Frans de Waal has spent four decades at the forefront of animal research. Following up on the best-selling Are We Smart Enough to Know How Smart Animals Are?, which investigated animal intelligence, Mama's Last Hug delivers a fascinating exploration of the rich emotional lives of animals. Mama's Last Hug begins with the death of Mama, a chimpanzee matriarch who formed a deep bond with biologist Jan van Hooff. When Mama was dying, van Hooff...