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Re: Endothermy, UCP1 gene deletion, and the origin of birds



> In his new paper Stuart A. Newman
> offers an interesting, if unclearly stated, hypothesis of
> bird origins. He proposes that it could have occurred due to
> the loss of the mitochondrial gene UCP1

First and most obvious question: expression profile of UCP1 in crocs, squamates 
and frogs? (Apparently unknown at present)

If we learned anything from the "aggression gene"  and the "gay gene" and the 
"monogamy gene" (which were refuted when evolutionary aspects were considered, 
if not earlier), it would be nice if people stopped publicly speculating about 
the evolutionary role of this or that gene. That was OK in the 1980s, but by 
now there are ways to actually study such questions rather than to merely 
ponder them. And by now there are places for speculation other than scientific 
journals.

Newman may have a point, but it's not even a hypothesis. For a hypothesis you 
need actual data, not some vague notion. And actual data is apparently what's 
lacking here. UCP1 is ubiquitious in vertebrates - it obviously evolved in 
poikilotherms (it may be very old, as the UCP family is even found in plants). 
What was its function there? Nobody seems to know at present, or at least I did 
a quick lookup and couldn't even find an expression profile for _Xenopus_. And 
for all we can say, IF avUCP (avian UCP) is not the functional equivalent of 
UCP1 in birds, UCP1 is not as crucail as it might look (which is also supported 
by 
http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.0020129).

What we can definitely say is that UCP1 is not "the brown fat gene" or "the 
thermoregulation gene" - if anything, that's what *mammal* ancestors co-opted 
it for.

Essentially, we're still stuck at 
http://www.springerlink.com/content/7275607621356t7g/ and 
http://www.sciencedirect.com/science/article/pii/S0005272808000480 (and for a 
more recent summary, see 
http://people.usd.edu/~dlswanso/Pubs/Swanson%202010%20Current%20Ornithology.pdf)

If one is not a prima facie geneticist and talks to people who are, the 
question "what's your taxon?" can work wonders. Molecular genetics has still 
such a high input(funding/time)/output ratio that most researchers can't afford 
to look beyond the scope of one or very few species. In other words, their 
results are often barely significant from an evolutionary perspective, but they 
don't tell you that because usually they don't realize it themselves. 
My favorite term in genetics is "the mouse"; I have a habit of asking back 
"what mouse? The Common Fat Mouse (_Steatomys pratensis_)?" (a nesomyid, and 
thus doubtfully closer to _Mus musculus_ than any hamster or lemming) 
Alternatively, one can use _Akodon iniscatus_.


Regards,

Eike