Re: Of Tarbosaurs and tabbies

[zone65@bigpond.com]

On Thursday, March 18, 2004, at 12:35  AM, Thomas R. Holtz, Jr. wrote:

> > From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf 
> > Of
> > zone65@bigpond.com
> >
> > I should know this already, but when did the lion and tiger diverge?
> > Would it be accurate to say they are each branches of the same species
> > on the path to distinct speciation? If so, do they therefore represent
> > transitional forms, of the type so coveted in the fossil record?
>
> No, lions and tigers are about as secure as species as any two taxa 
> are. It
> is fairer to say that these are two distinct species in which genetic 
> or
> morphological features to prevent interbreeding have not evolved.

OK, but doesn't that really amount to them being in the incomplete 
process of diverging from each other? Shouldn't they only become 
distinct species when they can no longer interbreed at all? Currently 
they can still do so, but the results are inconsistent, and will 
presumably eventually amount to nothing when they've evolved away from 
one another sufficiently.

> As Darwin
> showed, regional varieties grade into subspecies which grade into 
> species:
> there aren't distinct breaks between these "ranks".

I suppose really every critter is a transition from one thing to 
another. I do think "species" has been assigned all too readily, but it 
seems we're moving away from that - good to see.

Peter Markmann