Re: Darwin, Evolution, the Animal Kingdom, and Man

From: Lester Zick (lesterDELzick_at_worldnet.att.net)
Date: 12/04/04 

Date: Sat, 04 Dec 2004 19:22:18 GMT

On Sat, 04 Dec 2004 11:35:48 -0500, Wolf Kirchmeir
<wwolfkir@sympatico.ca> in comp.ai.philosophy wrote:

>Lester Zick wrote:
>[...]
>> Well, one of the things I'm trying to decide is the meaning of the
>> term environment in this context, whether it includes biological
>> factors internal to an organism in addition to the conventional
>> external environmental factors.
>
>Both. Any entity's environment is whatever is outside that entity. In
>the case of genes, such things as ambient temperature (external to the
>organism) can switch them on or off (see crocodiles). OTOH, the presence
>or absence of a neuro-transmitter can switch genes on/off in neurons.
>Since neuro-transmitters may be downstream from an external enviromental
>input, it's a matter of semantics what you call "the" environment in
>this case, but whatever you do, consistent usage is a must.
>
>[...]
>>>the cutters and pasters are RNA molecules, which are more likely to
>>>respond to environmental inputs that DNA molecules; which in turn means
>>>that environment can cause changes in the organism, albeit in a very
>>>roundabout way.
>>
>>
>> Or that an organism might cause change in itself.
>
>Same considerations as with reference of "environment." Eg, a human
>"changes itself" during puberty, when certain hormone levels (etc)
>change, certain genes are switched on/off, and development into an adult
>occurs. The timing of the hormonal changes is influenced but determined
>by extra-organsimic factors, such as nutrition, which determines
>fat-levels, which promote or inhibit the hormonal chnages; etc. So,
>which level of the environment is at work here?
>
>>
>>> Or that bacteria appear to have a mechanism that
>>>rnadomly rearranges DNA, which appears to be a major factor in the
>>>development of antibiotic resistance. And so on. It's much more
>>>complicated than random genetic mutation. {Any errors in the above are
>>>my own.}
>>
>>
>> Well, retroviruses also cause DNA modification. I wonder if
>> retroviuses might be a primary agent of evolutionary change?
>
>Likely, but not proven yet IIRC.

Yes, but if true would put a whole new spin on evolutionary mutation
including artificial mutation.

>>>Bottom line: evolution is the effect of the interaction between genes
>>>and environment. Neither can work withouit the other.
>>
>>
>> Yet my question returns to the issue of what exactly the environment
>> is relative to evolutionary genetic modification and the periods of
>> time over which it is reasonable to expect it to act? We already
>> suspect that evolutionary change proceeds by fits and starts rather
>> than continuous modification. So I think it is reasonable to ask what
>> agents might be at work apart from random mutation, which I have never
>> found to be particularly credible explanation for evolutionary change.
>
>Well, it seems that environmental changes are a major factor in
>triggering natural selection. That's why "punctuated evolution" was
>posited by Gould et al. But the extra-organismic environment can't cause
>natural selection if the genome lacks "dormant" genes that could have a
>positive/negative effect, or if it lacks physiological mechanisms that
>enable it to survive severe chnages in ecology, climate, or if it lacks
>pathways to genetic switches, etc. (NB that natural selection also
>explains the extinction of species, and also the stability of species in
>a stable environment. Extreme variations in a well-adapted species will
>usually reduce fitness, so such variations will be weeded out.)

I think the problem I have with natural selection is it merely kills
off poorly adapted specimens. No question it's true as far as it goes.
I just wonder if there isn't some agent of direction involved capable
of producing compound serial changes and adaptations. I'm thinking
that genetic modification even of substantial magnitude could happen
very suddenly but that extinction of species would happen very slowly.

>Random mutation may produce dormant genes, or may affect other
>mechanisms, such as sexual selection. OTOH, the sources I've read all
>indicate that 99%+ of random mutations either do nothing at all, or are
>lethal. The neutral ones may accumulate or disappear via genetic drift.
>
>In general, genomic variation in a species is an indicator of possible
>future speciation. Humans are in a bad way in the regard - we have very
>little genomic variation compared to, say, horses or dogs. Or even
>chimps, although primates generally have low rates of genomic variation.
>One source (can't recall details, sorry) claimed that the genomic
>variation in humans is less than that among the litter-mates of dogs --
>and keep in mind that these litter mates have the same dam and sire!
>IOW, we are genetically speaking all closely related -- siblings, in fact.

Damn, sire!

>> However, I certainly appreciate your comments, Wolf.
>>
>> Regards - Lester
>
>You're welcome.

Regards - Lester

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