Samuel George Morton (1799-1851), whose two major monographs were the Crania Americana (1839), An Inquiry into the Distinctive Characteristics of the Aboriginal Race of America and Crania Aegyptiaca (1844) concluded that the ancient Egyptians were not Negroid but Caucasoid and that Caucasians and Negroes were already distinct three thousand years ago. Since The Bible indicated that Noah's Ark had washed up on Mount Ararat only a thousand years before this Noah's sons could not account for every race on earth. According to Morton's theory of polygenism the races had been separate from the start. Josiah C. Nott and George Gliddon carried Morton's ideas further. Charles Darwin, who thought the single-origin hypothesis essential to evolutionary theory, opposed Nott and Gliddon in his 1871 The Descent of Man, arguing for monogenism.