Middle ear muddle reported in news@nature 10 February 2005 and New Scientist, 19 Feb 2005, p16. All mammals have a single bone in their lower jaw and three bones in their middle ears. Reptiles have many bones in their jaw and one bone in their middle ear. Evolutionary theory says that the three-boned mammalian ear evolved when three bones from each side of the reptile jaw detached themselves and moved into the ear, leaving one bone for the jaw. Because all mammals have a three boned middle ear, and it is so complex, evolutionary scientists believe it must have only evolved once, in a primitive mammal that evolved into the three types of mammals that now exist, i.e. monotremes, marsupials and placentals.

A team of scientists led by Thomas Rich of Museum Victoria and Monash University, are now claiming that the complex three-boned mammal ear evolved twice. They examined jawbones of an extinct animal named Teinolophus trusleri, which is considered to be the oldest monotreme mammal, and found that it has “a large groove in its adult jawbone, which indicates that the smaller bones had not yet detached.: Teinolophus is believed to have lived after monotremes split from the marsupials and placentals, so modern monotremes must have evolved the three boned structure separately. The description of the jaw was originally published in Science, vol. 307, p910, 11 Feb 2005. On p811 of that issue Rich’s paper is introduced with the following claim: “Rich et al now show that the ear of the earliest known monotreme, from the Early Cretaceous, has only one bone.”

Editorial Comment:Rich’s paper points out Teinolophus is known from six mandibular fragments”, which means they have not found its ear. Therefore they cannot possibly have proven it only “has one bone”. Neither have they found the three small bones that are supposedly still attached to the jaw but are in the process of evolving into ear bones. What they have found is a jawbone with a large groove in it. As the animal that owned it is extinct, and no other parts of its body have been preserved, scientists can only speculate what the groove was for. They may believe it contains small bones on their way to becoming ear bones, but that belief is based on a prior faith in evolutionary theory, not on scientific observation. (Ref. transition, mammals, hearing)


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