteny given in all textbooks. This is a larva of an ambistome, a family from the order of caudateamphibians. They live on the North American continent in nature and around the world in aquariums of pet lovers.
Most of the ambystoma species do not pass the stage of transformation into an adult animal. At the same time, the external gills, so similar to curls, disappear; lungs appear, eyelids appear in front of the eyes. The axolotl, whose photo always evokes emotion, can turn into an adult, already less attractive individual. This requires a hormonal inoculation, which will start the stage of metamorphosis.
Neoteny is the engine of evolution
There is a neotenic hypothesis about the origin of the Skullless subtype. This subtype includes the lancelet, from which the study of chordates begins at school. There is a second subtype of chordates - tunicates. Their larvae, unlike adult tunicates, are very similar to the lancelet. It is possible that as a result of neoteny, the tunicate larvae switched to reproduction, giving rise to a new subtype of non-cranial.
There is an opinion, proposed by de Beer, that neoteny is the cause of the appearance of insects - the largest group of animals. Insects owe their origin to centipede larvae.
Botanists also tend to assume neotenic progress in the plant kingdom. For example, the transition from tree-like forms to grassy ones. Longline neoteny is the process of the appearance of annual grasses, when juvenile, lower tiers begin to multiply, which do not grow to tree-like, “adult” forms. L. A. Takhtadzhyan spoke about "breaking off" ontogenesis, that is, the preservation of juvenile (youthful) featuresin adult organisms. This process was the evolutionary basis for the emergence and development of angiosperms.
Where we come from
Many researchers - V. M. Artsikhovsky, E. Mayr, A. D. Takhtadzhyan - note that the main thing in the process of neoteny is not that the larvae begin to multiply, but that the adult stages retain the juvenile form. In the 70s of the XX century, B. Campbell proposed his version of the emergence of man - a delay in the development of a number of signs in monkeys led to the preservation of their childish features in a new branch of primates, human ancestors.
Man really resembles a baby chimpanzee more than an adult animal:
- features of the shape of the skull (weakly pronounced arches of the eyebrows, etc.);
- hair structure and its accelerated growth on the head;
- relative sizes of teeth and jaws;
- disproportionately enlarged cerebral hemispheres immediately after birth.
Ethological (behavioral) features of young and adult animals are also important. It is assumed that the curiosity and playfulness of the cubs is genetically fixed in a new evolutionary branch. Hominids (a family of progressive primates) were more sympathetic to partners who had childish behavioral traits.
A. Markov, in a book on human evolution, suggested that selection for friendliness (a childhood trait) could lead to juvenile thinking and a number of morphological (external) features. This reduced aggression within groups of hominids andcontributed to their progressive development.
Neoteny and its implications for evolution continues to be a subject of study. New ideas about the origin of the world, and in particular plants, animals and humans, appear even today. The classic axolotl examples (photo in the article) are complemented by amazing hypotheses about the appearance of our ancestors.