James Alexander Thwaits (sometimes Thwaites), surgeon and gynaecologist, was the son of the land surveyor James Alexander Thwaits and his wife Catherine Dorothea, born Bantjes. He attended the South African College, Cape Town, in 1888 only and that year passed the matriculation examination of the University of the Cape of Good Hope. Continuing his studies at the University of Edinburgh he qualified as Bachelor of Medicine (MB) and Master in Surgery in 1895. After his return to South Africa he was registered to practice in the Transvaal in 1899 and after the Anglo-Boer War (1899-1902) did so in Johannesburg. After a few years he returned to the University of Edinburgh and in 1909 qualified as Doctor of Medicine (MD) and was admitted as a Fellow of the Royal College of Surgeons of Edinburgh.
Thwaits contributed an article on 'Radiotherapeutics'to the Transvaal Medical Journal (February 1910, Vol. 5(7), pp. 146-150) in which he discussed the uses and abuses of X-rays in medicine and the effects of over-exposure to X-rays and radium. He became a member of the South African Association for the Advancement of Science in 1903, but his membership lapsed before 1910. In December 1908 he married Violet Brice, but they had no children.