Re: Is Oreopithicus the Aquatic Ape Link?

From: rmacfarl (rmacfarl_at_alphalink.com.au)
Date: 02/25/05 

Date: 25 Feb 2005 00:46:57 -0800

Algis Kuliukas wrote:
...
>
> The model I support is that the Pan/Homo/Gorilla ancestor was a
> climbing-wading ape that inhabited wet, swampy woodland. So, way back
> in the Miocene.
>
> > And for how much longer than the chimps?
>
> These apes were the ancestors of both homo and Pan.
>
> > IYO, were the apiths also in this "more water" environment than the
> chimps?
>
> Yes.
>
> > What evidence would you use to support this opinion?
>
> The paleohabitats of A. afarensis (Hadar), for example, were very wet
> and wooded. It was dominated by lakes and other wetlands prone to
> flooding.
>

OK. Serious question here. All the above indicates that your
hypothesis, or is it your model, is predicated on the belief that Homo,
Pan & Gorilla separately evolved from Australopithecus - the latter
paragraph implies that afarensis was, or perhaps predated, the LCA. I
want to address this area of your hypothesis in isolation, which we can
do without the need to consider whether or not water was acting as an
agent of selection in this evolutionary process.

My issue is that when we have addressed this question before, it ought
to have been very clear that there was overwhelming evidence, based on
well-founded evolutionary theory, that this model or scenario cannot be
correct. Specifically, a cladistic analysis of the 3 great ape genera,
australopiths & Homo, strongly refutes the idea that a'piths are
ancestral to P, H & G. It shares many derived characteristics with Homo
that make it clear that bipedal hominids, including australopithecines
& Homo, form a separate clade to other great apes.

I draw your attention to a previous thread where you expressed the
opinion that when looking at a robust a'pith skull, your first thought
was "gorilla". As I recall, Jason immediately took you to task for what
he viewed as a superficial assessment, & proceeded to point out that a
proper analysis showed significant derived characteristics that readily
distinguish robusts from Gorilla. (I've included a diferent, more
recent post of his on the subject of hominid cladistics below.)

In the past, I've also posted a (highly superficial) layperson's
cladistic analysis, which showed, to me, why the suggestion of a
bipedal ancestry for great apes was vanishly unlikely. You have never
produced a satisfactory (to me) refutation of even this analysis.

In light of the above, would you not agree that, as far as this aspect
of your hypothesis, it's clearly been refuted, and it's time you went
back to the drawing board? To be specific, Australopithecines,
including afarensis, most definitely were not ancestral to Pan or
Gorilla, and any hypothesis of human evolution that you postulate
should not include this as a plank...

Ross Macfarlane

<insert>

jae@ucdavis.edu Jan 9, 2005 11:45 am

Newsgroups: sci.anthropology.paleo

...

Hominin generally refers to the tribe (above genus, below family and
subfamily) "Hominini" and includes genus Homo and other bipedal
hominoids thought to be members of a clade to the exclusion of the
African great apes. The term itself isn't meaningful though. What's
meaningful is the relationships.

Cladistics classifies only according to shared-derived characteristics.
Australopithecines share derived traits not seen in extant apes and
thus appear more closely related (i.e. share a more recent common
ancestor) to genus Homo than they are to Pan or Gorilla. These traits
include reduction of the canines, reduction of the I^2-C diastema,
incisiformation of the canines IN ADDITION to the shared
characteristics of the pelvis and hindlimbs. In all cases, it's clear
that extant apes share traits much more like the ancestral condition as
assessed by comparisons within the primates and comparisons to Miocene
fossil apes, all of whom share the greater canine length, larger
diastema, no incisiformation of the canines and none of whom show the
characteristics of a biped. The similarities Australopithecines share
with apes all appear to be sympleisiomorphies or primitive
characteristics (e.g. pronounced prognathism, low basicranial flexion)
which are unreliable traits of absolutely no use in assessing cladistic
relationships. By any realistic cladistic measure, australopithecines
and Homo belong in a clade to the exclusion of Pan and Gorilla.

<end insert>

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