A recently published archaeological sequence supported by information from six sites excavated in the Mangarevan group in 1959 is summarized in the context of additional data and current interpretations of the prehistory of southeastern Polynesia. The known part of the Mangareva sequence covers the period from ca. a.d. 1200 to the time of early nineteenth-century contact with Europeans, with its datingen hanced by four new radiocarbon age determinations plus four previous ones, all on samples collected in 1959. More recent information from archaeological investigations on nearby Pitcairn and Henderson islands, showing they formed part of a long-term interaction sphere with Mangareva, indicate that while the early part of the Mangareva sequence from ca. a.d. 800–1200 remains undocumented, buried cultural deposits for this interval probably exist within Rikitea village on the main island of Mangareva. An a.d. 700–800 settlement for the Mangareva group is consistent with a similar age and origin for the first inhabitants of Easter Island, as aspects of the thirteenthcentury assemblages from both places are comparable. A similar age is also supported by several dates for an initial colonization of Henderson Island in this period. Recent linguistic reworkingof the early subgroupingof Eastern Polynesian suggests Easter Island, Original Mangarevan, and probably the extinct Polynesian languages of Henderson and Pitcairn were the first in the region, placing the age of that subgroup around a.d. 700–800. A major secondary contact with Marquesan speakers who may have settled in Mangareva at a.d. 1100–1300, seems to have been the basis for changing it into a Marquesic language, of a form then taken to Rapa. The archaeology, biological relationships, and linguistic history of the region now provides a robust and consistent outline for the geographic expansion into Southeast Polynesia.