Re: Bipedalism and theorizing... was Re: Morgan and creationists
John Waters (jdwaters@dircon.co.uk)
28 Sep 1996 17:33:00 GMT
Paul Crowley <Paul@crowleyp.demon.co.uk> wrote in article
<843593383snz@crowleyp.demon.co.uk>...
> In article <01bba9fd$483b81a0$152470c2@jdwaters.dircon.co.uk>
> jdwaters@dircon.co.uk "John Waters" writes:
>
> > JW: Generally speaking genetic adaptions occur under one of
two
> > sets of conditions. The first type of condition occurs when
the
> > global climate changes from cool dry to warm wet. This is
> > significant because there are more potential ecological
niches
> > in a warm wet environment. Under these conditions you get
the
> > radiation of specie as they adapt to these new niches.
> > [snips]
> >
> > The marginal variant specie are typically generalistic
> > omnivores. The specialist mainstream specie tend to be
> > frugivores, or carnivores, or leaf eaters, or graziers.
>
> We're really talking about all species - fauna and flora. Are
> such rules well recognised? I've never heard of them.
Clearly
> if whole species are wiped out by drastic climatic change
(such as
> that at the K/T boundary) then new niches open up, enabling
rapid
> radiative adaptation. But does it apply to normal climate
change?
>
> Paul.
JW: These are pretty big questions Paul. I could answer them in
great factual detail, but judging from your reply to Gerrits
letter of 25/09/96, you are not really interested in a
regurgitation of the text books. In view of the fact that
general and human evolution are covered by over forty scientific
disciplines, this is probably just as
well.
So my reply here will be fairly generalist and simplified.
Nevertheless, it should be sufficient to convey my limited
understanding of the processes involved and my present level of
knowledge (and ignorance) on the subject. Hopefully, it will
provide
an agreed framework -- which will allow us to continue our
debate on hominid evolution.
Looking back to previous correspondence, I see I prefaced one of
my early sentences with the words -- In the Pliocene... I can
see now that I could have been more succinct. For this I
apologise. So let me start again, -- In the Pliocene Epoch. (As
you know, the Pliocene Epoch is classified by palaeontologists
as the period of time between 1.8 million years and 7 million
years B.P.)
According to paleoecologists, paleobotanists, paleogeologists
and palaeontologists, there was a marked cooling trend
throughout the Pliocene Epoch. This contrasts with the previous
Miocene and Oligocene Epochs which were relatively warm and
stable.
I prefaced my remarks with the term Pliocene Epoch because this
is the epoch in which most of the crucial physiological changes
took place in the hominids. These changes continued into the
Pleistocene Epoch, particularly in respect of neurophysiological
changes.
Although there was a long term trend from warm wet to cool dry
in the Pliocene Epoch, the period was by no means stable. There
were many variations of temperature and humidity, known usually
as glacials and interglacials. In the cool periods, many specie
of plants and animals became extinct. While in the warm periods
there was an expansion of faunal and floral specie and total
populations.
This has been shown by an examination of the related geological
strata throughout the world. The strata are consistent on the
matter of extinction and expansion of specie. Of course, the
fossil beds are relatively few and far between. But short of
digging up the whole of the Earths crust, it seems doubtful if
we will ever get a more
(statistically) complete set of data.
And so to your questions.
>> The marginal variant specie are typically generalistic
>> omnivores. The specialist mainstream specie tend to be
>> frugivores, or carnivores, or leaf eaters, or graziers.
> We're really talking about all species - fauna and flora. Are
> such rules well recognised? I've never heard of them.
JW: I was talking about mammals here. The terms frugivores,
graziers and leaf eaters are not normally applied to flora.
Nevertheless, the processes of genetic adaptation and natural
selection apply to allspecies of life. I think the concept of
specie radiation applies to both plants and animals. For
example, Pedunculate, Sessile and Turkey oaks would be an
example of a radiation of flora. Similarly, Lions, Tigers and
related variant specie would be a example of a radiation of
fauna.
I dont know of any examples of flora which have evolved by
means of the marginal variant evolution process. I would guess
that it should be possible for sexual species of flora, but I
cannot see how it could happen with asexual specie. By contrast,
the marginal variant evolutionary process is virtually a norm
among sexual specie of
animals. This is the process under which one class of animals
evolves into another class. For example, fish into amphibians,
amphibians into reptiles, reptiles into birds, birds into
monotremes, monotremes into marsupials, and marsupials into
placental mammals.
My terminology may be a bit ancient. I think the current term is
Centre to Edge adaptation. However, I dont think this has been
officially classified as yet. (If Dan Barnes is reading this
article, I hope he will be kind enough to supply the most up to
date terminology.)
As far as I am concerned, both the initial stages of radiation
of specie, and marginal variant evolution, are achieved by
selection rather than long term genetic adaptation. The later
stages of evolution of both types are then determined by long
term genetic
mutation and selection.
(I think I will have to make this a three part answer, Paul. The
second part will deal with your questions on power to weight
ratios, while the third part will bring us back to hominid
evolution.)
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