Re: Speciation - how do you know?

Gerrit Hanenburg (
Sun, 20 Oct 1996 14:47:56 GMT (Paul Crowley) wrote:

>A theory does not have to explain everything, especially in
>biological fields. A.boisei is so exceptional, that it may be
>a long time before anyone has the beginnings of an explanation.

This is somewhat disappointing. Here we have a theory that explains
almost every aspect of human evolution but fails to account for a
major change in morphology in one of the most important functional
complexes;the masticatory apparatus of the robust Australopithecines.
While this theory maintains that shellfish was the main component of
the hominid diet from A.afarensis (A.anamensis?) to H.sapiens we see
something remarkable happen in the robust Autralopithecines such as
A.boisei. In relation to A.afarensis:a strong reduction of facial
prognathism,almost a doubling of postcanine tooth area,diminution of
anterior teeth,hyper thick enamel,massive jaws,large anterior
projecting zygomatic arch indicating a strongly developed masseter
muscle,etc. In short,we see a masticatory apparatus that
biomechanically relates to heavy chewing.
Did you ever eat oysters,Paul?

>The littoral ape theory has many explicit and implicit tests or
>forecasts, such as:
> 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 far zippo,except for the latest stages.

> b) fossil hominids found on inland sites will show a strong
> bias towards the early adult age range with indications
> of early death resulting from excessive tooth wear
> caused by unaccustomed diet;

This is simply an ad hoc "prediction" based on a personal
interpretation of data you already know. How does one distinguish
tooth wear caused by an unaccustomed diet from wear caused by normal

> c) fossil hominids found in sites further from the coast will
> show a smaller proportion of pre-adults.

Compared to the ones found in coastal sites? :-)
Anyhow this requires a statistical analysis which may not be very
reliable at the moment due to very small samples.
Something for the far future when we have discovered numerous coastal

> d) the initial adaptation to bipedalism will be shown to be
> early and fast;

That doesn't distinguish it from other theories,in particular the ones
that are based on a punctuated equilibrium model.

> e) fossils of infants and young will show fully bipedal feet
> -- without an ability to grasp; these will long pre-date
> any significant expansion in brain size;

Though Stw 573 is an adult,this hominid fossil indicates that a
grasping ability was still present at ca. 3.5 mya.

> f) adaptations for an arboreal existence will be shown to be
> lost quickly;

This point we have discussed at length. According to several PAs
A.afarensis had arboreal adaptations up to at least 3mya.

> g) early hominid fossils will not be found at any significant
> distance away from large bodies of standing water;

All early hominids are found in association with non-marine deposits.

> h) the theory maintains that soft-body adaptations occurred
> early; early hominid fossils may show indications of
> subcutaneous fat, especially in females; nakedness and
> sweating might also possibly be indicated;

The value of this prediction is practically zero due to the fact that
information about these soft tissues is extremely rare in the fossil

> i) studies of the DNA of human water-borne and water-reliant
> parasites will tend to show a very long evolution,
> indicating the long existence of large, localised,
> resident hominid populations;

Which water-borne and water-reliant parasites are you refering to?
And how does their DNA give any information about their past
association with hominids?

> j) no significant evidence of hunting will be found before
> about 200 kya.

I leave this one to the archeologists,but cutmarks on animal bones
seem to indicate that meat was on the diet before that time,whether it
was acquired through systematic or opportunistic hunting or

>Expense can be seen in many ways. Blood supply is good, but not
>the only one. The cost of the change may be high. The Hss 20%
>reduction in the last 20 kya has resulted in a lot of impacted
>wisdom teeth, so the loss in size must have had significant
>benefits - namely, a reduction in cost. Again the speed of
>change in a new niche is an indication. The loss of large
>canines occured quickly in early hominids. Presumably they did
>not need them, so they lost them fast; so they must have been

Non sequitur.
There is another possibilty. The canine may have acquired a new
function in hominids. Functionally it became an incisor. As such its
function may have been improved upon by bringing it in line with the
other incisors (i.e. closing the diastema) and reducing the hight of
the crown to the level of the occlusal plane.

>Also, observation of living primates and other mammals
>can tell us that an organ is expensive. When a canine goes, the
>animal often dies soon after. Those individuals that keep the
>best canines predominate and have more offspring. It's a
>perpetual weapon race.

That doesn't tell you that an organ is expensive,but only that it pays
to have the organ.

>> Thick enamel may very well be a response to an abrasive diet,but a
>> diet can be abrasive in different ways.

>So early, mid and late hominids had an abrasive diet. An abrasive
>diet of what?

Not necessarily all three categories.
Several possiblities come to mind:vegetation with a high silica
content,those parts of plants whose consumption may include some of
the surrounding matrix (roots and tubers),hard fruits and nuts.
And also less abrasive,low quality material that is consumed in bulk.

>> Crushing shellfish is only one of them. (and unlikely in the case
>of primates)

>Since late hominids had a diet of shellfish ("coincidentally"
>abrasive) and were, in fact, primates, the "unlikeliness" goes
>out the window.

We only know of Homo sapiens that shellfish are and were part of the