Until the dawn of the twentieth century, exploration of Earth's surface was limited to the surface itself. The summits of the highest mountains, the depths of the oceans, and sky and space were unexplored. Technological advances, as well as fundamental shifts in scientific theory, opened the entire world, and beyond, to exploration. The twentieth century was the golden age of discovery, rivaled only by the Copernican Revolution and the European discovery of the New World in the fifteenth century.

In 1859, Charles Darwin published a natural history work that sparked great controversy. Darwin's book, On the Origin of Species, was a compilation of his scientific observations from an expedition to the Galapagos Islands. Darwin's observations led him to construct a model of the evolution of various animal species, including man. Over the course of his career, Darwin built upon...