Re: Refs, please... was... Re: AAT Theory

David Froehlich (
Sat, 21 Oct 1995 16:14:29 -0500

On 20 Oct 1995, H. M. Hubey wrote:

> Both MSS/SSS posit an environment change. it seems that what
> you are doing now is merging the forest, the grasslands and
> the "mosaic" (whatever it means by now) and creating a mess.
> If nothing changed, then there'd be no niche to fill. There'd
> be no split. At least the original SSS posits that the change
> was from forest-dwelling to savannah/steppe/grasslands-dwelling.

Funny thing, we have evidence from the fossil record that this change
actually occured. Why is it so difficult to accept? I think you
misunderstood slightly, in that I make no assumptions about the total
environment during the middle to late Miocene and so I included all
possible environments (we do not know exactly where these proto hominids
were living but by analogy to animals that exist today and whose
environment we can study, the morphology of the proto hominids would
indicate a forest habitat). Paleoclimatologists and paleobotanists tell
us that between 10 and 5 mya in Africa the environment changed to warmer
dryer conditions. Similar evolutionary changes occured in elephants (we
went from anuncine gomphotheres to true elephants in this period of time)
and many other organisms. Is it not parsimonious to hypothesize that
proto-hominids reacted to simialr changes and evolved?

> Now you've put the grasslands/savannah/steppe and the forest
> together (and presumably are willing to add water like lakes,
> riverine environments and maybe even a sea shore) to creat
> a "mosaic".

Water in necessary for life. Water has to be present in any environment
that a primate lives in since they cannot procure enough water from the
foods they eat. MSS or SSS have never said that water was not present
(savannah does not equal desert), only that the protohominids probably
did not spend an appreciable time in the water (no primates are even
semi-aquatic, even the proboscis monkeys of SE Asia are arboreal in a swamp)

> but in order to create a change of environment/niche you still
> have to have the critters move from their previous niches to the
> new niche whatever it was.

No movement is required if the environment is changing around you. It is
either adapt or die.

> AAS is the
> >scenario that envisions a completely new environment. Which scenario
> >requires the most number of environmental transitions (MSS/SSS has 1)(AAS
> >has at least 2)?
> AAS requires a water environment to the degree that some time
> must have been spent in it or around it. My version does't
> require that it be a sandy beach with no forests nearby or that
> they lived exclusively off fish and shellfish. It could have been
> a swamp with trees around the shore and a sea nearby.

But AAS does presume that they spent enough of their time in the water to
adapt to it. This is the basic premise of AAS. Do not change the target.

> MSS/SSS requires less naturally. AT one simplified extreme it
> requires 1 transition --- forest to grasslands. At the more
> allegedly sophisticated level (i.e. the MSS) then it seems to
> require even less i.e. it may require too few to create a niche
> and for evolutionary laws to operate.

Forest to mixd habitats, hominids probably did not occupy pure grasslands
until at least Homo erectus.

> It's at this point that we can ask the question of why the
> others didn't all become bipedal if there was really no
> change in the environment.

You make the unwaranted assumption that all of the forest had to be
changing into grasslands. For gorillas and chimps to evolve all we need
is some of the forest to remain forest. If the last common ancestor was
living all over central Africa, the ones living in the Congo valley
probably did not need to change because their environment wasn't changing
(jungle yesterday, jungle today, jungle tomorrow (maybe cattle farm
tomorrow), however the ones living in the northern edges of it when the
Miocene environment started to change might have had to adapt to a
different environment.

> We can never know the truth, however, we can apply a
> >simple rule, parsimony (the simplest explanation that fits the
> >observations is the one to be preffered). We may argue about whether or
> >not AAS/MSS/SSS fit the observations (I argue that AAS doesn't fit the
> >observations), but all things being equal, AAS is unparsimonious.
> simple parsimony would work if both produced equally valid
> explanations and this is the view propounded by SSS/MSS. But
> I don't see them equal. There's a pattern among the animals
> that seem to have prediliction/affinity for/with water. I posted
> it separately. This is not a binary/bivalent valued problem and
> if the level of rigor that is expected from AAS is applied to
> the SSS/MSS it too fails. Even more there are other everyday
> pronouncements found in books that start to look flaky i.e.

AAS requires a lengthy stay in water, otherwise no evolutionary changes
would have occured. This is possible, anything is possible, however it
is not parsimonious and we can choose to disagree whether or not AAS are
equally explanatory. Finally, I agree it is not a binary problem, there
is AAS on one hand (and possibly some variation) and a multitude of
different explanations in the terrestrial realm (you could probably get
any ten different paleoanthropologist to give you ten different scenarios)

> 3) Elephants and hippos are allegedly naked because they are large.
> This could be putting things backwards. Marine animals are the
> largest mammals because the water helps them support their weight
> (i.e. whales). So then it must be going into the water that has
> enabled elephants and hippos to get large instead of the reasoning
> that they lost their hair because they became large. How could they
> become large instead of dying off from overheating? They must
> have been using the water to cool off (and as a side effect became
> large and lost their hair). It's strange that hippos, elephants
> and rhinos are hairless AND LARGE. Well, we are large too and
> hairless.

You left some things out, what about sauropods while your at it.
(sauropods were completley terrestrial and hairless)

In your above statement I challange you to demonstrate causality. Is
hairlessness because they are big, big because hairless, big because they
are using water, using water because they are big, hairless because they
are using water, using water because they are hairless? Which 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