Haldane was born in Oxford, England, the son of well-known physiologist John Scott Haldane. As a boy, he participated in his father's experiments in human respiratory physiology, and as a student, he carried out breeding experiments on mice and guinea pigs. Haldane was educated at Eton and later attended New College, Oxford. Although he majored in mathematics, he excelled in classical studies and philosophy.

Haldane became an officer in the Black Watch regiment in France and the Middle East at the outset of World War I. After being wounded, he returned to study physiology at New College in 1919. He held a fellowship there until 1923, when he moved to Cambridge to work under English biochemist Frederick Gowland Hopkins for two years. After returning to London, Haldane accepted a position at University College as genetics chair and a part-time position at the John Innes Horticultural Institution at Merton. Haldane remained...