Re: Neandertal skull features

Dave Oldridge (
Mon, 28 Aug 1995 13:35:55 -0300

In article <41ptmt$>, (Phil Nicholls) wrote:
> (Jim Foley) wrote:

> >I have a book which claims that the Neandertal facial morphology could
> >be caused by environmental effects, rather than being genetic in origin.
> >As support, it quotes the following paragraphs from Klein's "The Human
> >Career":
> > The full functional interpretation of Neanderthal facial structure is a
> > matter of ongoing debate, but there are some points of broad agreement.
> > The forward placement of Neanderthal jaws and the large size of the
> > incisors probably reflect habitual use of the anterior dentition as a
> > tool, perhaps mostly as a clamp or vise. Such para- or nonmasticatory
> > use for gripping is implied by the high frequency of enamel chipping and
> > microfractures on Neanderthal incisors, by nondietary microscopic
> > striations on incisor crowns, and by the peculiar, rounded wear seen on
> > the incisors of elderly individuals. Similar, though less extensive
> > damage occurs on the teeth of Eskimos, who also tend to use their
> > anterior jaws extensively as clamps.
> > Biomechanically, the forces exerted by persistent, habitual,
> > nonmasticatory use of the front teeth (= "massive anterior dental
> > loading") could account in whole or in part for such well-known
> > Neanderthal features as the long face, the well-developed supraorbital
> > torus, and even the long, low shape of the cranium. Massive anterior
> > dental loading could further explain the unique Neanderthal
> > occipito-mastoid region which perhaps provided the insertions for
> > muscles that stabilized the mandible and head during dental clamping.
> >Now, I would have interpreted that to mean that Neandertals evolved
> >facial features to handle the stresses of using teeth and jaws for
> >non-eating purposes. But Klein's wording is vague enough (especially in
> >the first sentence, second paragraph) that I can't rule out the
> >alternative explanation that dental loading could directly cause these
> >facial features in an individual with no genetic predisposition towards
> >them.
> >What is Klein saying here? And what do others think?
> >--
> >Jim (Chris) Foley,
> >Assoc. Prof. of Omphalic Envy Research interest:
> >Department of Anthropology Primitive hominids
> >University of Ediacara (Australopithecus creationistii)
> I think that very often evolutionary explanations are phrased in print
> in such a way that they have a Lamarkian sound to them. As I read the
> passage from Klein that is what I see. Klein is outlining a
> hypothesis put forward a few years ago by Yoel Rak. That's all.

If the claim is that actually using the facial muscles in this manner
somehow causes the bones to grow in a certain way, that should be
capable of independent investigation. But the selection pressures that
would SELECT for that particular bone structure genetically would have
to operate over a fair length of time, I would think.

In other words, if it was strictly an environmental thing to do with
using teeth for non-masticating purposes, it was basically social and
only affected individuals, but then social traits often get tied up with
sexual selection. Gaaak---it's just hard to sort some of these things
out :-)

> Phil (Chris) Nicholls []
> Institute for Hydrohominoid Studies
> University of Ediacara
> Semper Alouatta!

Dave Oldridge