Try an experiment: take a passenger along on a brief car trip--a jaunt to the supermarket, say. Have a nice conversation while you"re driving, and take a scenic route. Now, the next day, try to reconstruct the details of both the conversation and the trip. Chances are, unless something unusual happened along the way, that your memory of both will be indistinct, for we tend to forget the mundane--an example of what the cognitive scientist Daniel Dennett calls "rolling consciousness with swift memory loss." Steven Mithen, an archaeologist with an interest in psychology, believes that just such a consciousness obtained among early humans when they went foraging for food or made tools. The evolution of higher, more memory-laden consciousness, he continues, occurred only as a result of a cognitive trick that doubtless involved some trial and error. The trick, simply put, was to guess what the social behavior of some member of one"s social group might be in a given circumstance--to step outside one"s own mind, in other words, and enter another"s. This guesswork underlies the famed cave paintings of Altamira, an attempt to predict the behavior of migratory animals. It underlies as well another experiment: the development of agriculture, with the requisite predicting of how plants and animals might behave under a wide range of conditions. Mithen"s reconstruction of the ancestral human mind, laid out in a clear and accessible narrative, is a fine intellectual adventure. --Gregory McNamee