By the best selling author of "The Descent of Woman", the first popular account of what is known as the "aquatic ape" thesis. Modern homo sapians is in many respects a peculiarly evolved animal, and traditional accounts of our evolution are less-than convincing in explaining why we are almost hairless, why we walk on two feet, why we sweat from entirely different glands from all other apes, why human females are always sexually responsive and so on. In this book the case for the theory that we spent part of our evolutionary development as a semi-aquatic mammal, a theory that can explain all these peculiarities, is discussed.