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Re: AW: Tawa hallae: everything you know about basal saurischians is wrong...



> I would be extremely skeptical about
> such an explanation.
> Lateral gene transfer is extremely poorly documented among
> Eukaryotes.
> 
> Moreover, that paper you cite (though I've only read the
> abstract), should not be interpreted too broadly.
> How confident are we that this putative "endogenous
> defective retrovirus" is actually of viral origin?
> Retrotransposons after all resemble retroviruses, but do not
> spread between species.
> 
> The abstract also notes: "Many mammalian viruses have
> acquired genes from their hosts during their evolution"
> 
> It is quite possible that this human gene in this
> "retrovirus" was incorporated into the genome of the virus,
> the virus integrates into the human genome, and the original
> copy is lost, leaving only the viral copy.
> No lateral gene transfer between species would have
> occurred.
> 
> Other possible explanations, are that the virus inserted,
> and then later a transposon stuck the gene in the middle of
> the virus.
> 
> Further more, feathers are multi-genic traits.
> The amino acid sequence is altered, many other genes (whose
> function I am not sure of), act to determine the shape of
> the scale (here, feathers being treated as modified
> scales).
> Feathers, and presumably this dino fuzz, originate from
> follicles, which will also require many genes to form, its
> not simply just weird protruding keratinized integumentary
> growth.
> 
> Given the similarity in structure and shape (long regular
> fibers), this fuzz presumably originates in follicles and
> has many genes acting to affect its shape, your hypothesis
> would require many many genes to be transported by a virus.
> I think the simpler explanation is just that they were
> ancestral or unrelated convergent evolution.

Of course. But incorporation of viral genetic code happens occasionally, and is 
certainly testable. I wouldn't propose a viral origin of feathers - if 
anything, a viral origin of that what transforms "scaly"/knobbly integument 
into filamentous structures, eventually to be fine-tuned to become feathers. 
But I wouldn't propose even that as a theory. It's merely one hypothesis, and 
not a likely one at that.

Yet it is a technically possible explanation, to be duly tested and refuted as 
soon as the underlying genetic structure is known well enough. Because it has 
far-reaching implications for the origin of archosaurian 
fuzz/pycnofibres/bristles if it is tested and can *not* be refuted.


Regards,

Eike

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