Re: Evolution doesn't "force"...

Paul Crowley (
Wed, 04 Oct 95 10:10:38 GMT

In article <> "J. Moore" writes:

> Cl> At this point you have a modern chimpanzee which has survived to the
> Cl> current day, what more changed to force the proto-hominid to go beyond
> Cl> the chimpanzee mode of existence?
> Cl> Tom Clarke
> You seem to be making a common but incorrect assumption. I would
> guess you don't realize that the question you ask here is a
> non-evolutionary one: "what forced them to change?" Change happens
> during evolution, and nothing need "force" it.

As a "new kid on the block" this is exactly a point that I was going to
make. I've been seeing this error everywhere in the paleoanthopological
literature, on both sides of the AAT debate, and committed by the most
eminent and respectable people. It's so common that I was finding it
difficult to decide whether it was me or them.

The current (1995) Encyclopedia Britannica has the following in an
article by Professor Bernard Wood (vol 18, page 821d):

"Thus it may be that the drier climate forced the robust australo-
pithicines to occupy a specialised - and ultimately limited - niche
in the sparsely wooded savannah grasslands."

As you say evolution forces nothing. If its habitat changes the species
will die. If another habitat was already present, and the species was
not already exploiting it, it's not going to be "forced" into doing so
by an ecological change. Yet this error seems to have been basic to the
savannah or savannah/mosaic hypotheses. (We can talk in the past tense
now, can't we?) It was also common in the AAT. The flooding of the Sea
of Afar "forced" the apes isolated there into a new form of life. It's
desication "forced" them to re-adapt to land.

Here's are some examples culled from postings to this group:

David L. Burkhead
29 Sep 1995 21:12:15 GM
Subject: Re: AAT Theory
> Situation changes slightly. The arboreal ape has to spend more
> time on the ground. For reason, perhaps the forests are thinning and
> it has to drop to the ground to get to the next tree or perhaps a
> stronger competitor has come along to force it either down to the
> ground or out to less densely forested regions.

Phil Nicholls
28 Apr 1995 00:27:41 GMT
> As conditions
> became drier and forests began to shrink these peripheral
> environments became less optimal. It probably began short
> excusions out onto the savannah. Perfection of bipedalism
> enabled longer excursions and eventually, by the time of Homo
> habilis, occupation of savannah environments.

Quoted by J. Moore
Mon, 26 Jun 95 10:13:00 -0500
> From: Leon P. Lumiere
> Chapter 3. "The Evolution of Genus *Homo*: Where It Happened" pg. 27:
> The dwindling forest would produce exactly the environmental conditions
> required by the Hardy hypothesis; those apes near the coast, losing
> their forest, gradually would be forced into water to find both food and
> protection from predators.

Elaine Morgan"
Thu, 17 Aug 1995 15:24:58 GMT
> > 1. If the ape did so well out of the sea, why did it levae it?
> The sea left the ape ; it became unlivable in and evaporated.

Pat Dooley
9 Jul 1995 19:51:51 -0400
> The first stage roughly corresponds to the geological evidence for
> the Sea of Afar. What sort of selective gradient would the sudden
> formation of a large sea impose on those creatures trapped on islands
> in that new sea? Fairly drastic, one would think.

Alex Duncan
9 Jul 1995 17:15:21 GMT
> Gibbons and spider monkeys rarely come to the ground, because
> they're not terribly good at moving there, and because their food sources
> are all arboreal. But, what would happen if there were a climate change
> and the environments these creatures live in were to become a little less
> lushly tropical? What if the patches of trees were separated by short
> distances of open space. Would these creatures suddenly adopt
> quadrupedalism to move from one patch of trees to the next, or would the
> efficiency of their already existing mode of terrestrial locomotion
> increase?