Hoaxes like Piltdown Man and Calaveras Man, and honest mistakes like Nebraska Man and Hesperopithecus, are, in time, exposed. Science picks itself up, shakes itself off, and moves on. All causes have effects. That is, the cause of intelligence must be intelligent. Also, regress all causes in time and you must conclude that there was a first cause - God.
Animal manure makes fruit trees grow better.
Purpose is, in part, what we are accustomed to perceiving. Finally, not everything is so purposeful and beautifully designed. In addition to the problems of evil, disease, and deformities that creationists conveniently overlook, nature is filled with the bizarre and seemingly unpurposeful. Male nipples and the Panda's thumb are just two examples that Gould is fond of flaunting as purposeless and poorly designed structures. Something cannot be created out of nothing, say scientists.