Environmental setting of human migrations in the circum‐Pacific region

Aim  To assess the genetic and archaeological evidence for the migration of modern humans out of Africa to the circum-Pacific region and compare the migration patterns with Late Pleistocene and Holocene changes in sea level and climate. Location  Southern and eastern Asia, Australia, and Oceania. Methods  Review of the literature and detailed compilations of data on early human settlements, sea level, and climate change. Results  The expansion of modern humans out of Africa, following a coastal route into southern Asia, was initially thwarted by a series of large and abrupt environmental changes. A period of relatively stable climate and sea level from c. 45,000 yr bp to 40,000 yr bp supported a rapid coastal expansion of modern humans throughout much of Southeast Asia, enabling them to reach the coasts of northeast Russia and Japan by 38,000–37,000 yr bp. Further northwards, migrations were delayed by cold northern climates, which began to deteriorate rapidly after 33,000 yr bp. Human migrations along the coast of the Bering Sea into the New World appear to have occurred much later, c. 14,000 yr bp, probably by people from central Asia who were better adapted to cold northern climates. Cold, dry climates and rapidly changing sea levels leading into and out of the Last Glacial Maximum inhibited coastal settlement, and many of the sites occupied prior to 33,000 yr bp were abandoned. After 16,000 yr bp, the sea-level rise slowed enough to permit coastal ecosystems to develop and coasts to be re-colonized, but abrupt changes in climate and sea level inhibited this development until after 12,000 yr bp. Between 12,000 yr bp and 7000 yr bp there was a dramatic increase in reef and estuary/lagoon ecosystems, concurrent with a major expansion of coastal settlements. This early Holocene increase in coastal environments and the concomitant expansion of human coastal-resource exploitation were followed by corresponding declines in both phenomena in the mid-Holocene, c. 6000–4000 yr bp. This decline in coastal resources is linked to the drop in sea level throughout the Pacific, which may have caused the widespread population dislocations that ultimately led to the human expansion throughout Oceania. Main conclusions  Climate and sea-level changes played a central role in the peopling of the circum-Pacific region.