This objection to the creationist arguments do help us in this
exchange. Where there is a lack of evidence, there is scope for
much speculation. The two creationist arguments cited are based
on the idea that substantial astronomical and cosmological models
are being built on assumptions - their error is in failing to
enquire what kind of evidence is needed to support the models.
Gordon Simons has helpfully asked for discussion of this point -
what evidence can be regarded as having a bearing on the question
of biological variability? My concern here is WHENEVER SOMEONE
IS ADVOCATING A MODEL OF THE REAL WORLD, THE ONUS RESTS ON THEM
TO JUSTIFY THAT MODEL. Where neoDarwinists advocate no limits
to variability, they must carry the responsibility to defend this
position. Otherwise, neoDarwinism must remain a hypothesis
awaiting testing of its fundamental assumptions. Similarly,
where PCs and YECs propose a model of the animate creation which
involves limited variability, they carry the responsibility to
justify that position. My response to Gordon is to say that we
must start with the data we have - and ask what do we make of it?
Looking back over the messages, I find several specific arguments
for limits (from myself on 25 July, 26 July and from Arthur
Chadwick on 2 August. Apologies if I've forgotten other
contributions). These come under three headings:
(a) Artificial breeding. Breeding without mutations comes up
against limits (cow milk yields, sugar beet content) and problems
of non-viability without human help; breeding with mutations show
that genetic information can be juggled and mixed in many ways -
but new information (to break through limits) is elusive
(Drosophila, E. Coli). Mutations have never been thought of as
a significant part of plant or animal breeding programmes.
(b) Natural breeding. Speciation is possible, but descendants
of ancestral forms exhibit a limited range of features (ciclid
fishes, Hawaiian plants of the Compositae family). It is
possible to group organisms into Basic Types - which have an
objective link obtained via hybridisation studies. These are
usually, but not always, at the Family level. Basic Types have
similar developmental pathways.
(c) Complexity. Complex structures are not able to vary far
without a drastic loss of function.
Evidences for variation are the common property of macro-
evolutionists and non-macro-evolutionists. We must object if
people appeal to evidences of variation without addressing
alternative models for understanding the data. It seems to me
that those evidences we do see (summarised above) are best
understood within a framework of limited variation. I have yet
to see a neoDarwinian explain in a convincing way that these data
are indicators of no limits to variation.
*** From David J. Tyler, CDT Department, Hollings Faculty,
Manchester Metropolitan University, UK.
Telephone: 0161-247-2636 ***