Mother NatureBy: Sarah Hrdy [A] magisterial survey of childbearing through the ages . . . It wams the heart to witness the fierce loyalty this sophisticated feminist professor of anthropology . . . bears towards her paleolithic sisters.San Francisco Chronicle Maternal instinctthe all consuming, utterly selfless love that mothers lavish on their childrenhas long been assumed to be an innate, indeed defining element of a womans nature. But is it? In this