Re: Why is Homo sapiens hairless?

Joel Hanes (
27 Nov 1996 22:01:51 GMT

Re: Why is Homo sapiens hairless?

Well, first: IIRC most humans have about the same number of hairs
per square inch of skin as do other primates -- the
hairs tend to be fine and pale on the human body,
and coarse and dark on chimpanzees of the the first
and second types.

So, then: why do humans mostly have fine pale body hairs?


Mate-recognition signals are in many species a strong
force maintaining the separateness of closely-related

For example, North American Pintail and Mallard ducks
are known to yield fertile hybrids, but such hybrids are
extremely rare in the wild. Males of both species have
distinctive bright-colored plumage: the mallard drake has
a glossy green head and a dark chestnut front,
while the pintail drake has much white fore and aft.
Both drakes have modifications of the tail feathers:
the mallard has several strongly back-curled feathers
at the base of the tail, while the central tail feathers
of the pintail drake are drawn out into an obvious
spike. The hens of both species are less gaudy,
but likewise have very distinctive plumages.

I claim without evidence that these distinctive
patterns (and other differences, like the amazing
difference between the mallards' quack and the pintail
whistle) arose and are maintained by sexual selection,
and that mate-recognition signals serve as the primary
reproductive barrier between these species, (as it
seems to in many wetland birds).

It's my belief that sexual selection for mate-recognition
signals similarly powered much of the human speciation
process, and continues to serve as a powerful selective
pressure in our lineage today.

I think that our hair patterns, protruding breasts and
buttocks, small flat faces, mild sexual dimorphism,
and relatively large penises are among the morphological
characteristics selected for.

A thought experiment:

Do you find all members of the appropriate sex equally attractive?

Do you find reconstructions of Lucy sexually attractive?

Think about the physical characteristics that you find
particularly attractive in a potential mate:
Are any of them shared by other living primates
in the same age and condition?
Are any of them shared by Pan paniscus?
by Lucy?
by Homo erectus?
by Homo sapiens neaderthalensis?

Joel Hanes SP4