Re: Bipedalism and theorizing... was Re: Morgan and creationists
Paul Crowley (Paul@crowleyp.demon.co.uk)
Thu, 25 Jul 96 22:43:50 GMT
In article <Dv2J9q.FCB@inter.NL.net>
ghanenbu@inter.nl.net "Gerrit Hanenburg" writes:
> Paul Crowley <Paul@crowleyp.demon.co.uk> wrote:
>
> >You'd accept, I'm sure, that early hominids were more ground-based
> >than chimps - which spend (I believe) about 90% of their waking
> >time on the ground. So climbing for a hominid female would be
> >an occasional activity - mainly for collecting fruit.
>
> I wouldn't be so sure about this.Clark and Tobias in their article
> about the Sterkfontein footbones (Stw 573) write:"It is becoming clear
> that Australopithecus was likely not an obligate biped,but rather a
> facultative biped and climber.The exact proportion of its activities
> spent on the ground and in the trees is at present indeterminate."
What do you think they would have said if (assuming that they knew
nothing of real chimps) they'd found a chimpanzee foot? Or a
female/juvenile gorilla foot? My guess is that they'd have said
"Here's a 100% arboreal animal". Bones are only a good guide to
lifestyle or niche if you can compare them with close relatives
whose actual niche is known.
> Your suggestion that chimps posed a serious pressure in the form of
> predation on early hominid populations does not seem very realistic
> since meat forms only a minor component of the diet of chimps.
> Predation by chimps is relatively rare,and if they hunt they prefer
> small mammals (such as Red Colobus).
Predation generates great interest and excitement. AFAIR males get
10% of the diet from it. They would certainly snatch a baby from an
australopithecine female if they found her unprotected by a group.
In spite of the fear inspired in them by modern hss, they have
snatched babies in the Gombe area in recent times.
> Predation pressure by chimps also implies extensive sympatry,which may
> not have been the case.
Sympatry has to be assumed, especially since the recent finding near
Lake Chad.
> You have to think further,i.e.in terms of
> development of the neuromuscular system.
> We have to answer questions like "why does motor-coordination develop
> so much faster in the chimpanzee?","what is the neurological substrate
> (if any) that's responsible for this difference?",etc.
I doubt if we need to go deep here. Hss infants could not possibly
develop any significant predator-avoidance behaviour or other useful
activity in their early years. There is no purpose in having early
development of the neuromuscular system prior to language and some
cognitive awareness. The little that exists is usually dangerous.
(On a ferry last winter I saved the life of a 20 month old that had
just learned to "dash". I caught him as he was about to go through
an open doorway into the black night and a forty foot drop to the sea.
The seaman had just cleared the gangway and had been a bit careless
in removing part of a net barrier as well. That would have been one
more "over-developed" young man who would have left no descendants.)
OTOH, infant chimps need to able to avoid predators (especially
dangerous males of their own species); when quite young they can get
their food; in fact, they can get fruit further out on small branches
that bigger chimps can't reach. If such early development was an
advantage to hss, I'm sure it would be there.
> >Chimp, gorilla, orang and gibbon infants do *not* hold onto hair.
>
> They most certainly do.They grab the hair on the flanks and on the
> sides of the ribcage somewhat below the armpits.
> For a lateral view see the photograph in Goodall's "Through a window"
> where Spindle carries Mel
You've picked a case that makes my point. Why were those bare
patches on Spindle's loins unusual? -- Because he was male.
Goodall relates how exactly the same happened to another young
male, Pax, when he later adopted Mel. You never see bare patches
on females, neither on the loins nor where the infant's hands hold
on. It's probably because female chimps have shorter body hair, or
it may be the different shape of their loins or (unlikely) they may
have tougher skin at those points.
Anyhow, take a good look at the picture of Spindle carrying Mel.
Do you really think that there is the remotest possibility that
Spindle would adopt a bipedal stance while carrying Mel? -- Or
decide to carry him while walking bipedally for a few miles?
Yet that is what you are suggesting early hominid females did.
The picture *might* be conceivable if you think of the infant as
a tiny grasping thing like a Kangaroo's joey, (and, especially,
if you provide a pouch as well) but surely it is out of the
question with a hefty three-year old like Mel?
All other primates use the ventral position and it was, of course,
the ancestral one. At the point of hominid speciation either one
of two things happened: (a) the proto-hominid female did what you
suggest; OR (b) the proto-hominid female first put the child down
and then straightened up her back. Which is most likely?
Paul.
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