Although it is difficult to ascertain precisely the time at which the study of individual differences became recognized as a specialty within the psychological sciences, there appears to be much agreement among historians that its development was fostered primarily within the United States during the late 19th century. This paper examines the beginnings of research and application concerning individual differences and their social context in which it proliferated. Within this context, the nature versus nurture controversy is introduced, and a discussion about its importance to the field of developmental psychology follows. Charles Darwin's research was not always fully understood by others and some of the resulting pseudoscientific philosophies are discussed. The Eugenics movement, Social Darwinism, and intelligence testing are examined, with emphasis on the latter. Late nineteenth and early twentieth century conceptions of human development are explored. Sex differences in intelligence, functionalism, and behaviorism are also discussed in historical context. Contains 10 references. (JBJ)