Re: Species [arbitrary to a degree]

[Graydon <graydon@dsl.ca>]

On Sat, Oct 20, 2001 at 12:08:48AM +0200, David Marjanovic scripsit:
> > > > A species is a population where there is no genetic restriction to the
> > > > degree of the common descent among the next generation from any member
> > > > of the species -- they can all mate effectively with each other, given
> > > > the opportunity.
> 
> BTW, I don't understand this formulation, apparently my English stops here.
> Can someone explain?

Since it was my formulation, I suppose I ought to try.

Since any individual organism belongs to _some_ species, by definition;
what we're talking about is how to detect the *edges* of a species.

Talking about that in population terms defines a species as a population
where, for any particular specific organism in the population, the
question is 'is there any restriction to the entry of genes from the
_other_ organisms being considered into the next generation of the
species to which we are sure this individual belongs'.  If the answer is
'no', then they're in the same species.  If the answer is 'yes', they're
not.  If the answer is 'not directly, but yes', we've got a more complex
situation, and one that won't arise in paleontology and can properly be
ignored in that context.

The edge is where (if!) the genes go into the future; damned hard to
detect in scattered fossils, although an indicative degree of variation
can be extracted from that.

-- 
                           graydon@dsl.ca
               To maintain the end is to uphold the means.