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Re: the tonight show
I hope you are right, that what you said below is what George really
meant. It would certainly be an improvement. However, I still wouldn't
completely agree even with that, because you are still assuming C and E are
the same evolutionary distance from A, which isn't necessarily so. If C is
a modern Galliform, and E is a modern Blue Jay, there are almost certainly
more intermediate forms on the line between B (Hesperornithiform or
Ichthyornithiform) and the blue jay than between B and the galliform (not to
mention that the intermediate forms leading to the blue jay would probably
also have somewhat greater evolutionary distance between each form).
That's what tends to happen in lineages that are evolving more
rapidly. But Galliforms are more bradytelic and conservative. Just like
the cyanobacteria of today are far more closely related to any of the
cyanobacteria living billions of years of ago than they are related to other
modern bacteria. Cyanobacteria are the epitomy of brachytely. Their
"offramp" is billions of years long chronologically, but very short in
And regarding Jaime's post tonight, I reiterate that Charles Darwin
did say that classification should reflect both phylogeny AND evolutionary
distance, and if I can't find the quotes tonight, I'll try to post them
tomorrow. He clearly stated this at least two different times in "The
Origin of Species". In elegant 19th Century prose, he says that sister
groups that have evolved at greatly different rates should be at different
taxonomic ranks in classifications. In so many words he was advocating the
use of paraphyletic groups when necessary. I look it up and you can read
for yourselves tomorrow.
Subject: Re: the tonight show
Date: Wed, 10 Jan 2001 19:58:18 EST
In a message dated 1/10/01 3:05:40 AM Eastern Standard Time,
> > All modern birds are equally closely related to Velociraptor, since
> > share the same most recent common ancestor. That is, the common
> > any modern bird and Velociraptor is the same species as the common
> > of any other modern bird and Velociraptor.
> Is this correct? Consider four creatures, A, B, C, and D.
> A --> B --> C
> A --> D
> Both C and D have A as their most recent common ancestor, but because B
> interceded, C may, or may not, be more closely related to A than D.
But George was referring to this situation:
A --> B --> C, E
A --> D
C and E represent modern birds in George's statement, and D represents
_Velociraptor_. C and E are equally closely related to D, since the most
recent common ancestor of C and D is A and the most recent common ancestor
E and D is also A.
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