Re: Why is Homo sapiens hairless?
John Waters (jdwaters@dircon.co.uk)
31 Oct 1996 10:28:59 GMT
Rohinton Collins <rohinton@collins.prestel.co.uk> wrote in
article <01bbc6a7$0c67fc00$LocalHost@dan-pc>...
>
> > When a baby is carried in its mothers arms, there is a
> > change in its effective surface to mass ratio.
> Relative to what? To the baby floating in mid air?
Certainly not to a baby
> lying on the floor.
JW: Relative to a baby hanging on to its mother in the way
that ape infants hang on to their mothers. In the case of
ape species, the young infant generally hangs underneath
its mother when being transported. Air can circulate right
round the infant's body, which allows its body heat to be
transmitted to the outside air.
>
> Ever heard of thermoregulation? Anyway, the fur would
insulate the baby.
JW: Fur has very little insulation value per se. It is the
air trapped in the fur which provides the insulation. When
a baby hominid was carried in its mother's arms the fur
would be flattened, thus losing most of its insular
qualities. Theroregulation would have been limited because
early hominids would have been unlikely to have had any
more sweat glands than present ape species.
>
> > the
> > core temperature continues to rise the baby could die
of
> > heat-stroke. Fact.
>
> Fact? Again, ever heard of thermoregulation?
JW: Even today, babies left in unventilated cars have died
of heatstroke in hot summers. Remember, early hominids
lived in hot semi-equatorial conditions.
>
>
> What 'areas' of the female body' ? Again, fact? As far as
I was aware, the
> only areas where *extra* or *additional* subcutaneous fat
is laid down in
> female humans is on the hips, bottom and thigh.
JW: Yes, plus the breasts. In other words, where the baby
comes into direct contact with the mother when carried in
her arms, (normal when the baby is very young). Older
infants are carried on the mothers hips, where they come
into contact with the waist, bottom and thigh. Well done
Roh, you're getting there.
>
>>
> > The subcutaneous fat of the female leads to
evolutionary
> > pressure for less body hair in the female. This is the
> > present
> > situation. Fact.
>
> Just quit saying 'fact' will you? There is absolutely no
flow of logic in
> your last statement.
JW: Sorry about the facts Roh. Perhaps I am wrong about
this one. According to my information, females generally
have less body hair than males. It seems to me perfectly
logical to equate this lack of body hair to the fact that
females have 12 to 15 percent more subcutanous fat than
males.
>
> > In Chimpanzee and Gorilla species, the juveniles stay
with
> > their
> > mother and share her nest until adolescence. After
> > maturity, the
> > young males are driven out by the alpha male. Fact.
>
> Untrue. Chimpanzees enjoy a multi-male polygynous social
structure where
> the males are related to each other.
JW: I think you have misunderstood my meaning. I know all
about female exogamy, but that is not the point I was
trying to make here. What I was trying to say is that the
juvenile males can share family nests with their mother.
This happens with both Gorilla and Chimpanzee species.
After puberty, the males do not share the family nest with
their mother. Young males are also low ranking, and are
kept away from the females by the Alpha males.
In many hunter gatherer tribes the young males are
similarly prevented from sharing living quarters with the
females. In this sense, there is a parallel situation. As
they cannot gain warmth from close contact, this could
explain why the young males grow body hair after puberty. I
accept this is pure speculation, but it seems a reasonable
proposition.
John.
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