Sea-crossings capacities and opportunities during prehistory: Survey and
comparison between Homo species

Jean-Marie Hombert & Christophe Coupé
Laboratoire Dynamique du Langage, CNRS a Université Lyon 2, Lyon, France

Jean-Marie.Hombert@univ-lyon2.fr

First sea-crossings during prehistory can be considered as tangible
clues of a sophisticated communicative system, along with other
behaviours such as ritual burials or art production.  This conclusion
can be drawn either from the technological capacities required to build
rafts (Davidson & Noble 1992) or the planification and motivation
necessary to undertake dangerous sea-crossings over large sea gaps
(Hombert & Coupé 2002).  The best known and studied example of distant
sea-crossings is the one involved in the colonization of Australia by
Homo sapiens around 60,000 years ago. 

If modern behaviours become numerous at the beginning of the Upper
Palaeolithic and the so-called Cultural Explosion at around 50,000 BP,
scholars argue about the existence of such behaviours in earlier Homo
sapiens (d’Errico & al 2001), and even more in earlier representatives
of the Homo gender.  Relations between language and tools, early
sepultures or clues of a symbolic thought can all be discussed and put
into question because of possible misinterpretations of the data.  In
this context, the distant colonization of Australia around 60,000 years
ago already antedates the former limit of 50,000 years, but
identification of possible earlier sea-crossings is valuable to better
assess the emergence of modern behaviours, and consequently the
development of human language. 

To this end, we try to survey the possible regions on the planet where
sea-crossings may have occurred during the last million of years: the
Wallacea region between south-eastern Asia and Australia / New Guinea,
the Gibraltar Strait and the islands of the Mediterranean Sea, the
Southern and South-eastern coastlines of Asia, the Eastern coastline of
Africa.  Computations of visibility between an observation point and a
target location and evolutions of the sea level are taken into account
to determine which locations could had been populated by sea-crossings
with or without visibility, or on foot during a period of lower
sea-levels. 

The on-going measurements reveal that many locations, including Japan or
islands in the Mediterranean Sea were reachable on foot during several
periods of the Pleistocene.  The Andaman Islands are demonstrated to
represent another example of Homo sapiens’ sea crossings with
visibility, having possibly occurred before the colonization of
Australia.  The only example of Homo erectus’ sea-crossings seems to
occur in the Wallacea region, where sites discovered in the island of
Flores prove that Homo erectus had managed to cross a sea gap of around
twenty kilometres more than 700,000 years ago (Morwood 2001) (Bednarick
1997).  The possible crossings of the Gilbratar Strait, with presence of
Homo sapiens in Northern Africa and Homo neandertalensis in today’s
Spain at the end of the Middle Palaeolithic also raise challenging
questions about the interactions between these two species (Hublin
1992). 
 
On the basis of these conclusions, we discuss sea-crossings as a
cultural behaviour which appeared early in some human groups, and a
possible cultural difference between Homo sapiens and earlier human
species based on a greater inclination towards novelty seeking and
discovery in Homo sapiens.