Robert McNeill Alexander was a British Zoologist and an authority in the field of biomechanics. Until 1970 he was mainly concerned with fish, investigating the mechanics of swim bladder, tails and the fish jaw mechanisms. Subsequently he concentrated on the mechanics of terrestrial locomotion, notably walking and running in mammals, particularly on gait selection and its relationship to anatomy and to the structural design of skeletons and muscles.
Alexander was born in Lisburn, Northern Ireland and educated at Tonbridge School, Trinity Hall, Cambridge and the University of Wales.
After holding a lectureship at University College of North Wales 1958-1969, he was Professor of Zoology at the University of Leeds from 1969 until his retirement in 1999, when the title of emeritus professor was conferred on him.
He was Secretary of the Zoological Society of London 1992-1999. He was President of the Society for Experimental Biology 1995-1997, President of the International Society of Vertebrate Morphologists 1997-2001 and editor of the Proceedings of the Royal Society B 1998-2004.
Alexander married Ann Elizabeth Coulton in 1961. He died in 2016 at the age of 81.