|
|
Bi-paedalism and Hair loss connected.
Mark Shuttleworth (insight@iafrica.com)
19 Sep 1996 09:07:52 GMT
Sedcon
Socio-economic Development Consultancy
PO Box 13188
Mowbray
7705
South Africa
Tel +27 21 689-1687
E Mail insight@iafrica.com
The Editor
South African Journal of Science
PO Box 61019
Marshalltown
2107
South Africa
Bi-paedalism
Previously Un-published letter to SA Journal of Science Dated 8 June 1990
I found the article by Mrs R Eickhoff, on the origin of Bi-paedalism in
your Volume 84 June 1988, most interesting. I had for some time been
pondering this subject, since having disagreed with the conclusions of
Professor PV Tobias, on the matter of hair loss in the pre-human line. I
felt the two were inextricably linked, but with a lack of detailed
knowledge of paleo-anthropology, have had difficulty formulating my ideas,
to my satisfaction.
Professor Tobias' article in your Volume Issue ,postulates that a
need to ventilate and cool more efficiently, caused a change in the ratio
of the two types of sweat glands, and hence the almost complete loss of
hair on our ancestors. I can accept this, if it can be demonstrated that
the climatic conditions at that time were so severe, that other species
which also populated the open savanna, and which did not undergo a drastic
change such as our ancestors loss of hair, had perished. In addition it
would have to be demonstrated that not only did we lose our hair, but that
other changes in anatomy of habits, had taken place to assist in the
combating of the problem of overheating.
The reason I say this, is that if one considers a situation where there are
certain variables, and a point of equilibrium has existed at some stage,
where the one variable dominated very much over the other; a change which
would bring about a process of gradual adaptation to the changing
environment, is highly unlikely, to re-establish a point of equilibrium, at
the remote end of the spectrum or range of possibilities. In practice this
is where we , as what Desmond Morris refers to as, "naked apes", stand at
the moment. Which other mammal inhabiting the savanna now, or as far as we
know in the past, stands, or has ever stood, anywhere near this point; in
the ration of two sweat glands, or whatever would effect the nature of hair
in that particular mammal?
At the midpoint in the spectrum a certain change in ration of two sweat
glands from say 1 : ( x + y1) would benefit the primate by 1 degree
Centigrade. However as the process progressed, 2y1 would not produce 2
degrees centigrade but slightly less and so on, i.e. e y2 would be > 2y1;
and for T degrees at the most remote end of the range, yt would be such
that any increment thereof , would produce negligible increase in benefit.
We know this from our own experience. Males very greatly in hairiness
without difference in resistance to heat, and yet women with long hair, and
men with beards know that localised presence or absence of hair in large
amounts is a definite factor.
Was there a sudden mutation? My knowledge of genetics does not assist me to
answer that one in any manner whatsoever. What I can look at however, is
the consequences of the loss of hair, complete as it has been. There would
have been a need to keep warm, hence the use of shelters, clothing , and
fires. Far away the most serious problem as far as I am concerned, was the
danger of extinction due to the loss of off-spring. Babies, because of the
higher ration of surface to volume, as against adults; would have been
seriously vulnerable to death by exposure. The mother with no hair would
have had difficulty cuddling her new-born child. Furthermore, she would
have been unable to carry the child beneath her, as other primates do. The
extraordinarily powerful grasp of a new-born human baby, indicates to me
quite clearly; that our ancestors in the pre-hairless state, carried their
babies on their stomachs, by means of the clutching by the baby of the
mother's hair. Other primates, when their off-spring are somewhat older,
permit them to clamber on to their backs, and balance themselves there
quite happily.
The question is, could it possibly have happened, that by a process of
natural adaptation; the baby would have gradually worked its way round to
the back? I would think this is a quite ridiculous supposition. Somebody
had to stop and think. Someone had to be greatly concerned, at a baby
attempting to cling to the tummy, failing and falling off. Someone had to
say' "Why not on my back? The child can cling to the hair of my head and
sit astride".
Could loss of hair have led directly to Bi-paedalism? Adrienne L Zihlman
and Bruce A Cohn in your Volume 82 Feb 1986 issue, in referring to loss of
hair, and changed pigmentation of our ancestors; state "This complex of
features, we propose, evolved along with other anatomical changes,
especially Bi-paedal locomotion". As I shall demonstrate later, my theory
of hair loss fits very well into this. The article of Mrs Eickhoff would
seem to present problems. However I am satisfied this is not so , as she
postulates Bi-paedalism in different forms and along different evolutionary
lines. I probably makes thins easier for what I now suggest.
This partially Bi-paedal mother, using a burgeoning reasoning, would have
decided to place her child on her back at birth. The child would have clung
to the hair of her head and attempted to grip something with its little
feet, the soft tummy hair and soft tissues below the rib cage would have
had no counter-part on the back completely hairless and firm as it would
then have been. What was mother to do? The answer was to slip one arm freed
from the need for walking behind her back and steady the little one's bare
bottom therewith. If still holding her body horizontal, holding baby thus,
would have been less easy than if more erect. This would not have
completely solved her problem, unless she became or was already Bi-paedal,
and either erect of more probably at that stage, only partly erect. One way
or another at any rate, by this process some babies would have survived.
That mother's problems were not over by any means! The little baby would
not as easily have been carried in such a manner than in a completely erect
position. Was she thus to be doomed to walking semi-erect for the rest of
her evolutionary career? Then there was the further problem of the child
defecating and urinating over its mother's back and upwards bent steadying
arm. Much better to cradle the child against one's breast with one arm, and
walk upright as women do to this very day. In this position, modern mothers
find that the moment the child tenses itself to either defecate or urinate,
( and in fact do almost anything else, even turn and look at a stranger),
they sense it. The child can then be held out, and the chances of becoming
messed up, of the mother and of the child itself in fact are, are reduced.
Having carried the baby for nine or so months, beneath her heart, she now
cradles it against her breast, where it is warm and safe and close to it's
food supply. Mother must now however walk erect, and learn to forage with
one arm only. Long head hair, will still be useful, as it was when she held
it on her back.
G V G Shuttleworth
|