Will we ever find a primer for decoding messages from extraterrestrials? Last month, anthropologists who gathered for a major conference in Atlanta, Georgia heard some news that will be sobering for SETI enthusiasts: it may be much more difficult to understand extraterrestrials than many scientists have thought before. Among the sessions held during December’s annual meeting of the American Anthropological Association was one called "Anthropology, Archaeology, and Interstellar Communication: Science and the Knowledge of Distant Worlds." The session included papers by scholars from such diverse fields as astronomy, archaeology, anthropology, and psychology. Is there a Cosmic Rosetta Stone, they asked,...