RE: Species [arbitrary to a degree]

["Steve Brusatte" <dinoland@lycos.com>]

On Tue, 23 Oct 2001 07:20:49  
 Waylon Rowley wrote:

>       I can imagine a day in the future when
>paleontologists will scan fossil bones and form a kind
>of digital genome from the remains of the animal, then
>compare it with others. If you scanned modern animal
>bones and found a correlation between a certain amount
>of phenotypic change and BCS, then you would have the
>morphological equivalent, which could be applied to
>fossils. But then again, why not use the time
>machine??? 

Well, I suppose this could be very worthwhile, and is already begin done in one 
form (as HP Irmis said).  However, this too could be very equivocal.  I've 
always wondered what paleontologists would make out of dogs (Canis familiaris) 
if all they had to work with were the fossils.  Sure, all dogs have a similar 
skeletal structure and the same number of bones (I think), but the proportions 
(i.e. size and shape) vary between breeds, with something large (a Labrador, 
St. Bernard, etc.) having really heavy, large bones and something smaller (oh, 
a whippet or dachshund) having much smaller, lighter bones.  I'm not sure if 
the proportions remain relatively the same throughout the species.  I don't 
know enough about dogs.  But, I'm sure that it would take a considerable amount 
of time and effort before science grouped all domesticated dogs into one 
species, if all science had to go by was the bones. 

My point being this: using morphology to identify or define species may be fine 
in many cases.  However, that definition can be as equivocal as the "regularly 
reproduce in the wild" definition that HP Rowley gave.  Neither is a bad 
definition, but there are so many exceptions.  Species are arbitrary to a very 
large degree.  

Steve

**Disclaimer: the phenotypic variation in dogs is due almost entirely to human 
breeding, which is something that probably wouldn't be seen in nature (at least 
not to the degree that it is now).  However, it can still be used to prove a 
point.  Also, all domesticated dogs are very, very similar in anatomy, but some 
proportions do differ.


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