Re: Missing Link (was Human Chimp Gorilla)
Mike Muller (muller@flmhh.ufl.edu)
Sun, 21 Jul 1996 14:57:34 -0400
Stanley Friesen wrote:
>
> Mike Muller <muller@flmhh.ufl.edu> wrote:
> >Homo erectus, as defined by the holotype, only exsisted in Asia. The
> >African material has been lumped into the erectus group. But there are
> >MANY morphological differences show it to be quite different.
>
> I think I have to disagree with this - if understand it correctly.
>
> Except for the earliest African specimens, most of the African H.
> erectus is only subtly different from Asian H. erectus. I base this
> statement on the detailed morphometric analyes in _The Evolution of
> Homo erectus_ by G. Philip Rightmire.
>
> See, for instance, Fig 37 in that book, which includes in the caption
> the following statement: "Olduvai Hominid 9 departs from the
> Zhoukoudian pattern in torus thickness but not in other measurements".
>
> And in Fig. 38 the Sangiran (Java) specimens depart more from the
> Zhoukoudian (China) specimens than do the Olduvai ones. And Fig, 35
> shows more variation in the Javanese specimens (Sangiran versus
> Ngandong) then between Sangiran and the Oldvuai series - again mainky
> in the torus thickness.
>
> Only the KNM-ER series (3733, 3883 and so on) along with KNM-WT 15000
> differ enough from the Asian specimens to be even worth subspecific
> recognition. The Olduvai specimens fall close to either the Sangiran
> or the Zhoukoudian specimens in all cited measurements. And the later
> Javan specimens (Ngandong) differ from all of the others in having a
> significantly larger cranial capacity.
These examples are not dealing with the morphocharacters possess by the
classic erectus holotype of keeling, TMJ shape, torus shape and position
of brain, and occipital characteristics. Which the African material does
not possess.
> I suspect that African H. erectus came *from* Asia. That is I believe
> that H. erectus evolved IN Asia and then immigrated to Africa. The
> populations that left African would have been aprt of the Homo habilis
> complex (perhaps the form sometimes called Homo rudolphensis).
>
> How can this be? Simple - new species tend to arise in small
> peripheral populations that have become isolated in habtitats that
> differ somewhat from the ancestral habitat. Under these conditions
> (small populations, high genetic drift, directional selection)
> morphological change can be amazingly rapid. In fossil contexts this
> is called "Punctuated Equilibrium".
I think tht Gould would take exception to that definition!
> Simply put, I would guess that the origin of Homo erectus was a
> punctuation event - a rapid evolutionary transition, taking probaly no
> more than 25,000 years (1,000 generations). Note, this is rather less
> than the *uncertainties* in the dates of the earliest Asian H.
> erectus!! This means that the appearance of H. erectus would be
> virtually instantaneous, fossil-wise.
The newest Ar/Ar dating of Asian materials is not uncertain and giving
sound dates for classic erectus from 1.8 on the Mojokertoand the
thermoluminescence dating is providing dates to much less than 100,000
for the Ngandong materials.
> If I accepted H. ergaster I would restrict it to the Turkana basin
> specimens. The Olduvai and later North African specimens fall well
> within the range of Javanese H. erectus.
The only speciment that falls into the classic erectus character suite is
OH9 the others only exhibit vague features. The supraorbital torus is a
good example and one cited to place the African material into H.
erectus...yet they are very different, also the anterior position of the
brain in the asian material is more anterior as a result. African torus
is linear and the Asian is arching, the tempromandibular joints are
different dimensionally and there is absolutely no keeling present and no
occipital torus present on the African material. The presence of the
keeling and the occipital torus are classic characters from the Homo
erectus holotype how can it be justified to place material withing the
hypodigm if it does not possess these two major diagnostic characters...
and please don't repeat the tired, old range of variation argument it
just doesn't hold here. The variation is too radical.
I will look at Rightmire if you look at work by Bernard Wood, and then
we'll have another go here, okay?
Holly Reeser Florida Museun of Natural History.
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