Thomas Cavalier-Smith

Thomas (Tom) Cavalier-Smith, FRS, FRSC, NERC Professorial Fellow (21 October 1942 – 19 March 2021), was a professor of evolutionary biology in the Department of Zoology, at the University of Oxford.

His research has led to discovery of a number of unicellular organisms (protists) and advocated for a variety of major taxonomic groups, such as the Chromista, Chromalveolata, Opisthokonta, Rhizaria, and Excavata. He was known for his systems of classification of all organisms.

Cavalier-Smith was born on 21 October 1942 in London. His parents were Mary Maude (née Bratt) and Alan Hailes Spencer Cavalier Smith.

He was educated at Norwich School, Gonville and Caius College, Cambridge (MA) in Biology and King's College London (PhD) in Zoology. He was under the supervision of Sir John Randall for his PhD thesis between 1964 and 1967; his thesis was entitled "Organelle Development in Chlamydomonas reinhardii".

From 1967 to 1969, Cavalier-Smith was a guest investigator at Rockefeller University. He became Lecturer of biophysics at King's College London in 1969. He was promoted to Reader in 1982. From the early 1980s, Smith promoted views about the taxonomic relationships among living organisms. He was prolific, drawing on a near-unparalleled wealth of information to suggest novel relationships. In 1989 he was appointed Professor of Botany at the University of British Columbia. In 1999, he joined the University of Oxford, becoming Professor of evolutionary biology in 2000.

Thomas Cavalier-Smith died in March 2021 following the development of cancer.

Cavalier-Smith was a prolific taxonomist, drawing on a near-unparalleled wealth of information to suggest novel relationships. His suggestions were translated into taxonomic concepts and classifications with which he associated new names, or in some cases, reused old names. Cavalier-Smith did not follow or espouse an explicit taxonomic philosophy but his approach was closest to evolutionary taxonomy. He and several other colleagues were opposed to cladistic approaches to taxonomy arguing that the goals of cladification and classification were different; his approach was similar to that of many others' broad-based treatments of protists.

The scope of Cavalier-Smith's taxonomic propositions was grand, but the numbers and composition of the components (taxa), and, often, their relations were not stable. Propositions were often ambiguous and short-lived; he frequently amended taxa without any change in the name. His approach was not universally accepted: Others attempted to underpin taxonomy of protists with a nested series of atomised, falsifiable propositions, following the philosophy of transformed cladistics. However, this approach is no longer considered defensible.