In the article on "Clearing up myths about the Deming cycle and seeing how it keeps evolving", by Ron Moen and Clifford Norman, they refer to the first origins of PDCA in the work of Galileo on Designed Experiments and Francis Bacon's work on Inductive learning. The basic idea of Scientific method being - making a hypothesis, conducting experiment, learning about hypothesis through experiment results. Later the idea seems to have inspired I J Lewis and through him to Shewhart, giving a clear account of evolution period from 17th century.