Re: An alternative to ST and AAT

Gerrit Hanenburg (
Fri, 15 Nov 1996 14:32:47 GMT (Paul Crowley) wrote:

>I'm sure that the proto-hominids would have achieved a high degree
>of social co-operation. This implies terrestriality and not a
>rain-forest habitat. So its use would have been new.

The logic escapes me. Why does a high degree of social co-operation
imply terrestriality? How do you know that proto-hominids had a high
degree of social co-operation?
Please can we have an answer that goes beyond mere speculation?
You often say "I'm sure that...." while your certainty has no
empirical ground whatsoever and as such has as much scientific value
as a religious belief.

>> Lucy's climbing abilities don't need a new explanation because it's
>> what she inherited from her ape ancestors. Only what's new needs an
>> explanation,i.e. bipedalism.

>This thinking is not clear. The whole ecology and niche have to be
>explained. Why did the bipedalism retain these strange climbing
>adaptations? (If that is what they were.)

Why strange? Is it strange that chimpanzees combine quadrupedalism
with arboreal adaptations? Apparently,in your mind there is only one
possible evolutionary path to bipedalism,and everything that deviates
from it is considered strange.

>If the LCA had been a quasi-chimp, then it would have had short legs and long arms for
>its quadrupedal gait; bipedalism should have shortened the arms
>almost immediately, and lengthened the legs, as we see with

Unless the long arms and short legs still were usefull in some other
(arboreal) context.

>I can't see how H.erectus would be much worse than Lucy
>at climbing ordinary trees; and it would be far better at running
>and walking.

The latter is probably true but the former isn't.
The climbing abilities of H.erectus would probably have been similar
to modern humans since the postcranial anatomy of the Turkana Boy
shows it to be very similar to modern humans. Lucy's postcranial
anatomy is different,the proportions are more apelike and suggest she
was a better climber (though probably not as good as a modern chimp).

>Your wide generalities give no indication of the kind of life you
>think Lucy must have lived.

I picture Lucy in many different scenarios (sometimes she is caught by
a feline during feeding,sometimes it is scared off by a coalition of
screaming males swaying branches) but,no matter how detailed I make
her life,at the moment there is not enough data to unambiguously
eliminate all possibilities but one.
If only I had a time machine,.....but all I have is small fossilized
window with a distorted view on the past and some extant (probably
inappropriate) comparative material.

>An ability to run is often a life-saver as is an ability to cover, say,15 miles in a day instead of
>10. What is this extra "degree of arboreality" and how did it
>justify the 2 Myr delay in acquiring those substantial advantages?

Why do you persistently insist on this detail when there are no means
to assess it? What does it help you if I conjecture that she spend 15%
of her daily feeding time in the trees? How are you going to falsify
Chimpanzees,after several million years still aren't very good
quadrupeds. What keeps *them* from becoming so if efficient
quadrupedalism is such an advantage?

>What could Lucy do that H.erectus couldn't?

Let's try to answer the question with comparative material.
What can a chimp do (better) that a modern human can't?
But maybe we should ask the question the other way around.
What could H.erectus do that Lucy couldn't? After all H.erectus is the
derived creature. What factors favor efficient long distance travel,a
long linear body build,and a big brain?

>I know little about this, but a diet high in fat does not strike
>me as being as healthy as one high in protein.
>Our primate ancestors "who's digestive system and metabolism are mainly adapted
>to frugivory/folivory" must have consumed very little animal fat.
>Adaptation to a very-high-fat diet sounds more difficult.

Primates can deal very well with fat (many nuts and seeds have a high
fat content). High protein levels on the other hand poses problems in
the form of increasing levels of toxic metabolic wastes,greater
metabolic costs (due to the fact that protein metabolism is less
efficient than that of fat and carbohydrates),dehydration,
micronutrient deficiencies,etc.

>The "principle of competitive exclusion" is absolutely fundamental.
>If vervet monkeys had no edge over savanna baboons, they would
>rapidly be driven into extinction - and vice versa. I am utterly
>mystified by a failure to appeciate the universality of this

Then please tell me in all detail what this edge is that Vervet
monkeys are supposed to have over Savanna baboons.
If you can't do it for two extant species of primates how much more
difficult will it be for an extinct species.
I don't deny the importance of interspecific competition in shaping an
ecological community but within a community it is not simply a linear
proces between species A and B,but a network between species
A,B,C,D,etc. How species A and B interact may depend on how species B
and C interact,and this in its turn may depend on the interaction
between A and C.
The outcome of competition between A and B may be quite clearcut in
isolation (put vervet monkeys and baboons in the same cage,and the
vervets will be dead in a short time) in a real ecological community
many more factors influence the outcome.
I'm utterly mystified by your failure to appreciate the complexity of
ecological systems.

>> I simply do not favor one monolithic hypothesis.

>Bipedalism needs at least one very good hypothesis (two or three
>very good ones might be better, but one will do for a start ;)

There are the hypotheses of the origin of bipedalism as a feeding
adaptation. See for example Hunt,K.D.(1994),The evolution of human
bipedality:ecology and functional morphology. Journal of Human
Evolution 26:183-202.

Then there are the ones that emphasize physiology. See for example
Wheeler,P.E.(1984),The evolution of bipedality and the loss of
functional body hair in hominids. JHE 13:91-98. (several more papers
have been published by Wheeler between 1984 and 1996 in which he
elaborates the hypothesis in great detail)

Bipedalism as a social adaptation.
See Jablonski,N.G.and Chaplin,G.(1993),Origin of habitual terrestrial
bipedalism in the ancestor of the Hominidae. JHE 24:259-280.

These are only some examples.
Reading some of these papers might prevent you from making
stereotypical remarks like "all professional paleoanthropologists are
the same" and free you from the idea that they never tell anything.
Before you criticize an entire scientific discipline you should study
the ideas that circulate within it,preferably as they are exposed in
the primary literature (the relevant journals are available in the
university library). If you refuse to do that,we don't have to take
your criticism seriously.