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Category Archives: Our Town
CAN YOU EAR ME NOW?
About that hissing sound in your ear? In the early 19th century a startling discovery was made that proved Darwin’s theory of evolution before he ever dreamed of joining the voyage of the Beagle. This discovery was made by a German biologist, Karl Reichert, who to his great astonishment found that two of the ear bones in mammals are the same thing as parts of the jaw bones in reptiles. In short, two of the ear bones in mammals -including homo sapiens– came from the gill arch that formed the jaw of a reptile.
In his brilliant bestseller, Your Inner Fish: A Journey into the 3.5 Billion Year History of the Human Body, paleontologist, Neil Shibun, by examining fossils and DNA shows how our hands evolved from fish fins, our heads are organized like long-extinct jawless fish, and how major segments of our human genome look and function like those or worms and bacteria.
But perhaps none are as fascinating as the evolutionary history of our human middle ear, which like all mammals has three bones. Reptiles and amphibians have only one bone; fish none.
Building on Rechert’s amazing discovery around 1912 another German anatomist, Ernst Gaupp found that the single bone in the reptilian middle ear is the same as the stapes of mammals and that the the two other bones of the middle ear -the malleus and incus- evolved from bones set in the back of the reptilian jaw.
Neil Shibun asks: Why do mammals need a three-boned middle ear? His answer: “This little linkage forms a lever system that allows mammals to hear higher-frequency sounds than animals with a single middle-ear bone. Bones originally used by reptiles to chew evolved in mammals to assist in hearing.”
Who says science isn’t awesome!
Posted in Clarion Causes, Our Town, Winter Edition 2013 Leave a comment