Oscar Riddle, born in Indiana in 1877, was an ardent evolutionist and a key player in the founding of the National Association of Biology Teachers in 1938. He studied heredity and behavior in domestic pigeons and doves with Charles O. Whitman of the University of Chicago, received his Ph.D. in zoology in 1907, and in 1912 began a long career at the Carnegie Institution. He is best known for his 1932 discovery of prolactin, the “mother love” hormone. Whitman founded and directed the Marine Biological Laboratory at Woods Hole and cared for Martha, the world's last passenger pigeon, who died in the Cincinnati Zoo in 1914.