Re: An alternative to ST and AAT
Gerrit Hanenburg (G.Hanenburg@inter.nl.net)
Sun, 17 Nov 1996 11:30:14 GMT
Paul@crowleyp.demon.co.uk (Paul Crowley) wrote:
>The logic is simple. A high degree of social co-operation implies
>terrestriality because we observe that arboreal apes are not co-
>operative; they do not need to be as they have no predators
>(other than H.s.s.).
The fact that arboreal apes (I assume you mean Gibbons and Orang utan)
are not co-operative does not imply that co-operative species are
terrestrial. The conclusion that co-operation implies terrestriality
because arboreal apes are not co-operative is invalid.
Apart from that,Gibbons do co-operate in territorial defense.
>Why not try to make out an alternative case? We can only try
>to draw conclusions from the evidence we have. I think we have
>more than enough.
>Susan's point: "Afarensis' sexual dimorphism suggests a high degree
>of competition among the males for access to females" is IMO no
>more than a weak suggestion drawn from a very general mammalian
>rule. The dimorphism could have had many other origins.
Possibly,but it is an empirical finding that sexual dimorphism in
extant primate species is associated with sex related competition. The
"very general mammalian rule" is a better basis for deduction than any
Thus McHenry's suggestion that "Perhaps the apparent fact that
A.afarensis had higher sexual dimorphism than Pan indicates that the
species had a recent ancestor with a social system in which males were
more solitary" is reasonable and your assumption that protohominids
were like chimps in their social structure may not be true.
(McHenry,H.M.(1991),Sexual dimorphism in Australopithecus afarensis,
J.of Human Evol.20:21-32)
>Any discipline that accepts vague generalities as answers is in a
>bad way. I'm suggesting that as soon as you try to fill out your
>hypothesis with any detail, you will see that it does not work.
>So I would ask you how such a 15% time could have yielded enough
>benefits to compensate Lucy for the costs of reduced bipedal
>capacity, by comparison with a female H.erectus. I would ask you
>to describe how each of them coped with their small infants and
>other young during such activity. Increasing the period to 30%
>or 45% makes it worse. I cannot see Lucy's morphology providing
>any significant advantages at all in this context.
"reduced bipedal capacity" is a bad expression for Lucy's
condition,because it suggests that her ancestor was a better
bipedalist. It also suggests that there is somekind of ideal to be
achieved. Once more,Lucy's anatomy is a compromise just like that of
chimps,only with optimization shifted towards bipedalism. Such an
anatomy is an advantage if a considerable amount of nutritious biomass
is still located in trees or if trees still profide a refuge.
We have already discussed how Australopithecines could have carried
their infants. It's no use going over that again because you don't
accept it as possible anyway.
>Explanations of "edges" of the Vervet/Baboon nature usually require
>no more than a minimum of investigation. Delving into complexities
>of interactions is rarely needed when outlining the niche of a
>medium to large-size mammal.
You should know,since you have a lot of experience in that direction.
>Thanks for the references. I'm familiar with most of them.
You mean you've read them? (I don't think so)
>But, surely you agree that, in spite of their thoroughness and
>apparent scholarship, they are all almost embarrassingly bad?
They're better than anything you have proposed.
>This can be seen by assuming one is right and asking where that
>would leave the others. Why are they so bad? The answer has to
>be that one or more of the basic, but unquestionable, assumptions
>is wrong. I suggest that one is the "savannah hypothesis" or as
>Phil Nichols would say: "the _fact_ that our ancestors lived on
The assumption that hominids lived in a savannah (sensu lato)
environment is at least based on fossil evidence,something that can
not be said of the littoral ape theory. The littoral ape theory is
solely based on speculation.
Gerrit (who will refrain from further participation in this endless