Robert L Trivers wrote:
RT> Derek McLarnen wrote a respectable overview of evolutionary
mechanisms.
> Herein, I post a few comments and corrections:
Thanks for taking the trouble.
DM> >Neo-Darwinian evolutionary theory claims that the most significant
cause
> of evolution is the adaptation of populations of living organisms in
> response to environmental changes.
>
RT> No, this is Darwinian not Neo-Darwinian theory.
True. All through my message, I was comparing neo-Darwinian theory with
Punctuated Equilibria, not classical Darwinian theory. For that reason,
I did not make a distinction between Darwinian and neo-Darwinian theory.
> DM>Much more common are chromosomal changes (deletion, duplication,
> inversion and translocation of chromosome parts). More common still
> are "crossing-over" >events that occur during mitosis and meiosis.
>
RT> "Crossing-over" is a term restricted the paired homologues
> during meiosis.
True. It occurred to me that I had better check that before I sent it,
but I forgot and it slipped past me in the pre-sending revision.
> DM>Natural selection is a higher-level neo-Darwinian mechanism.
>
RT> No, again this is simply a Darwinian mechanism.
See above.
> RT>Other high-level neo-Darwinian mechanisms are allopatric,
> >parapatric and sympatric speciation, coevolution and extinction.
>
> Yes! However, these are not mechanisms in the strict sense.
How about processes composed of sub-processes. I admit that mechanisms
is not the ideal word.
> DM>Genetic drift is also arguably not a neo-Darwinian mechanism.
>
> It is -- In fact Wright's work is a cornerstone of the modern
> synthesis.
No excuses for me here.
> DM> This is best seen in the comparison between two
> >non-interbreeding populations of the same species living in
> >very similar environments. It will be noted, over time, that
> >the populations will start to vary from each other, not in
> >response to environmental imperatives, but simply as a
> >result of the accumulation of different random mutations and
> >chromosomal changes that, while they may affect appearance,
> >do not significantly effect environmental fitness.
>
RT> Genetic drift is indifferent with regard to adaptive
> consequences. Allele fixation or extinction are stochastic functions.
That was what I though I had implied.
Regards,
Derek
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