Given the task definition and input, reply with output. This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

According to John N. Gray, Popper held that "a theory is scientific only in so far as it is falsifiable, and should be given up as soon as it is falsified." By applying Popper's account of scientific method, Gray's Straw Dogs states that this would have "killed the theories of Darwin and Einstein at birth." When they were first advanced, Gray claims, each of them was "at odds with some available evidence; only later did evidence become available that gave them crucial support." Against this, Gray seeks to establish the irrationalist thesis that "the progress of science comes from acting against reason."

Which two prominent scientists advanced theories that John N. Gray claims would never have survived the scientific method Popper describes?