Mark Twain's life (1835-1910) parallels the rapid development of geology and paleontology in the late 19th and early 20th centuries. Twain's use of geology and paleontology in his writing evolved along with the science. In the 1860s through the 1880s he sometimes used geological images to embellish a story, but in some of his lesser known works he was aggressively skeptical of the ability of scientists to reconstruct the details of earth history, and he ridiculed the gullibility of journalists and the public in believing the scientists. Twain's skeptical phase coincides with the development of the geologic time scale and the appearance of Darwin's books The Origin of Species (1859) and The Descent of Man (1871). Twain's skeptical essays may thus be viewed as a reflection of society's struggle to deal with the disturbing new paradigms of deep geologic time and Darwinian evolution. As early as 1870, Twain's private correspondence contains a reference to the insignificance of man in the context of geologic time and cosmic distances. In the 1880s his published writings became increasingly cynical and antagonistic toward Christianity. After 1884 Twain no longer expressed a skeptical attitude toward geology and paleontology in his writings. Rather, he used the emerging insights from these fields to communicate his disillusionment with biblical views. In his 1903 essay "Was the world made for man?" Twain discussed, without the sarcasm of earlier years, the views of Charles Lyell and Lord Kelvin about the age of the earth. In this case he used these views to satirize the biblical perspective that the events of earth history occurred specifically to prepare earth for humans. The evolution of Twain's use of geology and paleontology reflects, and helped to bring about, an increasing credibility and respectibility for these fields within American society, at the expense of biblical literalism.