[2] At Harvard, he serves in the departments of Organismic and Evolutionary Biology and Earth and Planetary Sciences.

He has discovered microfossil records of early life in Spitsbergen, East Greenland, Siberia, China, Namibia, western North America, and Australia,[1] and was among the first to apply principles of taphonomy and paleoecology to their interpretation.

[1][2] Among other things, Knoll and his colleagues were the first to hypothesize that rapid build-up of carbon dioxide played a key role in end-Permian mass extinction, 252 million years ago.

He received the Phi Beta Kappa Book Award for "Life on a Young Planet: The First Three Billion Years of Evolution on Earth".

In 2018, Knoll received the International Prize for Biology, conferred in Tokyo in the presence of the Emperor and Empress of Japan.