Thoughts from a Psychologist By Julia A . Sherman

Clinical psychologists don’t often venture into the world of paleoanthropology, but the hypothesis that bipolar disorder evolved as an adaptation to Pleistocene climatic conditions, landed me in this fascinating and contentious arena. Bipolar disorder is correlated with a cold adapted build, and its symptoms are consistent with seasonal adaptation. For example, symptoms of major depression, such as slowing and loss of interest in usual activities, are congruent with the idea of energy conservation during long, cold winters, which was particularly important for women (their reproductive functioning requires sufficient body fat). The increased social and goal-directed behaviors of hypomania and mania facilitated accomplishment of tasks necessary for survival during the short period of fair weather. If bipolar disorder evolved as an adaptation, how, where, and when did this occur? Although the most likely ancestral candidate for bipolar disorder might seem to be Neanderthal, the most cold adapted species known, genetic analysis makes that unlikely. The intriguing possibility remains that bipolar disorder was common among them. Excluding Neanderthal leaves two ancestral sources for bipolar disorder. Either it evolved among an ancient people who intermixed with the most recent migration of Homo sapiens from Africa, or it evolved among a subset of the latter living in glaciated areas of the Old World. When the genes responsible for vulnerability to bipolar disorder are identified, they may help us sort out our evolutionary history. Seeking further enlightenment, I eagerly turned to these new books. The title, Neanderthal’s Necklace, subtly expresses Arsuaga’s view that Neanderthal is a parallel human group that, “lived much as the Cro Magnons – our ancestors did – worshiping, socializing, and hunting,” to quote the dust jacket. The book is refreshing and charming