Hi Andrew, I wasn't suggesting that two species could never prodice fertile hybrids, but only that the inability to produce fertile hybrids, when present, is certain proof of specific distinctness, since a single species incapable of producing fertile offspring would soon be extinct. Regards, Paul M. > Well, fertility of hybrids is not a test of specific distinctness. I > believe there is a fertile mule known... > -- > Andrew Grebneff > 165 Evans St, Dunedin 9001, New Zealand > <[log in to unmask]> > Seashell, Macintosh, VW/Toyota van nut > >