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

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

But they are eliminated immediately, within one generation, so in the
context of evolution they play no role whatsoever. They don't in any
way contribute to finding a high peak in "fitness landscape". So they
can be completely ignored in explaining to newcomers what causes
evolution to yield new species better than ever before.

> Selection pressure, a term that you disparage, occurs only after
> mutation has introduced the new allele into the mix.

It's an illogical composition of words. The so-called "pressure" acts
upon statistics of populations, increasing the frequency of one allelle
at the expense of another. The so-called "pressure" is caused by
differential success at full-cycle success, which is a conflation of
fecundity-number and survival-probability. (If the fecundity-number is
6, and the survival-probability is 1/3, then the full-cycle growth
factor is 6 * 1/3 = 2, i.e. twice as many individuals each generation
as the one before, which of course continues only so long as conditions
are the same, in particular conditions change almost immediately due to
limits to resources available, hence the typical exponential expansion
followed by slowing down to linear followed by slowing down to
exponential-decay-from-full-filling-of-habitat, the S-shaped growth
curve. (For full-cycle growth factor less than 1, the allelle frequency
shrinks exponentially to zero until the total number of individuals is
so small that computing exact probabilities of different sizes of
populations is better than the exponential approximation.)

A more accurate compositon of words would be something that includes
the word "change" and the phrase "population statistics", but I can't
think of any reasonably brief such composition.

So you like the misnomer "selection pressure" while I dislike it.
Big deal.

But we agree on the science, that the directional bias in the expected
change in population statistics, caused by difference in fitness,
happens *only* after there are two allelles that have different
fitness, one allelle ancestral and the other generated from it by
mutation. (Or if there's another mutation before one of the first two
allelles has gone extinct, then there will be three alleles at the same
time, with more complicated math but the same basic idea.)

> Nothing in my
> statement even suggests that I am listing all the factors behind
> evolution. I am only describing one of them.

The actual factor is a stochastic relationship between individuals and
the live/die or make-N-babies result, whose expected mean is based
purely on the two fitnesses, but whose standard deviation is based on
population size and the nature of the environment (nice and stable
gives small s.d. whereas lots of unpredictable disasters gives large
s.d.).

That one factor can be analyzed per mean and s.d. separately, thereby
separating bias from noise. Since the bias (mean) is caused by fitness
difference, I accept if you call it one factor instead of only part of
one factor.

> 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.

"A half truth is a lie."
Evolution has three factors:
- Ideal replication of genome.
- Mistakes in replication, or mistakes in maintaining DNA between acts
of replication, which generate new allelles.
- Change in allelle frequencies, which is stochastic, which can be
analyzed as part bias (mean change, or "selection pressure") and part
noise (random drift).

Only that third factor deals with populations (statistics thereof).

When you say "the population nature of evolution", your words could
mean either:
- *The* (one and only) nature of evolution *is* population based.
- There are several natures of evolution, and population is just one of them.
The first is false. The second is true.
Your words could mean either of them, I have no idea which you meant.
Please state which you meant.
..

.

Relevant Pages

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