48
3 The Oceanographic Context
Between 7,000 and 5,000 years ago, as a possible long-term consequence of
the tectonic disturbances that followed the last Ice Age flood, undersea volcanic
activity in the West Pacific Warm Pool led to an astonishing increase in SSTs within
the Warm Pool between the Spice Islands and Japan. As early as the 1970s the
pioneering climate historian H.H. Lamb [13] noted that
Examination of corals and mollusk shells on raised beaches in Japan, radiocarbon dated
7000 to 5000 years ago, suggests (Taira 1975) that the Kuro Shiwo (warm North Pacific
Current) had about the same northward extent as today but was between 2 and 8 ◦ C warmer
than today. The smaller values of water temperature anomaly were apparently derived by
species examination, the larger values by oxygen isotope measurement – a middle value
of 5 ◦ C warmer than today may be realistic. Crustal movements in Japan and further south
are suggested by Taira as partly the cause of the subsequent change of the current and
the prevailing temperatures in it, since the supposed explanation is that the warm water
current reaching Japan in the warmest postglacial times was drawn from farther south, from
the ocean areas just north of Papua New Guinea that are still the warmest in the world –
present-day mean 29–30 ◦ C.
Geoffrey Irwin’s concept of a safe “voyaging nursery” in the cyclone-free corridor between the north coast of New Guinea and the Bismarcks and Solomons has
received considerable attention. His idea is of a voyaging nursery which promoted
the early evolution of the maritime skills and technologies needed for the Lapita
peoples’ exploration and colonization of the Pacific [14]. Atholl Anderson [15] has
challenged this concept, arguing that there are other cyclone-free areas to the west
which might have been equally useful and that “small-craft sailors adapt quite easily to predictable cyclone seasonality”. But Irwin’s concept of a voyaging nursery
can be defended even if the area he delineates for the nursery may be harder to
defend. As mentioned in the Introduction, we propose an earlier and far more extensive voyaging nursery, the WPWP stretching north from the Spice Islands through
Micronesia towards Japan. This area is unique. Its most remarkable characteristic is
not that it is cyclone-free but that it possesses the warmest ocean waters in the world
and that at some time between 7,000 and 5,000 years ago its SST was perhaps as
high as 35 ◦ C.
Higher SSTs in the WPWP allowed long-distance voyaging in exposed sailing
rafts with less risk of death from hypothermia for their crews. Volcanically heated
waters provided a voyaging nursery in which long-distance voyaging on bamboo
rafts was safer than it would have been anywhere else in the world, perhaps at
any time. Extraordinarily high SSTs provided a safety net as well as the impetus and opportunity to develop skills relevant to both long-distance trading and
ocean voyaging. And they provided the opportunity, through the impetus of longdistance voyaging, for Spice Islanders to genetically acquire the further level of
cold adaptation needed for it to be physiologically possible for them later to extend
long-distance voyaging into the cooler waters of the Indian and Pacific Oceans.
Favourable conditions in the West Pacific Warm Pool seem also to have prompted
experimentation leading to the development of ocean-going double-outriggers and
perhaps further experimentation in the use of sail. Combined, improved maritime
skills and a higher level of cold resistance, following experience in the West Pacific
3 The Oceanographic Context
Between 7,000 and 5,000 years ago, as a possible long-term consequence of
the tectonic disturbances that followed the last Ice Age flood, undersea volcanic
activity in the West Pacific Warm Pool led to an astonishing increase in SSTs within
the Warm Pool between the Spice Islands and Japan. As early as the 1970s the
pioneering climate historian H.H. Lamb [13] noted that
Examination of corals and mollusk shells on raised beaches in Japan, radiocarbon dated
7000 to 5000 years ago, suggests (Taira 1975) that the Kuro Shiwo (warm North Pacific
Current) had about the same northward extent as today but was between 2 and 8 ◦ C warmer
than today. The smaller values of water temperature anomaly were apparently derived by
species examination, the larger values by oxygen isotope measurement – a middle value
of 5 ◦ C warmer than today may be realistic. Crustal movements in Japan and further south
are suggested by Taira as partly the cause of the subsequent change of the current and
the prevailing temperatures in it, since the supposed explanation is that the warm water
current reaching Japan in the warmest postglacial times was drawn from farther south, from
the ocean areas just north of Papua New Guinea that are still the warmest in the world –
present-day mean 29–30 ◦ C.
Geoffrey Irwin’s concept of a safe “voyaging nursery” in the cyclone-free corridor between the north coast of New Guinea and the Bismarcks and Solomons has
received considerable attention. His idea is of a voyaging nursery which promoted
the early evolution of the maritime skills and technologies needed for the Lapita
peoples’ exploration and colonization of the Pacific [14]. Atholl Anderson [15] has
challenged this concept, arguing that there are other cyclone-free areas to the west
which might have been equally useful and that “small-craft sailors adapt quite easily to predictable cyclone seasonality”. But Irwin’s concept of a voyaging nursery
can be defended even if the area he delineates for the nursery may be harder to
defend. As mentioned in the Introduction, we propose an earlier and far more extensive voyaging nursery, the WPWP stretching north from the Spice Islands through
Micronesia towards Japan. This area is unique. Its most remarkable characteristic is
not that it is cyclone-free but that it possesses the warmest ocean waters in the world
and that at some time between 7,000 and 5,000 years ago its SST was perhaps as
high as 35 ◦ C.
Higher SSTs in the WPWP allowed long-distance voyaging in exposed sailing
rafts with less risk of death from hypothermia for their crews. Volcanically heated
waters provided a voyaging nursery in which long-distance voyaging on bamboo
rafts was safer than it would have been anywhere else in the world, perhaps at
any time. Extraordinarily high SSTs provided a safety net as well as the impetus and opportunity to develop skills relevant to both long-distance trading and
ocean voyaging. And they provided the opportunity, through the impetus of longdistance voyaging, for Spice Islanders to genetically acquire the further level of
cold adaptation needed for it to be physiologically possible for them later to extend
long-distance voyaging into the cooler waters of the Indian and Pacific Oceans.
Favourable conditions in the West Pacific Warm Pool seem also to have prompted
experimentation leading to the development of ocean-going double-outriggers and
perhaps further experimentation in the use of sail. Combined, improved maritime
skills and a higher level of cold resistance, following experience in the West Pacific