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A small cob of maize remains among shards of pottery at an ancient Native American dwelling site in Utah. At the time maize was initially domesticated by Native Americans in Mexico, about 10,000 years ago, ears of maize, containing the kernels, were only about an inch long. Today, thanks to millennia of selective breeding, the ears are roughly seven times that size.

in animals or plants. A scientist cannot arrange marriages to study why children with albinism are born in one family, deaf and non-verbal children in another family, and children with blond hair and blue eyes in another. The geneticist must get his information from the results of marriages that have happened. But mathematical techniques have been invented for analyzing this sort of information. Mendel’s biographer Hugo Iltis said that Mendel searched through the parish registers of Brno to find inherited characteristics in residents. There is no evidence that he found what he was looking for. But the mathematical rules of chance that Mendel proved to work in the inheritance of color, shape, and size of pea plants have been found to apply equally to humans.

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