Re: Hierarchal vs Non-Hierarchal Interfaces to Biological Taxonomy

Bob Badour wrote:

> Do you think donkeys and horses are the same species? Or does the
> reasoning that leads to "one" above lead to "two" for them?

I don't think there is a universal definition for species. Remember, the taxonomies are organizational conveniences, and as someone else said, nature is too subtle to fit cleanly within our systems.

In general, we differentiate species on the basis of: 1) Typology (conforming to a set of fixed characteristics); 2) Morphometry (essentially the way they look. IE, some organisms can look very similar without being closely related);
3) Sexual isolation (this gets to your question about hybrids like mules. In most cases, the hybrids are sterile, so they do not challenge this criterion). 4) Phylogeny -- members of a species have a common ancestor.

> What is the definition of ancestor that excludes them?

There is no phylogenic relationship, for one.

> Agreed. Are you familiar with Aubrey de Grey's theory of mitochondrial
> aging?

No. (Admittedly this isn't my field, so my knowledge only goes so far -- and I had to look up the part above about species). I'm a computer scientist who happens to have an interest in all science. It sounds like Paul is much better qualified to discuss these topics than I.)

Larry Coon
University of California Received on Sun Dec 24 2006 - 11:12:04 CST