Re: Speciation - how do you know?

Gerrit Hanenburg (
Mon, 21 Oct 1996 18:16:31 GMT (Paul Crowley) wrote:

>They could have specialised in a certain kind of shellfish
>eating. Maybe they did scrunch up limpets and cockles in their
>mouths, whereas the gracile forms used crude tools to do the
>same kind of job. This is no more than speculation, but it's
>probably as good as anything you've read so far about A.boisei.

>The robust/gracile split may have paralled the gorilla/chimp
>one. The oceanic littoral would have been difficult, if not
>impossible, for the graciles to exploit as tides would have
>allowed nocturnal predation. Robust forms could possibly have
>coped with the leopards. (This is even more speculative.)
>The robusts might have been driven into extinction once the
>graciles acquired fire and became able to exploit the oceanic
>littoral. (I hope you're no longer dissapointed. ;-)

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

>A lot of evidence can be missed, when you're not looking for
>it. Lucy was found with freshwater crabs, which is along the
>right road.

A freshwater crustacean is not exactly a marine bivalve or shelled
gastropod,let alone a genuine shellmidden. You said:

> > 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.

>Worn teeth in a young adult (say under 25 or 30) indicate an
>unaccustomed diet.

Assuming that the age at maturity in Australopithecines was
ca. 9 years I wouldn't consider an individual of age 25-30 a young
adult but an oldie. In that case tooth wear would fit life history
pattern quite well. (for life history parameters see
McHenry,H.M.(1994),"Behavioral ecological implications of early
hominid body size",Journal of Human Evolution 27:p.84)

>My impression is that the data so far supports my case (although
>I'm first to admit that I've done little research - I have a job
>to hold down). Fossils of infants have been found at Afar which
>is likely to be as close to "coastal" as we'll get. (The Sea of
>Afar probably existed then.)

I'm afraid your impression is not very reliable. Juveniles are also
found at other inland sites (e.g.Laetoli)

>This rule should apply to _all_ hominid fossils; so infant/
>juvenile H.? (H.erectus, H.s.neanderthalis, AMH, etc.) should
>be much more rare than would be expected under the regular
>"inland residence" hypothesis. There should be more than
>enough data to test it now. IOW: 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.

>When some of the answers are in about some of the parasites,
>I believe that we will have a very different picture of human/
>hominid evolution.

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.

>The human gut appears to be designed for a dietery mixture of
>a high-protein food and some fruit. Given the long-standing and
>continuous hominid trend in dentition, it is most unlikely that
>earlier hominids consumed low quality bulky foods.

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