>Since erectus seemed to have crossed as far as Flores in Indonesia (an
>area which at the lowest Sea level during the Ice Age would have had a
>sea crossing of about 40km), some kind of sea raft or craft is implied.
> The construction of such a vessel would presumably imply language of
>some kind.
>
Lots of other animals have managed to cross similar water-barriers without
building rafts or having language. As a matter of fact pre-Homo sapiens
hominids seems to have had very limited ability to cross water gaps. The
only probable cases I am aware of are the Lesser Sundas (as far as Flores)
and Corsica-Sardinia. These may well be cases of sweepstake dispersal.
By the way, different palaeolithic Homo sapiens populations seem to have
had remarkably different nautical abilities. In Melanesia they got as far
as the Manus, which means crossing 300 km of open sea, while most
mediterranean islands weren't colonized until early Holocene and the
Tasmanians apparently never reached King or Flinders Island (which are
clearly visible from Tasmania) in 12,000 years.
Tommy