Re: Part 1 (of 3): What are major aspects of evolutionary theory?

On Tue, 13 Dec 2005 23:16:18 -0800, anon1@xxxxxxx wrote:

>> I never cared for the "fitness landscape" metaphor because it assumes
>> that fitness is a continuous function of whatever is on the axes of
>> variation. These are not continuous parameters and subtle changes in
>> regulatory genes can produce rather abrupt and discontinuous changes
>> in phenotype, hence in fitness.
>
>I suppose the rationale is that most non-fatal mutations are really
>tiny steps, and a continuous landscape is a reasonable mathematical
>model for a descrete but very finely-divided staircase. Really huge
>regulatory changes usually screw up the overall interlocked system so
>badly as to be virtually always fatal. Or such changes make one
>individual totally incompatible with all other members of what was his
>species, so even if he can survive, he can't produce offspring. So most
>of the time giant steps can be ignored as a course of evolution. But
>all it takes is one such giant mutation to succeed every few million
>years, something making an allelle very much more successful than the
>ancestral allelle, yet not mating-incompatible, and suddenly there's a
>big evolutionary jump. So maybe the correct metaphor is a fitness
>landscape with the ability of individuals to shout "Geronimo" and jump
>into a strong breeze with a hang-glider and take their chances where
>they might land on a new island far from home.

Those fatal mutations are also quite striking discontinuities in the
landscape.

>> Still, the fact is that evolution is always about populations and
>> never about individuals. Selection pressure changes the allele
>> frequency in a population.
>
>You're seeing only half the picture of evolution, the half whereby
>already-exiting variation is tested and only the best is retained.
>You're overlooking the other half of evolution, whereby one individual
>suffers a mutation whch changes the fitness of that individual and of
>any descendents that individual might begat, thereby adding new
>variation to the population. That individual's mutation, and the
>mutations within other individual, are essential for evolution to
>produce new characters rather than merely narrow down the whole world's
>life to a single genotype.
>
>The anti-evolutionists, who claim evolution can only purify the race,
>never produce a new race, make the same omission you made there. You
>are playing into their hands, giving them quotes to mine.
>.

Selection pressure, a term that you disparage, occurs only after
mutation has introduced the new allele into the mix. Nothing in my
statement even suggests that I am listing all the factors behind
evolution. I am only describing one of them. I was also making the
extremely important point that you seem to have missed in earlier
posts, and whose significance you snipped away, about the population
nature of evolution.


.

Relevant Pages

  • Re: Speculative Design Hypothesis (with predictions)
    ... So where is the testable falsifiable hypothesis for how evolution ... so why hasn't our species been extinguished by random ... they depends on the environment plus all the other erstwhile mutation. ... You speak of "miscopying" as the source of variation. ...
    (talk.origins)
  • Re: Is evolution more then mutation and selection?
    ... I recommend rereading Darwin, as well as more ... modern books on evolution. ... The shifts in fitness ... ] mutation tend, on the whole, to be ...
    (sci.bio.evolution)
  • Re: An introduction
    ... selection and an oversimplified concept of mutation via genetic ... variation, but it speaks little to the source of variation. ... and itself is a stronger force of evolution than mutation. ...
    (talk.origins)
  • _Plausibility of Life_ -- facilitated variation in evolution
    ... Darwin's revolutionary theory of evolution has explained very well how ... The authors emphasize early on that mutation only alters what already ... for the evolved organism. ... is done centers on the notion of `facilitated variation', ...
    (talk.origins)
  • Re: Is the complexity of evolutionary change explainable?
    ... there will be no differences in mutation effects. ... I'll make a transition from nucleotides to genes with this ... It looks like you are making an argument for rescaling the total amount of mutation to account for the fact that the evolution of the human only used a small ... And these peaks can be quite low in fitness and prevent a global peak from being found. ...
    (talk.origins)