It is obvious that for one creature to resemble another can be of little or no benefit to either until the resemblance is tolerably close. It is, therefore, insufficient to prove the utility of the perfected resemblance. We may readily grant this and yet maintain that the origin of the resemblance cannot be due to the action of natural selection.
The Drongo-cuckoo (_Surniculus lugubris_) displays so great a likeness to the King Crow (_Dicrurus ater_) that it is frequently held up by Neo-Darwinians as an excellent example of mimicry among birds. But D. Dewar writes, on page 204 of _Birds of the Plains_: “I do not pretend to know the colour of the last common ancestor of all the cuckoos, but I do not believe that the colour was black. What then caused _Surniculus lugubris_ to become black and assume a king-crow-like tail?
“A black feather or two, even if coupled with some lengthening of the tail, would in no way assist the cuckoo in placing its egg in the drongo’s nest. Suppose an ass were to borrow the caudal appendage of the king of the forest, pin it on behind him, and then advance among his fellows with loud brays, would any donkey of average intelligence be misled by the feeble attempt at disguise? I think not. Much less would a king-crow be deceived by a few black feathers in the plumage of a cuckoo. I do not believe that natural selection has any direct connection with the nigritude of the drongo-cuckoo.”
Darwin was fully alive to this difficulty when he wrote: “As some writers have felt much difficulty in understanding how the first step in the process of mimicry could have been effected through natural selection, it may be well to remark that the process probably commenced long ago between forms not widely dissimilar in colour” (_Descent of Man_, 10th Ed., p. 324). Such a statement is of course quite inconsistent with the Neo-Darwinian position. “The conclusion which emerges most clearly,” writes Poulton (_Essays on Evolution_, p. 232), “is the entire independence of zoological affinity exhibited by these resemblances; and one of the rare cases in which Darwin’s insight into a biological problem did not lead him right was when he suggested that a former closer relationship may help us to a general understanding of the origin of mimicry. The preservation of an original likeness due to affinity undoubtedly explains certain cases of mimicry, but we cannot appeal to this principle in the most remarkable instances.”