First, the following claim is made:
While it is certainly true that selective processes can cause the
average characteristics within a population to change, this is not
evidence
for evolution. This is because evolution of this kind is a
mathematically
necessity when four conditions are met (Ridley, 1993):
1. Creatures reproduce.
2. Creatures inherit physical characteristics.
3. Physical Characteristics vary from parent to offspring.
4. Physical characteristics effect the survivability of
creature.
I don't think that that is quite right. In a stable situation where the
only variations are in the direction of reduced fitness, all the above
may be true, but natural selection will act only as the "executioner of
the unfit", and there will be no evolutionary movement - not even
microevolution - at all. In fact, Darwin was stymied by that fact for
some time. In any case, the above four do not "mathematically" entail
microevolution.
The pamphlet goes on:
In other words, this evidence for evolution MUST be present unless God
did
one of 8 things:
1. Change laws of mathematics (2+2 = 5?).
2. Make creatures that cannot reproduce.
3. Make physical characteristics non-hereditary.
4. Make children identical to parents.
5. Eliminate death.
6. Make the process of dying unrelated to physical
characteristics.
7. Eliminate mutation.
8. Not allow mutation to effect hereditary characteristics.
I don't think that that's quite true either. Take the scenario I just
sketched, and allow only suitably harmful mutations. The original four
conditions will be true, God will not have done any of the above eight
things, and there will be no microevolution.
The pamphlet continues:
What does this mean in terms of evidence for evolution? Remember
that when scientists compare two theories, they compare differences
between the predictions of the theories.
That's a bit oversimple. Theory discrimination and selection still goes
on even when the theories involved are empirically equivalent. For
instance, the Copernican and Tychonic systems were empirically
equivalent astronomically - and easily proven to be so - but the
Copernican theory won that competition hands down on the basis of a
number of philosophical considerations thought to be scientifically
important - elegance, "simplicity", and perhaps some other harder to
define considerations. (And of present relevance, some versions of
progressive creation *may* be empirically indistinguishable from
evolutionary theories - but that hasn't seemed to stop anyone from
choosing sides here.)
It is also claimed that:
"Micro" evolutionary processes result in small changes that
usually
disappear when the environemntal conditions driving the evolution
change.
Is that true? When conditions are _reversed_ they may disappear
(peppered moth, finch beak size, etc.), although I've never seen any
discussion of how typical that is. But they disappear when conditions
merely change? Are there data supporting that claim?
The final claim is this:
Furthermore, evidence of "micro" evolution does not contradict a theory
of
intelligent design unless the designer is supposed to have created a
world
that did not meet the four criteria listed above; it is mathematically
impossible for "micro" evolutionary evidence not to be there otherwise.
Given these two considerations, the evidence of evolution occurring all
around us is not strong, much less conclusive, evidence for the
proposition
that all life descended from a common ancestor by natural processes.
What that comes to, I take it, is that if some bit of data is not
inconsistent with a theory and is indeed expectable on that theory, then
those data cannot constitute strong evidence for some alternative
competing theory. That claim does have some plausibility, but I think
that we have to be careful here. Given the general underdetermination
of theory by data, every theory always has possible competitors, each of
which is consistent with all the data in question and, indeed, from each
of which that body of data is derivable. One doesn't want to adopt a
principle which, in the light of that underdetermination, would imply
that no data ever constitutes strong evidence for any theory. The
relationship of data to theory and the whole area of confirmation are
pretty tangled, and I am a little nervous that the principle underlying
the "conclusion" section of the pamphlet may not do full justice to some
of those tangles.
Del Ratzsch