This textbook deals with the nature origins development and causes of human variety and with the biological organization of past and present human populations. It is divided into 4 sections. These cover some general principles of evolutionary theory the principle of the Primates the fossil evidence for human evolution aspects of Primate behavior the principles of human genetics as applied to population studies systematic descriptions of human variation the nature of human growth and the factors which determine it varieties of human physique and other constitutional traits and the ecology of human populations considered especially in terms of adaptation processes. The book is intended primarily for students of human biology biological anthropology human sciences and medicine but it should continue to be of value also to everyone interested in the population biology of man.