W. E. B. Du Bois (1868–1963), one of the first African-American sociologists, was the first sociologist to use sociological concepts and empirical research methods to analyze race as a social construct instead of a biological reality. Beginning in 1899 with his book "The Philadelphia Negro", Du Bois studied and wrote about race and racism throughout his career. In his work, he contended that social class, colonialism, and capitalism shaped ideas about race and racial categories. Social scientists largely abandoned scientific racism and biological reasons for racial categorization schemes by the 1930s. Other early sociologists, especially those associated with the Chicago School, joined Du Bois in theorizing race as a socially constructed fact. By 1978, William Julius Wilson (1935–) argued that race and racial classification systems were declining in significance, and that instead, social class more accurately described what sociologists had earlier understood as race. By 1986, sociologists Michael Omi and Howard Winant successfully introduced the concept of racial formation to describe the process by which racial categories are created. Omi and Winant assert that "there is no biological basis for distinguishing among human groups along the lines of race."