The Asiatic theory of American origins, upheld by Joseph-Françis Laffiteau (1670-1740), Alexander von Humboldt (1769-1859), and Charles Lyell (1797-1875), was the most popular, although specific tall tales of Chinese discoveries were discredited; and it was reinforced by the fact of the narrowness of the Bering Strait and its frozen condition in winter. Long before the Norwegian author Thor Heyerdahl, ideas of Polynesian contacts were defended, and so were Welsh-even by Edward Burnett Tiler (1832-1917)-and Irish claims. In 1843 William H. Prescott, confronting the question in the context of Mexican civilization, surveyed the myths and theories deriving from discredited notions of the unity of the human race and in the end rejected Hebrew, Egyptian, Chinese, or Tartar origins for East Asia-but in a period "so remote, that this foreign influence has been too feeble to interfere with the growth of what may be regarded, in its essential features, as a peculiar and indigenous culture." In other words, prehistory was largely a matter of speculation, and scholars should confine themselves to recorded and accessible periods.(: