Sir Karl R. Popper is the philosopher of science who championed the idea of falsification.
Many Creationist books have printed this quote:
"I have come to the conclusion that Darwinism is not a testable scientific theory, but a metaphysical research programme - a possible framework for testable theories."If you read the book, Popper is actually raising the famous "natural selection is a tautology" objection. Popper recanted two years later:
Unended Quest: An Intellectual Autobiography 1976, La Salle, IN: Open Court Press
"I have changed my mind about the testability and logical status of the theory of natural selection; and I am glad to have an opportunity to make a recantation. ...and he repeated the recantation three years after that:
The theory of natural selection may be so formulated that it is far from tautological."
Natural Selection and the Emergence of Mind, Dialectica 32:339-355, 1978. See 344-346 for this quote.
"... some people think that I have denied scientific character to the historical sciences, such as paleontology, or the history of the evolution of life on Earth; or to say, the history of literature, or of technology, or of science.
This is a mistake, and I here wish to affirm that these and other historical sciences have in my opinion scientific character; their hypotheses can in many cases be tested."
Letter to New Scientist 87:611, 21 August 1980