The region of modern Senegal was a part of the larger region called Upper Guinea by European traders. In the absence of written sources and monumental ruins in this region, the history of the early centuries of the modern era must be based primarily on archaeological excavations, the writing of early geographers and travelers, written in Arabic and data derived from oral tradition. Combining these data suggests that Senegal was first populated from the north and east in several waves of migration, the last being that of the Wolof, the Fulani and the Serer. Africanist historian Donald R. Wright suggests that Senegambian place-names indicate "that the earliest inhabitants might be identified most closely with one of several related groups—Bainunk, Kasanga, Beafada... To these were added Serer, who moved southward during the first millennium A.D. from the Senegal River valley, and Mande-speaking peoples, who arrived later still from the east." Probable descendants of Bafours were pushed southward by the Berber dynasty of Almoravids.