Retention of juvenile traits

Neoteny (/niːˈɒtᵻni/ /niːˈɒtni/ or /niːˈɒtəni/, (also called juvenilization) is the delaying or slowing of the physiological (or somatic) development of an organism, typically an animal. Neoteny is found in modern humans. In progenesis (also called paedogenesis), sexual development is accelerated.

Both neoteny and progenesis result in paedomorphism (or paedomorphosis), a type of heterochrony. Some authors define paedomorphism as the retention of larval traits, as seen in salamanders.

Both neoteny and progenesis cause the retention in adults of traits previously seen only in the young. Such retention is important in evolutionary biology, domestication, and evolutionary developmental biology.

The origins of the concept of neoteny have been traced to the Bible (as argued by Ashley Montagu) and to the poet William Wordsworth's "The child is father of the man" (as argued by Barry Bogin). The term itself was invented in 1885 by Julius Kollmann as he described the axolotl's maturation while remaining in a tadpole-like aquatic stage complete with gills, unlike other adult amphibians like frogs and toads.

...
Wikipedia