Neoteny is the slowing down of somatic development. The result is that reproduction happens in what was ancestrally a juvenile morphologic stage.

Humans have also been argued to be neotenous. As adults, we are morphologically similar to the juvenile forms of great apes. This paedomorphosis, if it is real (and there is a serious argument that it is not), would be neotenous rather than progenetic because our age of breeding has not shifted earlier relative to other apes; our age of first breeding is actually later than other apes. Our somatic development therefore has not simply slowed down while reproductive development has stayed the same: what happened was that our somatic development slowed down even more than our reproductive development.