He was educated at Winchester College. He became professor of biological diversity at the Department of Biology, University College London. He was co-director of the Centre for Ecology and Evolution, a centre of excellence in research and teaching formed by University College London, the Institute of Zoology (Zoological Society of London), Natural History Museum, Imperial College, Queen Mary, Royal Holloway and Kew Gardens. In 2013 he was distinguished lecturer on Organismic and Evolutionary Biology at Harvard University. His research has included work on the species concept central to evolutionary biology, along with hybridization and the process of speciation.
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- Academic Staff at UCL Department of Genetics, Evolution and Environment
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- Mallet J (September 2008). "Hybridization, ecological races and the nature of species: empirical evidence for the ease of speciation". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 363 (1506): 2971–86. doi:10.1098/rstb.2008.0081. PMC 2607318. PMID 18579473.
- "Linnean Society to award Darwin-Wallace medal on Darwin's 200th birthday". The Alfred Russel Wallace Website. Retrieved 26 June 2015.
- "The Darwin-Wallace Medal". The Linnean Society of London. Retrieved 28 February 2018.