For more than half a century Sir Arthur Keith has been one of the world’s leading authorities on the physical evolution of man. As a young man, Sir Arthur spent some years of medical practice in Borneo and became interested in the comparative anatomy of the anthropoid apes and the relation of these higher primates to man. By dissections and other anatomical studies he accumulated the largest body of accurate scientific information on this subject available to students before Professor Adolph H. Schultz began his researches in this same field in the nineteen twenties. In 1901 Sir Arthur published his Human Embryology and Morphology, which is one of the few technical treatises on man’s embryology that is anthropological and primatological in its orientation. From 1908 onward Keith concerned himself with the problem of the transformation of the body and brain of the ape precursor into that of a human being. This subject led him into intensive studies of the skeletal remains of fossil men and apes, culminating in his great works, The Antiquity of Man (1925) and New Discoveries Relating to the Antiquity of Man (1931).

During the long years in which he was thus engaged, Sir Arthur was also considering the evolution and differentiation of the modern races of man, not only from the biological and anatomical viewpoints, but also on the bases of history, social anthropology, and psychology. Recently, as he approaches the end of his fruitful scientific career, this great anthropologist has produced two volumes dealing with human evolution in its entirety—a preliminary book Essays on Human Evolution (1946), and the present work.