------------------------------
A few hypotheses form the "central core" of evolution. They have been
maintained and included in nearly every version of evolutionary theory
from Darwin till the present. IMO, the "central core" includes:
I) Species originate by common descent through modification.
II) Genetic variations are produced via "random" processes.
(i.e. processes NOT caused by the organism itself, but
which are, in principle, statistically describable)
III) Selection pressures affect genetic makeup of the next generation.
These few hypotheses --- by themselves --- make almost no testable
predictions. They are, as Walter said, quite flexible and adaptable.
(They could, conceivably, be falsified by a dramatic observation. Suppose
a new species appeared suddenly, tomorrow, in several separate locations
around the globe. This would provide a counter-example to the first
hypothesis.) This flexibility is, at the moment, neither good nor bad.
It is simply a consequence of the predictive weakness of molecular
biology and developmental biology.
In order for this "central core" to make scientifically interesting and
testable predictions, it must be augmented by other hypotheses, hypotheses
about:
A) The elements of genetic information.
B) The inter-relatedness of genetic information in determining morphology.
C) The kinds of morophological changes which can be produced by mutations.
D) The source of genetic variation.
E) The frequency of mutations.
F) The ratio of harmful/neutral/beneficial mutations under various
conditions.
G) The strength of various selection pressures.
H) Typical population dynamics.
I) Mechanisms for reproductive isolation.
J) ....
With these auxilliary hypotheses, all sorts of testable predictions can be
made, predictions which can be verified or falsified. (Predictions, for
example, about the expected number of "transition" fossils, or the
expected degree of genetic homology.) As Walter pointed out, some
predictions of earlier versions of evolution WERE falsified. "Blending
inheritance" gave way to Mendelevian. Morphology was found to be (in most
cases) a complicated function of many genes. Gene duplications was added
as a source of variation. The evolutionary importance of small, isolated
sub-populations was reassessed.
As the data came in, all of these "auxilliary hypotheses" have been
debated, modified, and refined since Darwin's day, while the "central
core" has remained essentially unchanged.
(Unfortunately, the dichotomy between "central core" and "auxilliary
hypotheses" is still an oversimplification. Hypotheses can slip from one
category to the other. If I read my history-of-science correctly, the
hypothesis, "Natural selection is THE mechanism for distributing genetic
novelty through a population" was a central core hypothesis for many
decades. It was eventually bumped out of the central core by several
factors: sexual selection, neutral selection theory, punc. eq. population
dynamics. Today, the _degree_ to which natural selection plays a role in
stabilizing and/or changing allele frequency is a subject of debate, as an
auxilliary hypothesis.)
As Lakatos and Kuhn and other philosophers of science have pointed out,
this process of modifying and refining auxilliary hypotheses (to make the
total theory match observations) cannot go on forever. Auxilliary
hypotheses are themselves dependent upon observations from other areas of
science (e.g. developmental biology, molecular biology) which they must
not contradict. Auxilliary hypotheses should, ideally, be "progressive"
(increasing the empirical content of the theory and making new
predictions) rather than "degenerative" (_ad_hoc,_ serving only to explain
a specific observation). If the degenerative auxilliary hypotheses get
too numerous or too odious, the central core/paradigm gets replaced.
So what is my point? (Hmmm, what WAS it again? Oh yes, I remember:)
1) In most contexts, the term "Darwinism" refers to the "central core."
It would be quite improper (as some scientists have done) to claim that
the central core is "proven," since many of the auxilliary hypotheses
required to fit certain observations (e.g. Cambrian explosion, irreducible
complexity) are untested.
2) In some contexts, the term "Darwinism" includes auxilliary hypotheses.
It makes testable predictions and can be falsified. But because these
predictions rest upon MANY hypotheses, a "falsified" prediction results in
replacing one or two hypotheses, not the whole lot of them.
3) Walter argues that the flexibility offered by the auxilliary hypotheses
is a bad thing. I disagree. Other areas of historical science (geology,
cosmology) and observational/laboratory science (genetics, developmental
bio, chemistry, physics) operate the same way.
----------------------------------------
Walter didn't like my "test" of Darwinism.
> LH>... Moreover, there should be a mutational pathway, which does not
> >diverge too much from straightforward parsimony reconstruction, in which
> >every gene along the pathway codes for properly functioning products.
> >(This type of testing is possible with our current technology, and is
> >already being done for a few genes in a few labs.)
WR> That is not a test. Why? If we do not observe the experimental result
> expected by Loren, then evolutionists can always claim we haven't tried hard
> enough or long enough. Loren has not identified any *observation* that
> could conceivably refute evolution as false. He did the reverse! He
> offered a situation that might help confirm evolutionary theory as true.
> This is typical of so-called "tests" of evolution. They're phony, they
> don't test evolution, they don't place it at risk.
Walter, I get the impression that if you were around when the
Michaelson/Morrley experiment was being proposed, you would have said:
'That is not a test. Why? If we do not observe the experimental result
expected by ether, then ether-ologists can always claim we haven't tried hard
enough or long enough. M/M have not identified any *observation* that
could conceivably refute "ether" as false. They did the reverse! They
offer a situation that might help confirm ether theory as true.
This is typical of so-called "tests" of ether. They're phony, they
don't test ether, they don't place it at risk.'
As a matter of fact, if you _had_ said that, you would have been right
about everything except the first and last sentence.
The M/M experiment did NOT falsify the theory that electromagentic waves
travel in a medium of "ether." The M/M experiments were compatible with
an auxilliary hypothesis that "ether" was dragged around by the moving
earth. But this hypothesis was considered odious enough (and potentially
at variance with stellar observations) that the idea of ether was dropped.
The test which I suggested, above, is a prediction based upon auxilliary
hypotheses which most biologists currently believe to be true. If the
prediction is not verified, then scientists would have three options.
(1) Add a degenerative hypothesis. (e.g. "We haven't tried hard enough or
long enough.") (2) Add a dangerously untested but progressive hypothesis.
(e.g. by proposing a specific new mechanism for mutation or a specific
"backup mechanism" for the genes in question.) (3) Toss out the
central core.
As the history of science shows, any time a scientific theory finds itself
reduced to those three options, it IS at risk, and the test is NOT a
"phony."
-----------------
Walter also pounced upon:
> LH>Darwinists' knack for creating new auxilliary hypotheses is
> >frustrating to people who want to replace the entire paradigm,
> >but it is nevertheless a proper practice of science.
WR> The Darwinist's knack for creating new auxiliary hypotheses, (and for giving
> people the run-around with countless multifarious definitions -- and
> mis-definitions -- of their "core theory" versus the "auxiliary hypotheses")
> is frustrating to ANYONE who wants to test evolution. Loren is trying to
> blame evolution's untestability onto the "people who want to replace it."
No, that is not what Loren is trying to do! Grrrrrr.
Loren is trying to take an honest look at how all areas of science work
--- using the results and the vocabulary of some respected philosophers of
science --- and applying that to evolutionary biology.
WR> The remainder of Loren's discussion (though nicely stated) offers the usual
> evolutionary run-around. The usual run-around about a "central core theory"
> versus "auxiliary hypotheses"; and "natural selection" versus "sexual
> selection," etcetera. Lots to confuse the ordinary mortal, but none of it
> shows any testability of evolutionary theory.
Heh.
"The remainder of Loren's discussion (though nicely stated) offers the usual
cullinary run-around. The usual run-around about a 'central core flavor'
versus 'auxilliary additive'; and 'typical spoonful' versus 'isolated
sample,' etcetera. Lots to confuse the ordinary consumer, but none of
it shows any chocolateness of fudge ripple ice cream."
Seriously though,
the writings of Polanyi and Lakatos (along with Popper and Kuhn) can be
tough slogging at times, but if you want to make rhetorical capital out of
evolution's "testability" (or lack thereof), you really should pursue
them! To dismiss this as "the usual run-around" and "countless
multifarious definitions" is irresponsible at best, disingenuous at worst.
Ice cream comes in more than two flavors (chocolate or vanilla), and ideas
come in more than two types ("testable" or "structureless smorgasbord").
-----------------------------
O.k., o.k., I'm done (over)reacting to Walter's rhetoric.
Back to Popper. For now, I'll stick to my earlier claim:
... when Popper described [natural selection] as "unfalsifiable," he did
not yet have the categories of "paradigm" and "research program" available
to him. Those categories were later contributions of other philosophers
of science. The language of Popper's "recantation" suggests to me that,
over the intervening years, he had become aware of that category and its
role in scientific thinking.
--------------------------------------------------------------------------------
"You should always save hyperbole |
until you really need it." | Loren Haarsma
--Hobbes (_Calvin_and_Hobbes_) | lhaarsma@opal.tufts.edu