[Taxacom] Molecules vs Morphology‏

[John Grehan]

Scott, go and have a nice cuppa tea.
 
John Grehan

________________________________

From: Scott Fisher [mailto:scottfisher2010 at yahoo.com] 
Sent: Monday, August 17, 2009 11:31 PM
To: John Grehan; Taxacom
Subject: Re: [Taxacom] Molecules vs Morphology‏


Please honor the following promise:


"I have had a good number of years of interesting discussions, but legal threats are not something I want to contend with. This is my last posting.




John Grehan"




Thank you,




SF


________________________________

From: John Grehan <jgrehan at sciencebuff.org>
To: Taxacom <taxacom at mailman.nhm.ku.edu>
Sent: Sunday, August 16, 2009 9:50:31 PM
Subject: Re: [Taxacom] Molecules vs Morphology‏


-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Jason Mate
Sent: Sunday, August 16, 2009 6:54 PM
To: Taxacom
Subject: Re: [Taxacom] Molecules vs Morphology‏

> OK, third attempt, why do you speak of false and true instead of congruent 
> and incongruent? Do you have access to the truth?

Because that was the way others phrased their interpretation.


> > Because if it is then there is nothing to compare. 

Not in the sense of falsification of one or the other.


> Do your results have no bearing upon the relationships of Homo, Pan & Co.?
> If it neither supports nor contradicts, one must ask, is there any 
> phylogenetic signal?

Obviously my results contradict molecular results. 

> Yes, but a large number of similarities vs a large number of uniquely shard similarities are two different things.

> John, more information is better than less information. 

If its more of the right kind of information. More similarities is fine if, in my opinion, they can be shown to be uniquely shared within the in-group.

> Or do morphologists stop looking once they have found one character? Come
>  on, stop seeing the conspiracy in every statement. 

?????

> Secondly, the title of "uniquely shared similarities" hints at, "I 
> understand these characters but not those". 

????

> A priori you shouldn´t determine which are and which are not uniquely 
> shared.

On that I happen to disagree. It is my understanding of cladistic methodology is that one restricts analysis to those features that are unique to the in-group (or at least so rare in the outgroup that one has some confidence in their being derived). To do that one must identify which features meet that criterion. The analysis is only to determine which group of relationships suggested by those features is best supported.

And as for unique, one of the reasons why morphology is less homoplasious than molecular data is simply the character selection process in the former. In the latter you can´t say "we dumped 80% of the variable positions because they were too variable". Also most mutations at the gene level are more or less neutral which helps when you reconstruct a phylogeny.

> > However, if I have 50 genes, both nuclear and mitochondrial, and 
> > they point one way, and the morphological data is in conflict... 
> > lets just say the morphological dataset needs some explaining.

>Or viceversa

If you are objective, no.

Right. That is my point, it could be either way. The assumption has been that the morphological results need 'explaining' as if the incongruent molecular results do not.

John Grehan


Best  

Jason


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