Re: Reproductive Selection

On Dec 16, 7:33 pm, Treus <treusd...@xxxxxxxxx> wrote:
John Harshman wrote:

<snip>





In other words, how do the novel features of R(S2,x), meaning the
reproductive compatibility particular to S2, originate when the
relevant differences between S1 and S2 can't be accounted for by
genetic drift alone?

Reproductive compatibility doesn't arise. This idea of "novel features
of R(S2,x)" is meaningless. At most, it's maintained by the absence of
incompatible genes. Compatibility within a population does not require
this "backward-compatibility" you keep talking about, as; the 2-allele
model shows. Why do you keep ignoring it?

If R(S2,x)>R(S1,x) for *any* x, then where did that new functionality
of S2 with respect to S1 come from, if not drift or reproductive
selection?

It's not functionality. It's just a consequence of having compatible
genomes. Do you understand that the 2-allele model features neither
drift nor "reproductive selection"? And yet it maintains compatibility
within populations while producing incompatibility between populations.

The two allele model does not sufficiently account for the complete
set of traits uniquely necessary to the RC of a population arbitrarily
different from whatever ancestor is taken as the starting point.

Presuming I understand your jargon right, yes, it does. You can
simply apply the two allele model repeatedly at different loci to
generate as large a difference as you like. Equally, once the
reproductive incompatability has been introduced (via, for example,
the two allele model) there's nothing keeping the populations from
diverging drastically by drift, and/or environmental and sexual
selection -- which is to say diverging arbitrarily.

Consider, again, the other model, where "incompatability" at each
generation is small (within the average variation of the population)
but, by progressive increments over many generations, large
incompatbilities can be introduced. This is the "great dane can't
breed with chihuahua" model. Such divergence, with small incremental
steps, doesn't have any clear bounding on it, thus, given enough time
for enough small increments, incompatabilities can be arbitrarily
large. What you really need to demonstrate is some reason why there is
a finite upper bound on how many small increments can accrue. You
haven't done that.

fnord

.

Relevant Pages

  • Re: Reproductive Selection
    ... Reproductive compatibility doesn't arise. ... of S2 with respect to S1 come from, if not drift or reproductive ... The two allele model does not sufficiently account for the complete ...
    (talk.origins)
  • Re: Reproductive Selection
    ... Reproductive compatibility doesn't arise. ... of S2 with respect to S1 come from, if not drift or reproductive ... The two allele model does not sufficiently account for the complete ...
    (talk.origins)
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