Most amazing of all is the evolutionary transition to the mammalian middle ear. In reptiles, as in amphibians and fishes, there is a single hearing bone, the stapes, which is simply a straight rod that links the eardrum to the hearing structures of the inner ear and the brain. You hear yourself chewing because parts of your hearing structure evolved from reptilian jawbones. But the malleus and incus have moved into the middle ear from their former function as the reptilian jaw joint. At a certain point, in the Late Triassic, the reptilian jaw joint had shifted function.
Evolutionary transitions are highly predictable.
The new fossil finds that hit the headlines are all concrete evidence of evolutionary transitions. Dinosaurs with feathers and whales with legs are pretty startling discoveries, but biologists were convinced they existed from the predictions of their evolutionary trees. Darwin's observations of species relationships provided major clues to speciation. The single great tree of life is profound evidence for evolutionary transitions. Darwin, as he toured South America and the Galapagos Islands in the 1830s, became increasingly puzzled about the distributions of plants and animals, both geographically and geologically.