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gluadys -> RE: genetic evidence against evolution (6/2/2008 1:37:38 PM)
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quote:
ORIGINAL: Jhud
Now it seems to indicate that the genetics of previous generation is indeed present in modern ones, and so would establish the reality of common descent – but common descent itself isn’t a mechanism, it would be an after the fact reality.
And that is the point. It establishes common descent. And you are right. Other than in cases where we have observed it in real time, we can only establish common descent after the fact, through evidence such as ERVs.
Now as to mechanism, I think you are omitting that selection is a mechanism of evolution and selection is principally a matter of differential reproductive success. So I would not say that reproduction is never a mechanism of evolution.
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ERVs tell us nothing of the how organisms came to be different from one another in terms of the complex interdependent and independent genetics that are the basis for their various structures and systems.
ERVs per se don't, but cladistic speciation and subsequent innovation and selection in the separated gene pools does tell us how organisms came to be different from one another.
Again, you don't seem to count this as a mechanism, but it is certainly a mechanism of population genetics and generation of biodiversity.
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Now a question; why is it we couldn’t simply assume that ERVs infected the same places in the genome across a number of different similar organisms?
Well, first you have to consider that we are dealing with an incredibly small subset of viral infections. 1. They are failed infections---ones that did not succeed in taking over the cellular reproductive machinery to create new viruses.
2. They are viral infections of germ-line cells only, and within that subset, only of germline cells which are active participants in a successful conception.
3. The organism which first inherits the ERV must then bequeathe it to all of some subsequent generation of its species.
Second, one has to consider the vast number of loci at which a viral infection could be situated. Even allowing for "hot spots" which seem to attract more than their fair share of such infections, there are billions of possible loci. That two viruses acting independently would hit the same spot is therefore highly remote under any circumstances. That both of them would do so in a germline cell which is eventually the common ancestor of the whole species constitutes a probability close to zero.
In addition, that both infections would leave identical signatures is extremely unlikely. Each viral infection is unique even when it is the same virus in the same species. So even if both became ERVs, it is highly improbable that they would be identical, even in the extremely remote possibility that they might occur in the same locus.
Finally, that the ERVs shared across species would conform to the same phylogenetic pattern as determined by cladisitic analysis makes no sense at all without common descent. Identical ERVs occurring independently could and should show up in orangutans and humans without also showing up in gorillas and chimpanzees.
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