I believe it was Lamarck who posited a "theory of evolution" whereby he explained (as an example) the giraffe's long neck, by saying that the species saw tender leaves higher than the animals could reach, and that will made the succeeding generations have longer necks.
This is one of the other theories of evolution I mentioned in a post early on in this thread.
Incidentally, George Bernard Shaw was a believer in Lamarckian evolution, and used it as a premise for his play (fascinating reading, by the way) Back to Methuselah.