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Jhud -> RE: Evolution is inevitable (4/3/2008 11:21:33 AM)
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suspect that if they were isolated for long enough, the Vadoma would eventually become a separate species. (As you probably know, reproductive isolation is usually a requirement for speciation.) However, when speciation is made to happen as quickly as possible in a laboratory, it usually takes something like 50 generations; under non-ideal circumstances in nature it would probably take at least several hundred generations. Considering the length of the human reproductive cycle, that amounts to a minimum of ten thousand years of isolation for the Vadoma to become a new species, which isn’t likely to actually happen.
Actually, this would probably make a good test case; gene sequencing can give us an idea of how long the Vadoma have lived as a unique group, and how long ago the mutation which causes ectrodactyly arose in the population. Of course we are stuck with the literature which exists (which seems fairly meager in this case) so I am not sure this is a particularly good case to consider.
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What do you think of this example?
You know, I will readily admit it is probably one of the most robust examples out there, and presents some challenges to ID claims. While I have only gotten a chance to do a cursory reading of the literature, and will spend more time looking at it, my initial reaction is that this (and other examples like it that I know of) probably require some serious consideration by IDists.
However, in a number of respects I think it falls short of what I was looking for as definitive evidence for evolution. For one, the gene duplication and modification really only allows the langur to do more of what the langur family does already – digest leaves, though admittedly it in a significantly more efficient manner. So I am not sure it really represents the origin of a ‘novel’ functionality in the final estimation.
Also, as you admit, it really isn’t certain that this modification in anyway would prevent douc langurs from interbreeding with other Colobine monkeys. Obviously, the ability to exploit certain niches by the doucs itself encourages a separate breeding population, but not necessarily one that is following a unique evolutionary path.
And lastly, and perhaps most obviously, the duplication and subsequent modification of the homologous gene were thought to occur some 4 million years ago; that is evolution is in large part inferred. Perhaps I over looked it in the paper, but no real step-wise description of the accumulation of mutations to the gene seems to be given – instead, it seems to have happened relatively rapidly, in a nonrandom manner. This wouldn’t be a particularly Darwinian either process then either.
But I think it’s worth a longer look, which I will give it as I have time.
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Now, what I’m not sure of is whether what you’re demanding is that these mutations be observed actually happening in the present, but I hope you realize that’s probably an impossible standard of proof. Gene sequencing was not invented until 1975, and it’s only within the past decade or so that it’s been used to analyze the genomes of animals, which generally is not enough time for five separate beneficial mutations to cause the formation of a new species in nature. But the example I’ve given is still an example of what Behe is saying shouldn’t be possible: several separate mutations working together in order to produce a new function, which provides an advantage to the animal that has it.
Actually, there are a growing, and I might add, rather fascinating number of studies which are discussing the power of neofunctionalization, subfunctionalization, and the synthesis of those, subneofunctionalization. All are attempt to explain how it is that a duplication event would lead to either accumulated positive or negative mutations, both of which are possible, and whether or not what we are seeing isn’t instead derivation of ancestral genes which are being specialized and in some cases amplified. I think this is more likely under an ID paradigm.
A lot of this experimentation is based on observation, particularly of microbial organisms, whose ancestry is readily traceable.
It’s all quite new and preliminary, and driven in part by the failure of regular Neo-Darwinian theory to explain the development of life in many respects. I find it quite interesting and I am excited to see how it plays out.
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