Re: The straw man.

David Froehlich (
Wed, 18 Oct 1995 17:34:56 -0500

On 18 Oct 1995, Thomas Clarke wrote:

> > Many of these were simplistic, focusing on a single behavior such as
> > food carrying or intimidation. What these hypothesis have in common
> > with later hypothesis is that they propose the following scenerio:
> > [1] Preadaptation = most primates can walk bipedally. Apes are the
> > most bipedal of all primates with chimpanzees reported to engage in
> > bipedalism something like 10-11% of the time they are on the ground.
> OK.
> > This means that the common ancestor was at least as proficient at
> > bipedalism as living apes and may have been more so as they had not
> > yet become knuckle-walkers.
> This does not follow.

I would argue that this is the parsimonious scenario. Why posit a change
in environment. It may come down to a preconception one way or the other
about how hard it is to develop bipedalism (which I certainly come down
on the easier side). At least my take on the difficulty of bipedalism
rests on the condition among the outgroups (positionally upright,
obligate to facultative bipeds) and I see no great problem. The
arguement above rests on the parsimonious idea that knuckle walking is an
autapomorphy, therefore the last common ancestor was probably not as good
a quadruped as chimps and gorillas (and it has laready been pointed out
how ineficient chimps and gorillas are as quadrupeds.

> > [3] Biological Changes = simply put, morphological changes follow
> > behavioral ones.
> Only if the changes result in increased reproductive success.

They do not actually have to be advantageous, just not deleterious.

> > Hence the role of the savannah is important to all of these scenerios
> > because it provides a transition from an arboreal to a terrestrial one
> It is not the only possible transition.

Just the one that seems to be more plausible

> > and because hominid fossils are found in association with
> > savannah-woodland environments.
> ^-riverine

Fossils are found in fluvial settings by and large. This is a taphonomic
constraint that cannot be utilized to imply a riverine existence (note
all the horse, elephant, giraffe, suid fossils that co-occur). We are
unlikely to ever find the total savannah fossil sites that AAS seems to
expect out of the SMS (savannah mosaic scenario) because fossils are
largely not preserved there and these settings tend to be in
degradational rather than aggradational geologic contexts.

> > ANY explanation of hominid
> > evolution must involve the savannah because it is obviously important
> > to our evolutionary history.
> Of course. The AAT/H/S fully acknowledges the importance of the
> environments in which hominds actually lived which clearly
> involved the savannah post A.a.

Assuming that this period actually ever existed.

> > This does not justify taking all of
> > these explanations and calling them the "Standard Savannah Theory."
> > Do do so is a classic strawman exercise which is why myself and others
> > have called you on this.
> Wait a minute, you just went through a whole argument about how
> "ANY...must involve the savannah".
> Call it what you will, but it sounds like a theory to me and it
> pointed excludes the possibility of the role of a non-savannah
> environment.

The ancestors lived in savannahs and the descendants lived in savannahs
so what is the problem. Why assume an ecologic change when there is no
evidence for one?

> > There are almost as many explanations for the evolution of various
> > aspects of hominid morphology as there are paleoanthropologists -- a
> > large but finite number. Yours is certainly no worse than some but
> > that is not saying a lot. If you really want to impress people I
> > suggest you spend less time complaining about ill treatment and more
> > time proposing a way to test the AAH. If it is not testible I am
> > afraid it doesn't even deserve the "H".
> Not testable, falsifiable is the criteria from the philosophy of science.
> The AAT/H/S is certainly falsifiable, just find some 5 and 6 million
> year old fossils in the hominid lineage that clearly were not dwelling
> in association with water.

As I explained above this is unlikely to happen, and given the tenor of
the pro AAS discussion, I have serious doubts whether it would even be
accepted. Shouldn't the AAS go about attempting to strengthen it own
case by failing to falsify its own predictions (tears, diving reflex,
functional constraints of bipedality, energetic cost of bipedality vs.
knuckle walking, energetics of mammire mammals compared to hmans, etc.).

It seems that what AAS people desire is a smoking gun that probably
cannot ever be found. (Blow away the straw man savannah arguement
and what happens? it gets replaced by another one).

David J. Froehlich Phone: 512-471-6088
Vertebrate Paleontology Laboratory Fax: 512-471-5973
J.J. Pickle Research Campus
The University of Texas, Austin, Texas 78712