The majority of archeological work in Micronesia has occurred in the last 5 years. Prehistoric peoples moved into this area from two separate areas—insular southeast Asia and eastern Melanesia. The high islands of western Micronesia were settled at least 4000 years ago. Settlement in eastern Micronesia occurred at least 2000 years ago. On high islands, complex, stratified societies developed, each with distinctive material remains. Atolls have proved to be significant sources of archeological materials and figure prominently in the prehistory of the area.