Re: Dissecting the Aquatic Ape: Bipedalism
Paul Crowley (Paul@crowleyp.demon.co.uk)
Sat, 03 Aug 96 21:07:15 GMT
In article <4tsul4$t0f@portal.gmu.edu>
herwin@mason2.gmu.edu "HARRY R. ERWIN" writes:
> : I suggest that a serious re-examination of this "niche" would reduce
> : or eliminate its plausibility. There would definitely have been
> : niches for a larger bodied terrestrial apes or cercopithecoids (the
> : current chimp/baboon) able to climb, feed, hunt and sleep in the
> : trees; there would have been niches for smaller almost entirely
> : arboreal primates. But one in between . . . ?
>
> Dryopithecus laietanus, Sivapithecus indicus,
Niche unknown - in both cases.
> Pongo (and ancestors, which were widely distributed in eastern Asia).
Pongo's niche is high up in the closed canopy.
As I see it: either you have smaller easily climable trees (an
open canopy?) which can provide food and shelter to a primarily
territorial animal OR you have large trees not readily climable
from the ground (closed canopy) where you get pongo, the gibbons,
and many species of monkey. I don't see a niche in between.
The ground-based animals (e.g. proto-baboons or quasi-chimps)
will occupy virtually all the space right up to the closed canopy.
In fact, they may well penetrate it to get to islands of climbable
fruiting trees.
Your purported ape is primarily arboreal but regularly climbs down
one tree and crosses ground to climb up another one. But if there
are ground-based animals in the area they will also be able to
climb up and down such trees. Attempts by the arboreal ape to use
those trees will be defeated, except in temporary "islands" in the
heart of the closed canopy. Attempts by the arboreal ape to become
adjusted to the ground will be defeated by the species that are
already there. It will constantly be driven back into its own niche
in the high canopy. It has no advantages over them, and there are
enormous impediments in the way of any progress towards speciation
into a new ground-based niche.
> This is particularly the case if a significant proportion
> of your preferred food resources are close to the ground, as the thick
> enamel of early hominids suggests.
>
> The dentition of early hominids is consistent with a more ground-based
> diet than that of modern African apes, including a significant proportion
> of rougher food items and less leaves.
This might be a slight change of topic and could be in another
thread, but what you say indicates that early hominids were more
ground-based than chimps, which spend 90% or their time on the
ground. How about 98% for early hominids?
What sort of food do you think it might have been? It has to be
something more attractive than, and superior to, the fruit+nuts+
buds+leaves+honey diet of standard mosaic forest dweller -- or else
the speciation would not have happened. Grubbing for small seeds
is hardly an attractive option.
You can guess my inclinations. Someone should introduce chimps to
shellfish and see how they cope. In addition to using stones they
might also have to use their teeth to open or crush shells, or they
might have to consume many fragmented pieces of shell which could
damage their thin enamel. How do you eat a cockle if you don't
have a pin? The maintenance of thick enamel throughout hominid
evolution indicates the persistence of much the same diet.
Paul.
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