Re: [Marxism] human origins

[Paul <pgallagher4@xxxxxxxxxx>]

Charles Brown wrote:

> Paul Gallagher:
>
> It's worth emphasizing that a history of life largely determined by
> catastrophic changes in the physical environment is very different from the
> traditional view where natural selection is primarily the result of
> individuals competing within their species for scarce resources.
>
> ^^^^^^
> CB: I could see competing "within a species" for scarce resources as giviing
> rise to new traits, but doesn't the Mayr hypothesis contemplate that
> speciation occurs more often when populations of the same species are
> physically separated, and therefore _not_ in direct competition with each
> other for scarce resources or otherwise ?
Yes, in Mayr's theory, speciation is non-adaptive. It is not the result
of selection for
reproductive isolation. Instead it is a result of geographic isolation.


> They are in different places and
> not interacting enough to mate. How would they interact enough to compete ?
> Wouldn't it be competition between close , but different species, within
> close niches, like between homo sapiens and homo neanderthalis ?
Once speciation has occurred, the new species might spread back into the
parent species'
range. However, typically closely related species can't coexist, since
they have very similar
needs, and one species will out compete the other.

I think it's fair to say that later neo-Darwinist authors emphasized the
role of intraspecific competition
(within the species), as opposed to competition among species, as causes
of selection. There
are in particular many times where authors equate selection with
competition, forgetting the many
other ecological processes, such as predation, disease, mutualism and
cooperation, as well
as the role of physical environment.

> But another point. When I studied the history of natural historical science,
> there was , of course, the creationist school ( Darwin was a creationist,
> out to prove creationist theory when he took the voyage on The Beagle). But
> there was another historical phase of the science of natural history that
> was castastrophist.
> Then comes Darwin with gradualist , evolutionism. In a way, punctuated
> equilibrium integrates the earlier catastrophism with gradual evolutionism,
> at a higher level of the dialectical spiral of the progress of the science.
>
> In _Ever Since Darwin_ , Gould puts some emphasis on the mass extinctions in
> natural history. The origin of sex as the main form of reproduction (
> earlier it was cloning) , I believe is a main evolutionary result of one of
> the earliest mass extinctions.  However, by the Mayr thesis , I take it
> that, obviousl, not all speciation is in mass extinctions.
No, definitely not. When I brought up the much greater importance of the
physical
environment in the history of life, I wasn't referring only to mass
extinctions, which
are of course rare events. I meant any sort of change in the physical
environment, but
typically one of large consequences to an ecosystem.

In fact, one pattern paleontologists have observed is coordinated
stasis, which is where
many species in the same geographic location in the fossil record remain
essentially
unchanged over hundreds of thousands of years. The ecological
environment wouldn't
have remained stable over this time; what presumably triggers speciation
is large scale
change in the physical environment.

Brett, Ivany, and Schopf   ('Coordinated stasis: An overview.'
Palaeogeography, Palaeoclimatology,
Palaeoecology 127 (Dec.20, 1996): 1-20) point out that Herdman F.
Cleland back in 1903
noted notes something like coordinated stasis, points to the role of the
(presumably) *
physical* environment, and also indicates the perception (correct or
not) that this
pattern is inconsistent with Darwin's views (natura non saltum facet).

  Nearly a century ago Herdman F. Cleland (US Geol. Surv. Bull 206. 1903)
  captured the essence of coordinated stasis - the near absence of change
  in species and in regional fossil assemblages through geologically long
  time spans. In the summary to his monograph on the fossil faunas of the
  Middle Devonian Hamilton shales of central New York, Cleland made the
  following remarks:

  "In a section such as that of the Hamilton formation at Cayuga Lake...
  if the statement 'natura non saltum facet' is granted, one should,
  with some confidence, expect to find many - at least some - evidences
  of evolution. A careful examination of the fossils of all the zones,
  from the lowest to the highest, failed to reveal any evolutional
  changes, with the possible exception of Ambocoelia praeumbona. The
  species are as distinct or as variable in one portion of the section
  as in another. Species varied in shape, in size, and in surface
markings,
  but these changes were not progressive. The conclusion must be that,
  so long as the conditions of sedimentation remain as uniform as they
  were in the section under consideration, the evolution of brachiopods,
  gastropods, and pelecypods either does not take place at all or
  takes place very seldom, and that it makes little difference how much
  time elapses so long as the conditions of environment remain unchanged."
  (pp. 90-91)

Paul


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