Re: AAT
J. Moore (j#d#.moore@canrem.com)
Thu, 28 Apr 94 12:28:00 -0400
Cm> NICHOLLS PHILIP A <pn8886@thor.albany.edu> wrote:
Cm> >> At what point did the nasal passages move from a vertical orientation
Cm> >>to a horizontal one, and what advantage did this give early hominids
Cm> in a
Cm> >>Savanah enviroment?
Cm> >Our nose looks the way it does because we have a flat face. Most other
Cm> >primates have snouts and the direction of the nasal passage is due to
Cm> >the fact that it sits on a snout that projects forward quit a bit.
Cm> How is this an advantage?
Cm> David Greene
Cm> cm315c09@nova.umd.edu
If you're serious about understanding evolution (of humans or anything
else), wipe the whole idea of features NECESSARILY being advantageous
from your mind. Many if not most features "happen" because they're tied
to other features which change, like the nose business. Such (what
shall we call them -- ancillary changes?) features MAY also be
advantageous, but often are not. All they HAVE to be is "not deadly".
These sorts of changes can also be things that are not advantageous at
one time, but become advantageous later. If you think of such things as
"lucky breaks" for the species, it may be clearer. For instance, in
hominids as compared to apes, the increased use of tools was probably
not incredibly advantageous at the start, in areas where pickings are
good (chimps in some areas habitually use tools to open palm nuts while
in other areas they bite them open; it's a "cultural" [learned]
difference). Our ancestors' habits and physical adaptations just
happened to lead to our abilities to use far wider varieties of
environments than apes, but this was years and years later (read
MILLIONS of years later). We were just part of a "lucky" group:
initially our adavantages were not overwhelming, but lead to
overwhelming advantage.
These types of changes also give rise to what some incorrectly claim as
the "law" of disadvantageous intermediates. Remember that one? it's an
AAT favorite that was hashed out here a while back. It's based on the
false idea that no new feature can survive unless it is advantageous,
and I've explained above why that view is incorrect.
Changes in the face are subtly interconnected, and are covered often and
thoroughly in real scientific literature, the kind that AAT fans (and
writers) like to ignore. Changing the posture of a species relative to
another (both hominids and African apes are likely a departure from the
posture of the CA, rather than either being the primitive condition)
changes many other features without regard as to whether the individual
features are in themselves advantageous. Our spine is a good example,
and our nose is another. Interestingly enough, the nose may be an
example of a feature which much later becomes an advantage, since it
helps warm and moisturize air heading to the lungs. This aspect wasn't
a huge advantage until we began going to (or THROUGH) and living in very
dry and/or very cold (& dry) environments. This meant that regions which
were effective barriers to travel for apes were no longer such a barrier
for hominids, even though the feature itself evolved quite accidentally
for completely unrelated reasons.
This sort of thing turns up a lot in evolution, but is often
misunderstood (even within academia but especially in more popular
science writing).
Hope this helps you see Philip's point.
Jim Moore
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