Mixter graduated from Wheaton College, Illinois, in 1928 with a major in literature and a minor in biology.
in zoology from Michigan State College and a Ph.D. in anatomy from the University of Illinois School of Medicine in Chicago, shortly after returning to Wheaton to teach.
[4] After a brief flirtation with flood geology, Mixter advocated the viewpoint that he called progressive creationism for the rest of his life.
Along with Wheaton compatriot J. Frank Cassel, he led the ASA away from antievolutionism,[1] bringing evangelicals into harmony with modern biology,[5] whilst stopping short of an outright endorsement of theistic evolution.
He married Emilie Claus (died August 2, 1998) on June 27, 1931, and they had four children: Wilbur, Joan (Mrs. Jerry Sweers), Ruth, Priscilla (Mrs. Gordon Gault).