Re: Speciation - how do you know?

Paul Crowley (
Thu, 24 Oct 96 10:48:12 GMT

In article <54geq2$> "Gerrit Hanenburg" writes:

> Phew!
> Minor questions remain unanswered of course but once again the
> littoral ape theory has shown its great explanatory power. ;-)

Can I take it that you are now converted to the cause?

> > > a) shellfish remains will be found with hominid fossils to
> > > the extent that will show they formed part of the diet
> > > throughout hominid existence;
> So,the least I expect is an accumulation of shellfish remains with
> some indication of the remains having been manipulated.

I live near the sea now, but for most of the last 5 Myr it would
have been 200-300 miles away from here, so I would not expect to
find much in the way of pliocene marine shellfish; similarly for
most hominid sites. It is only on geologically raised formerly
coastal sites that good data is likely to be found; and these
are rare.

Shellfish middens are only likely to be found in connection with
complex and well-organized societies, where food is collected at
some locations and comsumed at others. Again it is only the
larger species of shellfish that are likely to be treated in this
way and again only they would retain their identity in the middens.

A diet of small gastropods would leave direct fossil evidence,
whether it was crunched up by stones or in the mouths of Robusts.
So it's probable that middens represent only an extremely small
fraction of hominid shellfish diet, and then only at later stages.

> >Is the adult/juvenile/infant
> >ratio in the hominid fossil record similar to that for, say,
> >elephants, pigs, or crocodiles? Or is it distorted towards
> >adults and towards adult males in particular?
> Don't count on a research grant.

A few hours in a library should be enough.

> At the moment I don't see how present parasite-host relationships can
> tell you much about the ecological and social circumstances of
> hominids in the distant past.

Parasites and hosts co-evolve. The current ecology of the
parasite and its close relatives and its DNA can tell you much the
evolutionary ecology of the host. When there are many parasites,
the information from each would be cumulative.

> The potbelliedness of Australopithecines,as inferred from the
> cone-shaped thorax and the wide flaring iliac blades,might indicate
> quite some length of gut. Long guts are generally not associated with
> easy digestability.

It is somewhat far-fetched to make conclusions about gut dimensions
and structure from general abdominal shape. It would follow from
your argument that the main hominid line changed its diet drastically
at some later point. There is no indication of this anywhere.

> The masticatory apparatus of robust Australopithecines,with emphasis
> on heavy chewing would be quite compatible with this.

On the contrary, you can't take the jaws and teeth of one species
and the thorax of another and come to valid conclusions about the
diet of one (or both).

The teeth of the Robusts are most unusual and highly informative,
but I suggest that the size of the jaw and of the masseter muscle
could have origins other than "heavy chewing". The inference is
too facile and (as with much in PA) a more sceptical attitude should
be adopted. AFAIK male gorillas do not do a lot of "heavy chewing".
Their massive jaws need another explanation; it may be for defence
against predators.