After fifteen years of civil rights struggle to assure black Americans of the full rights of citizenship and four decades of work by scientists to dismantle the notion of a biological basis for racial difference, Nobel Prize-winning physicist William Shockley became a controversial figure in the 1970s when he argued that black Americans were genetically endowed with inferior intelligence. He was rebuffed by the National Academy of Sciences in 1970, when it refused to conduct a study along these lines. Shockley was increasingly unpopular on U.S. campuses by late 1973, when he was prevented from fulfilling speaking engagements by students who protested that he was a racist and a Fascist. In 1974 anthropologist Peggy Sanday offered a study many believed discredited Shockley's views, arguing that IQ_differences were "exclusively a matter of environment."