Iain,
Even though it's fairly easy to explain in biochemical and genetic
terms ("no big deal"), I would call a chromosome rearrangement (like a
chromosome fusion) a macroevolutionary event. Speciation is often the
end result of such rearrangements because of their impact on meiosis.
I would also call it non-Darwinian and non-gradualistic. Genetically,
it is a macromutation (perhaps even of the Goldschmidt hopeful monster
variety).
Dennis has rightly explained how such a thing can be propagated and
fixed in a population. Interestingly, a comparison of mammalian
genomes suggest that much of the original mammalian radiation and
subsequent diversification is accompanied by such chromosome
rearrangements. It may well be that the chromosome rearrangement (with
subsequent selection) are the cause of such diversification.
TG
On Jul 20, 2009, at 11:43 AM, Iain Strachan wrote:
>
>
> On Mon, Jul 20, 2009 at 6:17 PM, Dehler, Bernie<bernie.dehler@intel.com
> > wrote:
>> Moorad said:
>> "For one, we can make all sorts of predictions in our theory of
>> gravitation and test them experimentally, witness Apollo 11,
>> whereas the same cannot be said of evolution."
>>
>> I think this is false. We can test evolutionary theory. A
>> macroevolutionary hypothesis is that man descended from an apelike
>> creature. Can it be disproven? Yes. Rather than running
>> experiments, instead data is collected. Genomic studies. Data
>> falls in line with evolutionary theory, and helps define/refine
>> evolutionary theory. Data also disproves creation of human by fiat
>> or any kind of sudden, non-descent (YEC/OEC idea of human creation).
>
>
> No it doesn't. Or at least your favoured chromosome fusion example
> doesn't. Now before you have a go at me about what I believe, I'll
> state right at the start that I believe in the reasonable hypothesis
> that apes and humans are descended from an ape-like ancestor that had
> 48 chromosomes. I imagine it's possible to date (using genetic drift)
> the time in history when the fusion occurred and that will verify it
> was before humans came along. But I believe in long time-scales;
> YEC's don't.
>
> However, as we have seen from Dennis's explanation and the quote from
> Darryl Falk, it seems the chromosome fusion is no big deal - it is a
> microevolutionary step in itself that doesn't change the genetic
> material. A heterozygous 47 chromosome (23+24) individual can mate
> perfectly well with a 48 or a 46, and meiotic drive ensures the 46
> individuals eventually take over the population.
>
> Hence, a YEC could well argue that man and apes were created
> separately, and the humans originally had 48 chromosomes.
>
> You'll need a lot more than evidence of a chromosome fusion to
> disprove that assertion.
>
> Iain
>
>
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Terry M. Gray, Ph.D.
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Colorado State University
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Received on Mon Jul 20 18:14:19 2009
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