This paper is the first chapter of a book and is divided into six sections. The first section discusses race taxonomy, the Negro American's origins from Africa, and the origin of race differences. The second section investigates the genetic aspects of race differences in intellectual performance, and includes a lengthy introductory discussion on the dialectics of heredity and environment. The third section deals with the genetic aspects of social class differences, while section four covers both race and class differences. The fifth section deals with the relationship between intelligence and family size in an introductory fashion, and the final section consists of a one-paragraph summary of the material covered in the chapter. A list of references and a glossary of terms are appended. (JF)