Speculations concerning the origin of the American Indian began almost as soon as it became known that America Septentrional was inhabited. Most current theories favor an Asiatic origin, with migration through northern Kamchatka and Alaska. This is supported by rather plentiful evidence. A few anthropologists postulate an island-hopping trans-Pacific migration at relatively low latitudes. This theory is supported by conclusive modern proof that such voyages are possible. Other proposed origins include Palestine (“The Lost Tribes of Israel”), Argentina (Ameghino's “Hombre Terciaro”), various lost continents (such as James Churchward's Mu), and other planets, some no longer extant. These latter theories are based either on misinterpreted evidence (such as the Hombre Terciaro), or overactive imagination (such as Mu), and merit no further consideration here.

Although the theory of Asiatic origin of the American Indian is the most widely accepted today, its first proposal seems quite difficult to locate, particularly as Columbus and his crewmen believed that the inhabitants of the New World were Asiatics.