David Tyler wrote:
> Rich Daniel wrote:
>> In a very few years, we'll know the complete DNA sequences for
>> man, chimp, and gorilla. I'll make you a bet: There will be no
>> human genes that are not also in chimps and gorillas, with very
>> minor differences....
DT> I know you have offered this "bet" to Paracelsus, but before
DT> this exchange gets too polarised, I would like to inject the
DT> thought that creationists have no reason to take you up on it.
I think one major reason not to take it up is that it's no longer
a terribly viable position to maintain. We already know that
humans and apes share many homologies.
DT> Design considerations suggest that the task of DNA is very
DT> similar for Apes and mankind - the DNA ought to be very similar.
This is not true. Today there is no good reason to believe that
DNA sequences must map uniquely to a particular biochemical
system or morphological form. That life appears similar today
doesn't mean that this similarity is necessary. I would suggest
that the number of _possible_ genomes that could produce the
human form greatly exceed the number of genomes which actually
display substantial sequence homologies to those of the great apes.
Even with exact matches of protein sequences, the redundancy of
the genetic code and the flexibility of regulatory sequences and
gene order might be able to place us closer genetically to lemurs
than chimps. All this suggests common descent and historical
contingencies: whether the overall mechanism behind descent was
"natural" or "special" is the real question that remains (IMO).
RD: Ah, but Paracelsus made the claim that humans are irreducibly
RD: complex. I interpret this as meaning that we have physical
RD: structures that cannot have evolved from an apelike animal.
RD: This in turn would imply that we have genes that cannot have
RD: evolved. If something different was intended, please clarify.
Mike Behe was asked similar questions when he visited talk.origins
once. If some biochemical system is said to be irreducibly complex
and therefore could not have evolved (or so the reasoning goes),
shouldn't the IC system have appeared suddenly within a particular
lineage? If IC requires ID, then there is no a priori reason to
suppose that the components of IC systems should display hierarchical
patterns of nesting. One suggestion Behe made to circumvent the
problem was to posit that the components of future IC systems were
already "inside" the original cell, tucked away and waiting for the
right time to be used, several billion years down the road.
Personally, I find the "strong" version of that unlikely -- The
strong version being that the systems were safely stored as
inert sequences in the genome over the eons. The "weak version,
that the sequences were in use in other systems throughout the
development of life sounds a bit more likely to me -- And a bit
more like contemporary versions of evolution.
Frequently, "common design from common designer" is mentioned
as another possible explanation. But this suggestion neither
implies nor requires an overall, hierarchical pattern to life
(a pattern that tracks consistently in time, morphology and
Actually, I take that last comment back -- common design can
suggest hierarchical groupings if we also suppose that the
development of organisms was limited by historical contigency
(which again, sounds an awful lot like evolution).
>> Someone who believes there is a huge gap separating man from
>> apes should expect hundreds of genes in man that bear no
>> similarity to chimp genes.
> But is the gap to be found in the type of tasks genes do? If the
> answer is "no", then why should creationists expect to see a gap
RD: I don't understand your point here. Are you perhaps saying
RD: that the gap is caused by the presence of an immaterial spirit
RD: in man, rather than anything physical?
I'll also mention that the "IC requires ID" argument requires
the existence of such gaps. That's the whole point.