In this provocative work, the historian Elof Carlson explores how new fields of the life sciences emerge. Some scientists describe new theories, experiments, discoveries, or the use of new technology as paradigm shifts. Others call them scientific revolutions. The idea of paradigm shifts was introduced in 1962 by Thomas Kuhn, using as an example the emergence of the Copernican view that the sun, not the earth, was the center of the known universe. Carlson, however, argues by contrast the history of the life sciences is not an unbroken sequence of paradigm shifts but instead rather messy, with lots of contending ideas. What scientists believe to be true is not arrived at by consensus but by the weight of experiments and their results. Most of the time new tools lead to new theories, a process Carlson calls "incrementalism", an evolving human enterprise that depends on new technologies for generating new data and scientific progress.