Sir Alan Sterling Parkes FRS CBE (10 September 1900 - 17 July 1990) was an English reproductive biologist credited with Christopher Polge and Audrey Smith for the discovery that spermatozoa can be protected against induced damage induced by freezing and low-temperature storage using glycerol. This work enabled the development of the field of cryobiology. Hall was educated at Willaston School. He published on the reproductive effects of X-rays on mice, hormonal control of secondary sexual characteristics in birds, and aided Hilda Bruce in research that established the Bruce effect.