Re: AAT Questions...

21 Jul 1995 06:21:01 GMT

Ralph L Holloway ( sez:
`I don't think limb ratios by themselves are going to convince the AAH
`doubters, whatever they might be in A. ramidus. I will let Jim Moore
`answer your criticism, but when we speak of evidence, I think most of us
`mean something really striking about the morphology of the bones
`themselves, in particular, their shape, and what they can "tell" us about
`muscle attachments, etc. I am afraid that most of us doubters expect aquatic
`morphological adaptations to hopefully include flippers. I for one would
`be willing to reexamine my biases if hominids could be shown to have had
`flippers...;-), or have I missed something... Seriously, AAH suggests
`about 3-4 MY of aquatic adaptation, and that should something truly
`aquatic R. Holloway.

As I said, I don't know of anything that would clearly and specifically
reinforce the AAH, but wouldn't you say that a semi-arboreal intermediate,
say with gripping feet, very long arms, bow legged, at 4.4Mya would go a
long way toward killing the AAH?

I could speculate about other features that might be beneficial to
an aquatic ape, but none that I could bring a case for as being

..If I were an aquatic ape, I'd want to be born with a built-in
snorkel...other than that I'm pretty happy about how I function
in the water. Resting on the surface, my face points downward
so I can watch the activity on the bottom. If I take a breath,
I can pop down 20ft, putter around for a minute or two,
chasing the fishes, bluffing with the crabs, then bob back to
the surface, catch my breath, relax for a while, then repeat.
I can happily keep this up for hours in the summer, and note
that the water in the Gulf of Georgia is not exactly tropical.

`Flippers' would be useful, but would they leave any
skeletal evidence? Remember this is an animal that hasn't wholly
abandoned the land, so their should be a heel on the rear limb,
but no need for an opposable first toe. Rather like our own feet.
Perhaps more able than us to rotate to pointing straight downward,
like a ballerina on point. Would that be detectable in the bones?
Perhaps the toes, while fairly uniform in size, would be longer
than ours. This is something we would have to lose rapidly once
we took to walking exclusively.

Narrower shoulders would also be useful for streamlining, though
that need has to compete with the need for lung capacity for
diving, and strong front limbs for swimming. I don't know what
sort of synthesis these requirements might result in.

It seems to me that a problem with this line of speculation is
that the whole point of the AAH is that our present structure
is the residue of an aquatic past. It doesn't require us to
have acquired some features there and then shed them, but rather
to have found them useful and retained them. Like I said,
what the post aquatic ape _wouldn't_ have, would be strong
residual arboreal adaptations. We could expect fossil evidence
of the _end_ of the missing period to be more effective at
ruling out the AAH than substantiating it. On the other hand,
if we found evidence of a rapid development of hominid bipedalism
toward the _beginning_ of the missing period, especially if
it occured in a region of shoreline habitat, it might be
considered to at least put the AAH in a more favourable light.

..Speaking of `missing periods', do we even have a firm candidate
for a common ancestor of the hominid (if not pongid) line
prior to 8 or 9 Mya ? I learned a bunch of names of miocene
apes way back in school, but I wonder now how they're placed,
have they all been edited off the human ancestral line, like
poor old homo sapiens neandertalensis?

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