Ha, ha, even paleontologists can't agree.  Many of the newly discovered finds such as Mungo Man are being given a joint billing i.e containing features of "both" Australopithecines and Homo whatever. Paleontologists then select which camp they wish to align themselves with (that usually coincides with the focus of their research grants). 
 
Gerry
 
----- Original Message -----
From: Richard Wordingham <richard.wordingham@...>
To: Nostratica@yahoogroups.com
Sent: Friday, February 21, 2003 3:37 PM
Subject: [Nostratica] Re: Proto-Celtic

I think this is a question for
palaeontologists rather than
linguists.  While it does happen in
biology, I think the only instances
in language occur when a language
becomes a 'classical' language,
such as French and Latin.  Even
then, Mediaeval Latin did have its
own innovations.
Richard.