Re: Absence of Canines in Apiths


"JAE" <jae@xxxxxxxxxxx> wrote

<snip>

Give it up, Jason. You're not fooling anybody worth fooling. In the future
might I suggest that if you want to pretend that you haven't read something
that you state this BEFORE you reveal that you've already read it.

So, Jason, did you see the post entitled: Novel technique offers new look at
ancient diet dogma? What do you think of this microwear evidence? Kind of
interesting how it seems to confirms the monsoon climate of my scenario.
What do you think of Ungar's interpretation/conclusion? Did you catch on to
what he was saying? Let me tell you what I saw and you tell me if you think
I'm on target. First I'll post the pertinent passages from that article:

*** begin cut and paste ***

http://live.psu.edu/story/12922

Australopithecus africanus, which lived between 3.3 million and 2.3 million
years ago, and Paranthropus robustus, which lived between 2 million and 1.5
million years ago

pits and scratches found on the teeth offer a visual history of the type of
food
consumed by the tooth's owner. Pits indicate a diet of hard, brittle foods,
like nuts and seeds, while scratches imply a diet of tough foods, like
leaves and possibly meat.

The analysis showed that the two species had significant amounts of overlap
in their diets and that while P. robustus had more complexity in its tooth
wear, indicating that it ate more hard and brittle foods than A. africanus,
it ate tough foods as well.

The researchers believe that this indicates that the species frequently ate
the same types of foods, but that in times of scarcity or seasonal changes,
P. robustus changed its diet to include foods that differed from those of A.
africanus.

"The difference in their evolution in terms of diet is not driven by their
preferences, but by scarcity," Ungar said. "It gives you a whole new way of
thinking about dietary adaptation."

*** end cut and paste ***

I think the following comment was especially pertinent: "The difference in
their evolution in terms of diet is not driven by their
preferences, but by scarcity." What do you think he meant by that comment?
To me it suggests that P. Robustus experienced longer and more intense dry
seasons than did A. Africanus. Do you agree with this interpretation? Do
you think Ungar's interpretation/conclusion tends to confirm the monsoon
climate (wet season, dry season) of my hypothesis? In the least you have to
admit that it does seem kinda funny how my hypothesis seems to have
anticipated these interpretations/conclusions?

And then there's another issue that has to do with what I described as
Reversal in climate at 3.5 mya. Note that Australopithecus africanus, which
lived between 3.3 million and 2.3 million years ago. This is considered a
wetter (a period of shorter dry seasons) than Paranthropus robustus, which
lived between 2 million and 1.5 million years ago (a period of longer dry
seasons).

What do you think of my criticism of Tim White's interpretations/conclusions
that I expressed a couple of months ago?

*** begin cut and paste ***

http://makeashorterlink.com/?P2971114C

Newsgroups: sci.anthropology.paleo
From: "Jim McGinn" <jimmcg...@xxxxxxxxx>
Date: 5 Oct 2005 10:27:07 -0700
Local: Wed, Oct 5 2005 9:27 am
Subject: Reversal in climate at 3.5 mya

>>From an interview with Tim White:
> Interviewer: How is our view of early hominid evolution changing?


> Tim White: <snip> We've also
> learned that the idea that the last common ancestor of
> hominids was like a chimpanzee is just wrong. The more
> closely we approach that last commonancestor with real
> fossils, we're learning that its browridge is shaped
> differently from any chimpanzee's, and its canine teeth
> are much smaller. Chimpanzee incisor teeth are very
> broad, and they use them for eating fruits. We don't see
> that in any of the oldest hominids. This is saying that
> chimpanzees evolved that specialization after the split
> with our ancestors.


I think Tim is being mislead by the evidence. This
is because there was a reversal in the climate from
about 3.5 mya and 2.5 mya. IOW, the dry season was
very pronounced from 8.1 mya to 3.5 mya, then the
climate became wetter (dry season shorter) from 3.5
to 2.5 mya, then it became more pronounced again at
2.5 and got very pronounced more recently. The
fossil (lucy) that Tim found was in that wetter
period, 3.2 mya. Lucy's teeth indicate she was
eating softer leafy foods than the hominids that
preceded. So the fact that chimpanzee incisor teeth
are more similar to Lucy's incisor teeth than to
Sahalanthropus gives us no reason to assume that
chimpanzees evolved that specialization after the
split with our ancestors. (This, of course, is
complicated by the fact that chimpanzee fossils are
so rare.) So, when the effects of the reversal in
climate at 3.5 to 2.5 mya is properly considered
there is no reason to assume that the LCA was not a
chimp or an animal very similar to a chimp.

Jim

*** end cut and paste ***

Do you think this microwear evidence tends to confirm or dispute my critism
of Tim White? What do you think they'd find if they applied the same
microwear examination techniques to the Sahalanthropus tooth specimens? I
predict that they would look more like Robustus than Africanus. (Why?
Because the dry season of Sahelanthropus was more similar to that of R than
to that of A.) What do you think?

Don't worry, Jason. I'm not actually expecting you to answer any of these
questions. Think of them as rhetorical. Go ahead and insert the typical
Verhaegen style robopost about how you refuse to consider anything that . .
.. blah, blah, blah--as if anybody cares.

Jim


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