William Calvin, a neurophysiologist and author of The River That Flows Uphill: A Journey from the Big Bang to the Big Brain, attempts to reclaim the study of human consciousness from physicists like Roger Penrose. Physicists, Calvin suggests, reduce the mind to subatomic particles and mathematical equations, whereas those in his specialty see the seat of consciousness and intelligence in higher levels of brain physiology--the neurons, synapses, and cortex. Calvin is a Darwinist who regards the unique level of human consciousness as the product of evolutionary forces that began with the ice ages two million years ago. The human response to this natural threat, he argues, was to develop mental faculties that allowed high-level communication and, thus, cooperation, leading to complex language capabilities and the distinguishing human characteristic of abstract thought.