Darwinism is not a testable scientific theory, but a metaphysical research program.

Popper later retracted his criticisms | 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. | "Natural selection and the emergence of mind" dialectica Vol. 32 (1978), p. 339-355; republished in Evolutionary Epistemology, Rationality, and the Sociology of Knowledge (1987) edited by Gerard Radnitzky and W. W. Bartley, III