According to the Bible, Noah's Ark was a massive vessel built at God's command to save Noah, his family, and a core stock of the world's animals from the Great Flood. The story is contained in the Hebrew Bible's book of Genesis, chapters 6 to 9. According to one school of modern textual criticism — the documentary hypothesis — the Ark story told in Genesis is based on two originally quasi-independent sources, and did not reach its present form until the 5th century BC. Nevertheless, many Orthodox Jews and traditional Christians reject this analysis, holding that the Ark story is true, and that any perceived inadequacies can be rationally explained. The Ark story told in Genesis has extensive and striking parallels in the Sumerian myth of Utnapishtim, which tells how an ancient king was warned by his personal god to build a vessel in which to escape a flood sent by the higher council of gods. By the beginning of the 18th century, the growth of biogeography as a science meant that few natural historians felt able to justify a literal interpretation of the Ark story. Nevertheless, Biblical literalists continue to explore the region of the mountains of Ararat, in northeastern Turkey, where the Bible says Noah's Ark came to rest.