Early microblade assemblages in greater Beringia have been the focus of intense scrutiny because of their relevance to the problem of the peopling of the Americas. Although microblades have been produced in northeast Asia for more than 20,000 years, their manufacture is intensified in the terminal Pleistocene, coincident with the earliest definitive peopling of Beringia. In Alaska, where their manufacture was concentrated in the earliest Holocene period, microblades have often been viewed as diagnostic tools left by discrete ethnic groups (Na-Dene?) who followed the original (proto-Paleoindian?) migration. Alternatively, they have been viewed as a technology adapted for hunting in cold, northern environments, where lithics were relatively scarce, particularly in winter. A compromise view would suggest that such technologies were utilized in low frequencies by earlier populations, but became more prevalent as mammalian megafaunal extinctions took place, when caribou became of prime importance. The absence of such taxa to the south of the ice sheets might offer an alternative to ethnic arguments as an explanation of the limitations of expansion of microblade technologies into continental North America.