Sea-level fall implicated in profound societal change about 2570 cal yr bp (620 bc) in western Pacific island groups

Abstract

During the warmest time of the last 10 000 years (Holocene Thermal Maximum), approximately 6000–4000 cal yr bp in the western Pacific, sea level is known to have reached as much as 2.1 m above its present mean level before declining subsequently. Records throughout the region show that sea level fell an average 0.7 m in the period 3500–2000 cal yr bp during which the earliest (culturally distinct) period of human occupation occurred in five western Pacific island groups [Bismarck Archipelago (Papua New Guinea), Fiji, Mariana Islands, New Caledonia, Vanuatu]. In the interest of testing whether there is evidence for climate forcing of cultural change in this region, dates are presented for the archaeologically conspicuous termination of early-period settlement in these island groups which show that it ended in each around 2570 cal yr bp. From the contemporaneity of this, it is argued that sea-level fall was the principal driver of this cultural transformation, forcing coastal peoples who had previously depended (largely) on foraging from nearshore-marine ecosystems to reconfigure their subsistence economy, something that invariably involved moving their settlements to places where horticulture and agriculture could be practiced more successfully. This research provides an example of where insights into causation of cultural change can be gleaned from comparing precise chronologies of human occupation to equally precise palaeoclimate chronologies.