"I took several short excursions as a relaxation, and one longer on to the Parallel Roads of Glen Roy, an account of which was published in the 'Philosophical Transactions.' This paper was a great failure, and I am ashamed of it. Having been deeply impressed with what I has seen of the elevation of the land of South America, I attributed the parallel lines to the action of the sea; but I has to give up this view when Agassiz propounded his glacier-lake theory. Because no other explanation was possible under our then state of knowledge, I argued in favour of sea-action; and my error has been a good lesson to me never to trust in science to the principle of exclusion. " Charles Darwin, Autobiography
This is a great lesson on why we don't use "prove" in science. Proofs are for mathematics only. So Darwin developed a hypothesis that fit the data it just happened that another hypothesis explained his observation better. Why? Agassiz developed a theory that explained the lines in rock and much more. That is, Darwin's hypothesis explained the lines and only the lines but Agassiz explained many more phenomena (including u-shaped valleys, and those huge boulders that don't belong in the landscape but are too large to move). We should always have multiple working hypotheses and never consider any one the hypothesis unless tested against many others.