Re: AAT reply from Elaine Morgan

Pat Dooley (
2 Jan 1995 22:22:09 -0500

>Humans and baboons have not shared a common ancestor for more
>than 35 million years. It is therefore unlikely that hominids
>moving onto a savannah environment would adapt to the savannah
>like baboons.

<< deletions>>

The point you keep missing is that every savannah animal shares some
basic characteristics. For example, except for the very largest, they are
hairy. The physiological explanation for that is that fur facilitates
sweating, provides insulation during cold savannah nights, and protects
against solar radiation. Every savannah animal conserves water and
since water is a scarce resource and water holes are dangerous places.
Every savannah animal at risk from predators can run faster than any human
and they can do it almost from birth. Baboons and Patas monkeys are
far faster than humans and retain the ability to climb rapidly.

On all these counts and many more besides, humans are different.

>Apes, be contrast, did not develop these specialized locomotor
>adaptations. For all living apes, the forelimbs are longer than
>the hindlimbs.

I suspect you've forgotten the most common ape species. Or do
you stll knuckle-walk?

>short olecranon processes on the ulna, have a more generalized
>wrist morphology and on the whole tend to walk bipedally more
>than monkeys. When terrestrial, orangutans "fist-walk" while
>gorillas and chimpanzees "knuckle-walk." All of the present

You persist in labelling these modes of locomotion as bipedal.
Bipedalism in the human sense involved major anatomical changes
that are not seen in any other ape species.

According to Richard Leakey and Roger Lewin "the evolutionary
shift from quadrupedalism to bipedalism
would have required an extensive remodelling of the ape's bone
and muscle architecture and of the overall proportion in the lower
half of the body. Mechanisms of gait are different, mechanics of
balance are different, functions of major muscles are different.
An entire functional complex had to be transformed for efficient
bipedalism to be possible." cf. "Origins Reconsidered". For your own
edification, you might care to compare the skeletons of the
major ape species, mounted n their natural locomotive position.
Pay particular attention to the pelvis, the curvature of the spine,
the knees, and the position of the skull relative to the spine.
There is some major re-engineering required to get from the
proto-homind/ape model to the human model.

About all you€ve demonstrated so far is that apes, under the
right evolutionary pressure, would be more likely to develop
bipedalism than pure quadrupeds. Your post about Bonobos
was quite instructive.

>mention sweat glands and this is another example. Monkeys have
>few eccrine glands while apes in general have a 50/50 distribution.
>Therefore monkeys moved onto the savannah without the advantage of
>sweat as a heat rejection system. As a result, baboons do not
>move about much during the hottest part of. If we assume
>that protohominids had at least a 50/50 distribution then it
>would seem they had the mechanism for sweating mostly in place.
>AS above, they have different sets of baggage and therefore
>adapt differently.

You make the fundamental mistake of assuming that eccrine glands
are sweat glands. In every sweating mammalian species, except one,
the acropine glands are used for sweating. No prizes for guessing
the odd one out. So far as I know, no other ape sweats, even when
subjected to extreme heat under laboratory conditions. Humans,
as you well know, have a 99/1 distribution of eccrine/acropine
glands that puts them well off the ape norm. If they had gone
directly from the forest to the savannah with your 50/50 distribution,
then 100 million years of mammalian evolutionsays that
humans would have evolved acropine sweating if they
needed to improve their heat dissipation mechanism. The fact they
evolved a new sweating mechanism based upon eccrine glands
strongly suggests they lost the other 98% of their acropine
glands BEFORE sweating evolved. As you said, in as many words,
nature doesn€t evolve new pathways when it can build on old ones.

>This is why I have stated repeatedly that the "Why don't baboons
>do it ...?" kind of argument is bogus. Convergence may occur,
>given enough time and strong enough selection pressures but if
>you look at all the examples you have cited of convergence they
>have all required much more than the 2 million years of time you
>have open in the AAH. Evolution must work with materials at hand
>and in general acts divergently, rather than convergently.

You may have read the recent book about finch evolution in the Galapogos
Islands. I think it is a safe bet to say that different finch species on
islands would have evolved similar bills in response to similar
pressures. Convergence at that level, took decades, not 2 millon years.
Let€s take another topical example. Since wolves have been wiped out
of the US NorthEast, coyotes have stepped into the ecological niche
left by wolves. Biologists have been somewhat fascinated to find that
coyotes in this region are becoming, in not very many generations,
significantly larger than other coyotes in other parts of North
America. It rather suggests convergent evolution in a very short
time frame - the scavenger becomes the hunter and takes on
its adaptations when the hunter disappears. Lets try another example that
fits within your 2 million year time frame. The Egyptian Water Buffalo,
in common with many aquatic and wallowing animals, has lost most
of its acropine glands. It has only 1/10 as many as cattle, members of the
same family.

I quite agree that evolution works with the materials at
hand. The divergence comes in when species radiate to occupy
different ecological niches. When different species occupy the same
ecological niche, you get convergence. Both occur in similar time scales -
ranging from decades to millions of years.

Pat Dooley