You indicated that you took "the most damaging argument against Mike [to
be] the argument from
pre-adaptation or exaptation."
That is, I think, an important consideration (and, althought not in its
biomolecular version, the idea goes back to Darwin). (And I've had some
discussion of my own with Mike about it.)
But though exaptation (I think) *has* to be admitted as a relevant
consideration, it does not necessarily close the issue either. What it
represents is one possible scenario for either restricting the scope of
or more fundamentally undercutting Mike's argument. But which it might
do - if either - or the extent to which it requires a restriction in
scope is an empirical matter. The possibility of exaptation does indeed
show that the generation of irreducibly complex systems is not *in
principle* and *absolutely* impossible. But Mike does not claim that it
is in principle absolutely impossible - indeed, he in fact believes that
some very simple but still irreducibly complex systems can arise even by
purely chance means.
But that mere possibility doesn't generate much mileage - the question
is merely transmuted into a question of (among other things)
probability. How wild are the probabilities? I would guess that (a) no
one really has much clue, but that (b) in some instances they are
extreme. If so, the scientific and practical impact of the relevant
mere possibility may be more or less in the same category as some of the
more outrageous quantum possibilities.
In any case, relevant questions remain even with the admission of the
exaptive possibilities. The usual scenarios (such as the ones you
sketched) typically require e.g.,that the relevant componants for an
adaptive function/characteristic originate and function in some
(usually) adaptive way, be available, suitably relatable to each other,
manage to get together in the right way, etc. I have no particular
problem with there being cases of that sort. But if that is going to be
the *general* explanation for the emergence of the relevant sorts of
complex functional novelty, that is going to have to happen with what
seems to me to be astonishing frequency. How many separate times would
that sort of exaptive scenario have to have happened to have generated
the quantity of novelty which the history of, say, mammals would
require?
So when you say:
"The original system that
produced the useful function did not arise by Darwinian selection and
gradualism, rather it arose by the novel combination of the parts that
functioned for other purposes in other systems."
what are our best estimates as to the prospects of that happening - by
chance - in specific cases, and how many of those sorts of specific
cases are we likely talking about? And are those sorts of numbers
really reasonable? I don't have much idea about what those numbers
might be, but citing a few cases and appealing to mere possibilities
does not, it seems to me, constitute a really devastating response to
Mike.
Here's another relevant question. The cited scenario assumes that once
there is a glimmer of an adaptive function/characteristic (having arisen
by either fortuituous or law-aided assembly of spare parts from other
systems, that Darwinian processes will unproblematically drive it to
higher levels of perfection. That, again, may well be possible. In any
case, I don't propose to deny that possibility.
But I don't know of any reason to think that that can happen in general,
and for arbitrary cases. It may be possible, but it is (at least, I
would think) equally possible that in lots of such cases there simply is
no appropriate increasing fitness path - at least, none that would
support any reasonable expectation of getting there by any available
mutation-driven route.
But in saying:
"Once that novel function is
useful, no matter how poorly formed initially, it is selected for and
via
selection fine-tuned and perfected.
That, again, may be a possibility, but how might one know that to be the
general case regardless of the specific instance in question - as your
above perfectly general claim seems to suggest? I would think that that
would be an empirical question. And that is basically Mike's contention
- that that is an empirical question to be decided by investigating
cases, and his basic demand is "show me the pathway".
You say:
"The question which now arises is "are these "molecular machines"
flexible
enough to reassemble into novel, potentially useful, structures. Well,
I
happen to think that the answer is yes. Behe seems to think no."
I'm not sure that that's quite right. The question, I think, is - are
these things flexible enough to generate anywhere near all the novelty
in question?
A bit later, in reference to the machine analogy, you say:
"We are only
scratching the surface of the range of protein-protein and protein-DNA
interactions that occur in the concentrated molecular environment of the
cell. Most biochemistry, has been conducted in dilute aqueous solution,
that only remotely resembles the conditions in the cell."
Well, I would think that that sort of admission might be good grounds
for a bit of caution, especially where universal claims were being made.
You take that is opening up wide scope for natural processes generating
biochemical novelty. And maybe that's right. But if that is right, is
it just obvious that that need upset Behe? His case is that certain
sorts of intricacy speak of designedness, and your suggestion here seems
to be that the subcellular environment may be even more intricately
organized than anyone previously suspected. Well, that might be
perfectly OK with him.
As mentioned in my earlier post, Mike is not averse to irreducible
complexity being produced by natural means. (He is not opposed to
evolutionary common ancestry, either.) I *think* that his preference is
that relevant information be incorporated into precise initial
conditions rather than in the detailed structure of laws and lawful
processes, and I would *guess* that his prediction would be that it will
turn out that when the dust has settled, the hope that
self-organizational principles, special processes of the sort you were
referring to earlier, etc., will turn out not to do the job.
Concerning your sicle-cell example. You say:
"But did it
arise by evolutionary means--no doubt. Did it arise by Darwinian means?
Well, not exactly. [snip] So the new machine arose not by selection or
gradualistically, but by principles of self-organization and suddenly.
[snip] Obviously, this is a simple case, because the new machine is
simply a
rearranged version of an old machine."
I'm not sure that there is anything in there that Behe would have to
deny. It isn't Darwinian, and it involves mere rearrangement of some
already-present complexity.
But what I think he would find interesting is your comment that:
"it
doesn't seem to me to be such a far fetched first step in the evolution
of
some new structure and function."
Howard was (apparently) accusing Mike of arguing merely from his
inability to imagine workable paths. But the above sounds *very* like
simply the flip side of that sort of intuition. Is the generalized
assertion that paths are imaginable the core of the case against him?
Del
Del Ratzsch voice: (616) 957-6415
Philosophy Department (616) 451-4301 (home)
Calvin College e-mail: dratzsch@legacy.calvin.edu
Grand Rapids, MI 49546 fax: (616) 957-8551