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Re: the tonight show




Nick,
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 evolutionary distance.
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.
------Ken
********************************************************
From: NJPharris@aol.com
Reply-To: NJPharris@aol.com
To: dinosaur@usc.edu
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, wuckus@ecol.net
writes:


> > All modern birds are equally closely related to Velociraptor, since they
> > share the same most recent common ancestor. That is, the common ancestor
> of
> > any modern bird and Velociraptor is the same species as the common
> ancestor
> > of any other modern bird and Velociraptor.
>
> Is this correct? Consider four creatures, A, B, C, and D.
>
> A --> B --> C
>
> and
>
> 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 of
E and D is also A.


--Nick
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