Hi all,

As a birder (and a chemist), I find this all quite interesting.  However, I 
have to ask this question: isn't the separation of bird species by 
differences in their DNA kind of "arbitrary"?  It's all decided by some 
group of scientists that decided that species differentiation occurs when 
there are x% difference in the DNA of two species, but this x% was decided 
by people and not by some test that isn't subject to a person making the 
"differentiation limit".  For example, this group of scientists may have 
decided x is 10%, so if two birds difffer in their DNA by 10%, they are 
different species.  But who is to say it's really 10%?  That's the problem I 
have with all this, it's too arbitrary.

Let em also ask this:  what is the % difference in the DNA of two individual 
humans that are not "related"?

Good birding,
Richard


>>
>>
>>
>The bar codes are a good indication, though, even if you might not want to 
>treat them as definitive.  The bar code consists of 648 base pairs, many of 
>which might vary from species to species and some of which vary even inside 
>a single species.  The variation might not change the corresponding protein 
>at all, it might not vary the protein in a way that changes its function, 
>or it might vary the function in ways that improve its fitness under the 
>conditions of the habitat of varying species.  The variations that don't 
>change the protein at all are especially interesting since they are 
>necessarily not subject to selection and so tend to occur in proportion to 
>the amount of time since the species involved stopped interbreeding.  If 
>all organisms had exactly the same protein, the variation in base pairs 
>would be especially useful.
>
>For whatever it may be worth, the web page for the organization which will 
>store this data indicates that different species generally differ in at 
>least 5% of the base pairs.
>
>The problem is using the data is an old one: how long must two populations 
>be separated before they should be regarded as separate species?  What is 
>the criterion for separate anyway?
>
>What I find interesting for birdwatchers in this data that has been 
>distinctly underemphasized is that the number of potential splits is 
>roughly equal to the number of potential lumps.  Have we reached some kind 
>of temporary equilibrium in the number of bird species?
>
>--
>Maurice Barnhill   [Use ReplyTo, not From]
>[bellatlantic.net is reserved for spam only]
>Department of Physics and Astronomy
>University of Delaware
>Newark, DE 19716

_________________________________________________________________
Don’t miss your chance to WIN 10 hours of private jet travel from Microsoft® 
Office Live http://clk.atdmt.com/MRT/go/mcrssaub0540002499mrt/direct/01/