On Fri, 19 Jul 1996 Loren Haarsma wrote:
LH: "Hmmm, I've got a problem with those last four sentences.
Each, by itself, is fine, but taken together they seem to sneak
in a subtle but important shift-of-definition somewhere before
the last sentence."
First: welcome back Loren! Hope your vacation was re-creating.
You seem to firing on all cylinders - judging by the flood of
posts from you! Remember that you might be writing to folk
whose minds are a little tired and they they also need to have
a break - and whose logical processes might not be as sharp as
they should be :-)
I'm not wanting to "sneak in a subtle .. shift-of-definition",
and I welcome your feedback.
LH: "If I correctly understand your description of the German
group's work, David, the only types of "genetic linkages" they
looked for were: groups of existing species which could form an
inter-breeding set. (Species A can breed with B, which can breed
with C, which can breed with D, are all part of one set even if
A can't breed with D.) They did not, for example, quantify
genomic homologies between non-inter-breeding populations."
I'm not sure I can competently summarise the breadth of their
work. Certainly the identification of an interbreeding set forms
the core of their analysis. But it is supplemented by much other
data - interacting with a wide range of taxonomic and related
literature. To my knowledge, they did not quantify genomic
homologies between non-inter-breeding populations.
LH: "These sentences [...] imply that present-day "genetic
linking" should be taken as evidence of common ancestry. That's
fine with me. This sentence [...] is also fine, provided we
remember what "genetic linkages" means to this research group,
i.e. existing species which can form an inter-breeding set."
Three of the four sentences seem to be OK!
LH: "The final sentence:
> This is fully consistent
> with the scenarios developed by PCs and YECs.
is also true, but unhelpful, because their results are also fully
consistent with EC (or even naturalistic evolution). In other
words, the existence of reproductively isolated groups of
present-day species is no big surprise to anyone."
Maybe this is a "paradigm effect"? Maybe it is no big surprise
to EC and NE biologists - but I think you have got to admit that
this avenue of investigation has not been prompted by their
philosophy of "continuity". In my opinion, the German group are
the first since Linnaeus to show that there are natural
biological groupings that have the appearance of objectivity and
which can be tested. Compare this with other developments (like
numerical taxonomy) and I think the German work, even in its
initial stages, seems like a major leap forward.
LH: "The "subtle shift-of-definition" I complained about is the
implicit equating of "present-day genetic linkages" (as defined
by that research group) with common ancestry --- implying that
"genetic linkages" are the ONLY valid type of evidence for common
ancestry --- in which case EC would be in trouble."
I'm still trying to resolve where the difficulty lies...
These are my last two sentences:
DT: "Evidence for genetic linkages from these populations to any
other population is totally lacking. This is fully consistent
with the scenarios developed by PCs and YECs."
I'm not trying to "prove" that God supernaturally created
ancestral populations which have subsequently speciated. I'm
saying: if we presuppose that God supernaturally created
ancestral populations and that they subsequently speciated, how
can scientific techniques be used to analyse the situation? Is
it possible ever to gain an understanding of how many ancestral
populations there were? What are the implications for taxonomy?
and for studies of speciation?
I accept that genetic linkages are not the ONLY valid type of
evidence - but they are enormously important. Furthermore, they
provide some "meat" for PC and YEC-oriented biologists to develop
their ideas about discontinuity with some intellectual rigour.
I find this perspective very important for clarifying the issues
between evolutionary-oriented and non-evolutionary-oriented
biologists. Evolutionary biologists think they have reams of
data relevant to evolutionary change - but if modern-day families
represent their respective ancestral populations, evolutionary
biologists have no data that cannot be reinterpreted within a
framework of "variation within limits". I would go as far as to
say that a recognition of this alternative explanation of these
evidences means that evolutionary theory lacks the crucial
"proofs" of its validity.
LH: "I know that you weren't deliberately trying to "pull a fast
one," David. I just thought you'd like to know that your word
choice was implying things that you didn't intend."
I always appreciate your ability to analyse the rigour of
arguments. I'm grateful for the feedback on my post. I'm not
wanting to marginalise EC views - but my original reason for
writing was to contribute to the "After their kind" thread. I
wanted to indicate that although the "Genesis kind" is non-
technical, the idea that God supernaturally-created ancestral
populations of animals and plants (and mankind) is something that
is capable of fruitful scientific development.
Best wishes,
*** From David J. Tyler, CDT Department, Hollings Faculty,
Manchester Metropolitan University, UK.
Telephone: 0161-247-2636 ***