The proper study of mankind is not merely Man, but Intelligence. 1 --Arthur C. Clarke, 1951 In the long-running television series "The X-Files," the original Deep Throat said to FBI Special Agent Mulder that "there are those like yourself who believe in the existence of extraterrestrial life." Ah, but that's not the question. If extraterrestrial life exists, most of it may be in simpler forms comparable to the one-celled organisms of Earth biology. Finding such life would be fascinating for scientists, but may be of only passing interest to the general public. What intrigues the average...