I agree with Piotr, just some
comments on "habilis".
For discussions of fossil hominids, there are
better places IMO, eg, http://www.egroups.com/group/paleoanthropology.
I only want to say that the term H.habilis is used in different ways in
popular books & in scientific papers. The famous fossil skull KNM-ER-1470
(with a brain size of ca.770 cc & with its supposed "speech
centres" in its endocast, perhaps even some area of Broca) is nowadays not
included in habilis but usu. in rudolfensis. The species
habilis sensu stricto (eg, KNM-ER-1813 or OH-62) is today often
included in the genus Australopithecus, and some even think that
fossils like KNM-ER-1470 should not be included in Homo, but should be
considered as some sort of large-brained robust australopithecine. So it's by no
means certain that habilis was an ancestor of ours. H.erectus
OTOH was probably very close to our ancestors.
Very probably there existed once a single Proto-World language
at the time of the Last Common Ancestor of all living humans (sapiens),
just before they first split into different groups (ca.150,000 years ago?),
though we may never see this language reconstructed. Very probably the
sapiens LCA ca.150,000 ya had some sort of grammaticised language.
Probably our species is derived from erectus/ergaster, but whether
these creatures already had some sort of speech (with or without grammar) is
very doubtful. We're discussing these things & speech origins at http://www.onelist.com/community/AAT.
Very interesting but very speculative. That's no problem as long as you know
that you're speculating.
Marc