Re: Trogons and Grebes

["Jaime A. Headden" <qilongia@yahoo.com>]

David Marjanovic (david.marjanovic@gmx.at) wrote:

<As reported, even molecular divergence date estimates say they're too old for
that. :-)>

  Whew! And here I thought that if the fossil data supported a relationship, it
was relatively strong! After all, it tells us dinosaurs are bird ancestors! I
guess molecular divergences that keep changing are stronger data, no? 

  Seriously, though: We cannot hold that because molecular divergence dates say
otherwise, the gross anatomical similarities are therefore discounted. Even
though hindlimb modifications may be functionally convergent due to a similar
locomotor strategy, as in hesperornithiforms, this doesn't neccessarily
discount their usefulness in a phylogenetic analysis, as Tim alluded to,
because they are still essentially products of evolutionary and therefore
genetic history and may very well have had a shared common ancestor with the
same locomotor strategy that, in 50+ million years of time, can have been
modified to produce the modern variances. Not that I am arguing this is true,
but there is caution in "believing" in molecular distance when it changes
depending on the locus you use. Different genes, different DNA, different
dates. Recent studies in human history even argue for a hybridization event in
hominoids. Not hominids, but hominOIDS, that produce variation and eventual
merging of disparate genetic lineages up to the australopithecine divergence,
but perhaps including them as descendant from this hybrid-event. I think dating
based on just apparently plastic outputs is WEAK, and needs to be combined with
all other variations and dates as an added piece of info in history, but in the
end, I do not think it gives us the ability to determine the age of any event
... yet.

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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