Scholars in the fields of history, linguistics and comparative religion have challenged the conventional view that America is a time capsule of Palaeolithic culture. Most notably, historian Ethel Stewart (1904- 2002) suggested more recent Asian origins for some American Indian languages and religions. Xi-Xia, a Northeast Tibetan kingdom, fell to Genghis Khan in 1227. Orthodox history maintains that the men were slaughtered and the women enslaved. Stewart, however, argued that the warriors of Xia may have fled to America after the conflict. On the basis of similarities she identified in historical and oral traditions, Stewart believed that these warriors were responsible for the introduction of the Athabascan languages to the continent, some...