Clair Patterson By IanandLauren 1922 Born in Mitchellville, Iowa 1943 Graduation from Grinnell College 1944 Worked on Manhattan Project 1948 Begins work on uranium and lead dating in zircon crystals 1951 Receives Ph.D from University of Chicago 1953 Begins career at CalTech 1956 Determines the age of the earth 1964 Trips to ice caves in Antarctica and Greenland 1965 Tries to bring public's attention to danger of lead poisoning 1971 Excluded from National Research Council panel on atmospheric lead contamination 1986 Leaded gas begins to be phased out 1995 Death in California 1998 Lead levels in humans decreased by 80%