Sapp was born in Halifax, Nova Scotia. He completed his BSc hons (Biology) at Dalhousie University in 1976 before earning his MSc and Phd at the Institut d’histoire et de sociopolitique des sciences, at l'Université de Montréal in 1984. He subsequently held an appointment at the University of Melbourne for eight years, where he also served as chair of the Department of History and Philosophy of Science. He was Andrew Mellon Fellow at the Rockefeller University, 1991-92. He held the Canada Research Chair (tier 1) in the History of the Biological Sciences at l’Université du Québec à Montréal from 2001-2003 before returning to York University where he has been a professor since 1992.
Sapp's book Evolution by Association (1994) is the first book to document the history of symbiosis in depth. It was described in a review as a "fine piece of scholarship". He subsequently introduced the terms "symbiome" and "symbiomics" to biology in his book Genesis: The Evolutionary of Biology (2003). He developed this line of historical research beyond classical neoDarwinian biology further in his book on the history of microbial phylogenetics, The New Foundations of Evolution: On the Tree of Life (2009). He is also known for his writing on the coral reef crisis, focusing in detail on the outbreaks of crown of thorns starfish and coral bleaching. His recent book Coexistence: The Ecology and Evolution of Tropical Biology" (2016) focuses on the history of tropical biology, and on what he calls the "central enigma" in tropical ecology.