Re: Why is Homo sapiens hairless?

Rohinton Collins (
20 Nov 1996 23:29:26 GMT

I believe the process you are referring to Jose, is called Neoteny. It is
an evolutionary biomechanical process thought to facilitate changes in
morphology, where the adult phenotype resembles a more juvenile phenotype
of an ancestral species. I can elucidate better with an example: the chimp
or LCA or australopithecine adult cranial morphotype is a large face with
respect to the cranium (about the same size). However juveniles of these
species (including the foetuses) have a relatively small face wrt the
cranium. So neoteny has acted to decrease the size of the face wrt the
cranium in later hominid species, where an adult skull resembles a more
immature skull (in proportion) of an ancestral species.

However, neoteny is just a biomechanical pathway dictated by evolution.
That is, if evolution 'selects' a smaller face (for whatever reason),
neoteny is the process by which the adult morphotype is altered. This does
not mean that we (as hominids) arbitrarily adopt phenotypes from juvenile
stages in ancestral species. A phenotype must be selected for, for a



Jos€ Herculano <> wrote in article
> The protection afforded by hair is so frail that it would really be
> to derive an adaptive trend from it, either way.
> The best explanation that I have ever heard has nothing to do with a
> effect relationship, but with a lateral process:
> Human infants, due to the known pelvic problems associated to our larger
> brain, are born in a very immature state. That trigged immaturity
> we keep infantile behavior (in relation to the other higher-primates)
> throughout
> our lives - curiosity, playfulness, etc.
> An immature chimpanzee fetus has no body hair. By the known genetic
> process that keeps us immature in relation to our cousins, we can explain
> do we have so little body hair.
> --
> Jos€ Herculano