Medawar, MEHD uh wuhr, Sir Peter Brian (1915-1987), an English zoologist, shared the 1960 Nobel Prize for physiology or medicine with Sir Macfarlane Burnet. In 1953, Medawar and his colleagues proved Burnet's idea on acquired immunological tolerance. This idea suggested that under certain conditions, tissues and organs can be transplanted from one animal to another and function properly even though the animals are not related. Medawar's research played an important role in the development of human transplant surgery.