Mammalian ear
There are two problems here: the early evolution of the ear, and its extraordinary sophistication.
As we saw in the first chapter, one of the chief distinctions between reptiles and mammals is that the former have a single earbone (the stapes) and at least four bones in the lower jaw, whereas mammals have two extra earbones, but only one j awbone. The evolutionary assumption is that some of the reptile's jawbones became embedded in the middle ear and finally transformed into the malleus (hammer) and incus (anvil) bones. The lack of evidence that this is, in fact, what happened (there are no transitional fossils) is frequently remarked upon by creationists (panel 14).
Panel 14
The chewing/hearing conundrum
The imagined step-by-step process leading up to the appearance of the mammal ear is, like the human eye, a favorite target in literature ridiculing the whole idea of evolution. This passage is by Douglas Dewar, a Fellow of the Zoological Society of London who became disenchanted with Darwinian theory and helped found the Evolution Protest Movement in Britain. During the ten years before his death in 1957, he was its president. Here he 'translates' into plain English an apparently plausible scientific account of the reptile/mammal jaw transformation written by Dr R. Broom, an authority on the fossils of South African mammal-like reptiles. The test was issued as part of a pamphlet by the EPM in 1965. Some reptile scrapped the original hinge of its lower jaw and replaced it with a new one attached to another part of the skull. Then five of the bones on each side of the lower jaw broke away from the biggest bone. The jaw bone to which the hinge was originally attached, after being set free, forced its way into the middle part of the ear, dragging with it three of the lower jaw bones, which, with the quadrate and the reptilian middle-ear bone, formed themselves into a completely new outfit. While all this was going on, the organ of Corti, peculiar to mammals and their essential organ of hearing, developed in the middle ear. Dr Broom does not suggest how this organ arose, nor describe its gradual development. Nor does he say how the incipient mammals contrived to eat while the jaw was being rehinged, or to hear while the middle and inner ears were being reconstructed.19
In its modern form, our ear (and that of animals) is intricate beyond imagination. Textbooks readily admit that its mechanism, particularly the way we can hear the pitch of a sound, is not at all well understood. The incomprehension stems from the complexity. The organ of Corti alone, a spiraling 3mm diameter ridge of cells in the inner ear that seems to play a crucial part in the way we hear pitch and direction of sound, contains some 20,000 rods and more than 30,000 nerve endings.
Yet within this complexity lies a further paradox (panel 15). Although nothing remotely as complicated can be found in the ear of reptiles, living or extinct, it is far from certain that we hear significantly better than they do. So where is the special advantage that, according to theory, would be naturally selected?
