ONE MAJOR and inevitable work remained. Back in the 1830's, when Darwin had become convinced that species are mutable, he "could not avoid" the thought that man must come under the same law. For his own satisfaction, he told himself, he collected notes on the origin and descent of man--in some of the big portfolios into which he always slipped reserve materials.
He did not use this evidence in The Origin because he thought it unfair to parade his views without giving all the material to support them. And time did not permit that. But Darwin also was fearful of the prejudices he knew would be aroused by any out-and-out statement that man had descended from lower animals.
When he was in the midst of writing The Origin of Species, Wallace asked him in a letter if he would discuss man. Darwin's answer was: "I think I shall avoid the whole subject, as so surrounded with prejudices; though I fully admit that it is the highest and most interesting problem for the naturalist." Nevertheless, his scrupulous regard for the whole truth made him feel that he could not conceal his views.
Many years later, in his autobiography, Darwin explained the famous sentence with which he resolved his conflict: "Although in The Origin of Species the derivation of any particular species is never discussed, yet I thought it best, in order that no honorable man should accuse me of concealing my views, to add that by the work 'light would be thrown on the origin of man and his history.'"