Re: An alternative to ST and AAT
Paul Crowley (Paul@crowleyp.demon.co.uk)
Thu, 14 Nov 96 22:16:13 GMT
In article <56cvm2$8ae@news.NL.net>
G.Hanenburg@inter.nl.net "Gerrit Hanenburg" writes:
> But the rainforest was exactly the kind of biome that was disappearing
> in late Miocene/early Pliocene eastern Africa. In its place came a
> diverse mosaic of forested and more open country with increased
> seasonality.
I'm only looking for a small area of rain forest - on the slopes
of a ridge of some high mountains.
> Why would an ape change its anatomy in the direction of Lucy's design
> when staying in its original habitat?
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.
> In the rainforest there was no need for bipedalism and it
> already had the design of a skilled climber.
I agree that the habitat has to involve more than the rainforest;
I see it (or the palm trees) providing only part of the diet; and
its use certainly wasn't the reason for bipedalism. I'm looking at
it primarily as the reason for the _restraint_ on the development
of a more effective bipedalism.
> 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.) 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
H.erectus. 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 reason was that A.afarensis didn't
> have to be as efficient as H.erectus because it didn't have to cover
> the same long distances and because its bipedality had to be
> compatible with a certain degree of arboreality.
Your wide generalities give no indication of the kind of life you
think Lucy must have lived. 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?
What could Lucy do that H.erectus couldn't?
> Which means the littoral ape needed a more or less continues access to
> fresh water.Could be a problem in a littoral environment.
That our ancestors needed a more or less continuous access to fresh
water is hardly deniable. (Does anyone deny it?) One of the best
places to be sure of it is at the bottom of a long ridge of high
mountains; about the worst is a high, arid plateau.
> >There is no reason why the Australopithecines could not have
> >adapted to a diet with a somewhat higher protein content.
>
> We are talking about primates here who's digestive system and
> metabolism are mainly adapted to frugivory/folivory.
Those primates did digest meat. Selection towards an increased
proportion of protein in the diet would hardly be a major problem.
> Contrary to shellfish the meat of artic verbrates has a high fat
> content which results in a high caloric value. Eskimos do not have to
> rely on protein for their energy and can subsist on animal matter
> alone during winter. Protein content does not exceed 30% of total
> calories.
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.
> Apparently I have a somewhat different view on community ecology than
> you. If I look at todays wildlife communities in Africa I see numerous
> sympatric species of bovids,large carnivores,monkeys,birds,etc. I
> wonder how they all manage to have a particular "edge" over the
> others. What "edge" do you think Vervet monkeys have over Savanna
> baboons,Ruppell's Griffon vulture over White-backed vulture,and
> Grant's gazelle over Thomson's gazelle?
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
principle.
> 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 ;)
Paul.
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