Re: Hierarchal vs Non-Hierarchal Interfaces to Biological Taxonomy

Bob Badour wrote:

Answering several distinct posts at once here...

> >>Which opens the floor to: "How many species did you have
> >>before B went extinct?"

One.

> > These kinds of questions are always interesting. And they
> > often lead me to the same conclusion, which is that
> > the concept being discussed is a construct of the
> > human mind, and not of the natural world. The
> > very idea of "species" is an abstraction. A useful
> > one, but an abstraction nonetheless.

Correct.

> Here's an even better one: Suppose a retrovirus comes along that conveys
> some fitness advantage so that it becomes ubiquitous among a species:
> ducks for instance. Suppose as well that the virus crosses over from the
> domesticated duck population into pigs and humans where it too becomes
> ubiquitous.
>
> At that point, humans, ducks and pigs all share a unique recent
> ancestor. Where does that put us in the taxonomy with ducks and pigs?

Your "at that point, humans, ducks and pigs all share a unique recent ancestor" is an incorrect premise. A percentage of the human genome (I want to say 8%, but I don't remember for sure) came from outside organisms like virii, but that doesn't make them our ancestors.

A facinating and related topic is mitochondria. There's evidence that it was orignally a separate organism that got incorporated into cells in a symbiotic relationship: cells provide the sugars that mitochondria need, and mitochondira provide the ATP that cells need. So a basic feature of eukariotic organisms (animals, plants and fungi) was acquired.

Larry Coon
University of California Received on Fri Dec 22 2006 - 18:19:00 CST