Re: Musings about the Cambrian Explosion


"Jim McGinn" <jimmcginn@xxxxxxxxx> wrote in message
news:dhv9kv$1mch$1@xxxxxxxxxxxxxxxxxxxxxx
>
>> FACTORS IMPACTING THE SO-CALLED EXPLOSION:
>>
>> Rate of mutation:
>
> Opportunity is the underlying cause of increase in
> diversity/mutation/rate of evolution.

Jim, I am flattered to know you agree with my intuitive assessment (not
picked up from any other source, but not suspected of being original, by a
long shot, since it would seem pretty likely).

But the recipe consists of more than opportunity (and opportunism).

Let me try to outline the recipe as brainstormed so far:

I. Early "characteristics" of life (both in packages we conceive of as
"living things" and in packages of
one or more, but insufficient for us to conceive of as "living things."
(Will list some of them in a later message). Opportunity and opportunism in
the "getting together" of various packages. And, of course,
relatively greater capacities of SOME constellations of "life
characteristics" to prevail more opportunistically than others.

2. Opportunity to grow into/onto 'virgin geography' not only in relation to
conditions which would support certain 'life characteristics packages,' but
ALSO the following:

a. Opportunity to spread *in absence* of more progressed OTHER 'life
characteristics packages' (hence little or no competition) from other 'life
characteristics packages;'

b. Opportunity to spread *in absence* of any evolved predators (in early
stages);

3 Constraints of growing into "virgin territory," where, opportunity was
*mixed* with challenges of growing unders circumstances *different* from
those that screened the mutations of ancestoral 'life characteristics
packages';

4. Constraints of encountering new and different kinds of corruptors of
duplication mechanisms (I hesitate to say DNA, just yet, because I do not
have a clue as to when DNA or RNA entered the picture, or how, or at what
stage of the "tryouts," as it were. of various constellations of life
characteristics in
'life characteristics packages.') What might some of these have been?
Consider:

a. Different amounts of radiation from different areas of Earth's surface
and solutions of chemicals in water;

b. Variations in the angle of the sun to Earth at new localities and,
hence, variations in the amount of
radiation exposure to the sun (and, of course, any 'life characteristics
package' that lived under snow for
eons eventually got exposed directly to sunlight;

c. Variations in the chemicals at various places on Earth's surface (Dirt
and rocks consist of many
variations in amount and kind of chemical elements, which vary from place to
place);

d. Mechanisms (and, eventually organs) of self-replication or reproduction
had to evolve by way of
greater or lesser ability to both survive and *be unscrambled* by various
radiation sources, toxic substances, heat variations, etc.

This is not exhaustive. But is representative of some of the kinds of
variables that SURELY must have served to screen different mutations in
different locations at different times.

But so far my imagination allows me to visualize all the foregoing factors
and STILL not come up with anything of the nature of a diversity
'EXPLOSION.'

Let me try to put it this way. Opportunity neither opportunities nor
challenges were homogeneous. They varied from place to place and from time
to time even in a single place, as "packages of life characteristics" also
did not remain homogeneous. Different mutations encountered different
complexes of both, but offered some consistencies (such as climate cycles)
in some areas over long periods of time.

This would account for diversification as a part of spread, in opportune
times and places.

What nags at my mind, however, is whether there could have been ONE OR
MORE factors -- especially something that corrupted the replication or
reproduction mechanisms DIRECTLY.
Hence my curiosity. Could there have beeen, during the Cambrian explosion,
not only the factors of
heterogeneity of geography as 'life characteristics' proliferated, but ALSO
some factors that monkeyed with the reproductive or replicative processes
THEMSELVES.

Let me ask that we keep in mind that gametes and immune systems, and
protection of organs as they
evolved would not have been present from the outset. If a kind of
replicating 'creature' developed testicles that dragged the ground, for
example, walking over a rock with relatively higher radioactivity, or hotter
than surround rock, or dirt containing, say, a higher than average amount of
potassium cyanide,
would NOT have the same effect as upon the testicals of a creature with legs
five feet long.

No attempt to be fecetious here, but as replication followed replication,
and sexual reproduction followed sexual reproduction, mutations would NOT
have provided merely differences in gametes but ALSO differences in the
vulnerabilities of the gametes of one creature as compared to those of
another.

In short, I just have a nagging hunch that -- along with all the factors
which would have influenced diversification, as life characteristics spread,
in many different mixes, and with many different screening characteristics,
indirectly impacting what mutations would "work" and which would not, no
EXPLOSION of diversity in the Cambrian need, necessarily, to have occurred
only from that. But changes to the REPRODUCTIVE MECHANISMS/ORGANS
THEMSELVES could have accounted for a JUMP in diversification.

Obviously then, I am not trying to grope only with the simple issue of
opportunity and opportunism.

The movie in my head is a lot more complex than just that.

Thank you, Jim, for the input. Please come back with more, addressing other
issues cited above.


g
>
> Jim
>
>


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