Re: Social evolution of hominids (long)
Paul Crowley (pcrowley@indigo.ie)
Sun, 12 Jan 1997 16:36:46 GMT
ailak@walrus.megabaud.fi wrote:
>1 At the level of the *common ancestor* of all apes and hominids the
>social structure was what the gorillas have today : a very big
>dominant male with his group inhabiting a moderate sized area in
>deep forest.
Since the descendants of this animal are widely spread, it
would seem that deep forests would have had to be extensive
for a long period around that time. That is improbable.
It's more likely that that CA was adapted to more open
territory where males would have had to sleep in trees. So
they would not have been very big and were probably about
chimp size.
>2 The *orang* moved to east,
Orangs do not progress along the ground easily nor do they
go outside forest. So it's unlikely that they "moved east".
>3 The climate turned more arid in Africa, and the local form began
>to cleave.
The claim to a speciation forced by a climatic change is the
first recourse of a bad paleontologist. It's usually proof
of the absence of both thought and evidence.
>4 The ancestor of *chimps* found itself in a less dense forest than
>before. There were more big predators, more cooperation of the males
>was needed, and the order of the male hierarchy had to become less
>steep. The large difference between males and females became a bit
>lesser.
The slightness of dimorphism in chimps has nothing to to
with their social structure. It's a consequence of the fact
that both males and females have to sleep, feed, hunt, fight
and occasionally copulate in relatively small trees where
large size is a disadvantage
>Dolphins have a similar situation. They move freely in the open,
>their females bear big young and nurse them for a long time, so
>the females are permanently receptive and have sex with all males
>of the group to get help from the nearest members when needed.
What evidence is there on dolphins? Have you references?
>Why did our ancestral form become bipedal? Because the female could
>not use her hands for support, when fleeing a presumptive leopard
>with a baby, while the males tried to hinder the cat. She had to rush
>a distance, and bipedally, I think, could be the strategy even
>of a chimp, or am I wrong?
Utterly wrong. Chimps can "gallop" very fast quadrupedally.
The only go bipedal for special reasons, such as display,
and abandon it as soon as they need speed or ease. This
applies especially to a female chimp with an infant holding
onto her belly. With infant attached, she can "gallop" and
climb and fight far more effectively than any equivalent
female hominid ever could.
>The best runners were the mothers of the next generation.
Early hominid females were very small and probably could not
run _at_all_. Even if they could, they were extremely bad
at it. There was NO selection for running capability in
females for the first two million years and probably none
thereafter. Your scenario fits the prevailing paradigm, but
it flies in the face of massive amounts of evidence dating
from since the 1970's.
>The members of a small group of these early prehominids, in an
>evironment where they still had difficulties to get on, desperately
>needed each other. A lone individual would be gone after a few
>nights.
Agreed. We have to focus on how the *group* could function.
>Now we have left the apes and have an early, promiscuous, altruistic
>and bipedal-directed *hominid*. What followed? Not much, for a long,
>long time, in the sense of social evolution.
How many full adult males were in the group? Was warfare
prevalent ? - as in chimps and known hominids (i.e. us).
If so, would a larger group defeat a smaller one? What is
the maximum number of males supportable in a group based on
promiscuous sex? I.e. when does the likelihood of an infant
sharing enough of your genes become so small that its
survival is not worth your taking risks for its protection?
>Life-long
>pairing is largely a cultural trait, for there is no inborn
>mechanism supporting it, similar to the altruistic reflex.
You mustn't be a father -- to say this. Most men care
passionately about their offspring. This is usually quite
adequate to maintain pairing even after the "in-love" phase
has passed. Being in-love consumes a lot of energy and is
necessary only until the first infant(s) start to grow.
>We have
>just 'falling in love', a prolonged remnant from what originally was
>mere mating behaviour, and it is not near that old or it would be
>more long-lasting.
The inborn mechanisms were designed to be *good_enough* for
our paleolithic ancestors. Evolution rarely provides more
mechanisms than are needed. "Fallling in love", the absence
of any contraception, joint parental devotion to offspring,
the harshness of the conditions and the social pressures
within small groups almost certainly meant that monogamy was
the rule. Generally only children with two good parents in
a tightly structured society would prosper. They would then
continue such a "culture". Call it that if you will, but
don't knock it. It works -- or more precisely -- it worked.
It's why we're all here.
It's necessary that the sexes be very attractive to each
other. So it is not surprising that the "cultural"
mechanisms (that enabled the survival of the species) should
break down in a radically different environment. That
breakdown is unlikely to provide good evidence for earlier
social structures.
>How old are the pair-favouring cultures? From before the pair-
>favoring hunter-gatherers radiated? But there are remnants from
>maternal societies around the world, mainly primitive
>agriculturalists, among paternal hunter-gatherers. Did all these
>evolve independently from a preceding promiscuous base? It could
>be so. Then pair-favouring could be a much younger trait than we
>do think.
The concealed estrus and continuous female receptiivity are
unquestionably long-established features of hominid anatomy.
What possible function could they have in promiscuous
groups? It was an evolutionary development. The
development of monogamy is one explanation for it.
What's yours?
There are two fundamental questions: 1) How many mature
males can you have in a promiscuous group? -- I'd say not
much more than a dozen. 2) When did hominids start having
groups larger than this? -- I'd say very early on. Larger
groups would eliminate smaller ones and there would be a
very strong impulse towards language for the management of
larger groups. Such an impulse would be virtually absent in
smaller groups - of chimp size.
Paul.
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