atavism (ătˈəvizəm) [key], the appearance in an individual of a characteristic not apparent in the preceding generation. At one time it was believed that such a phenomenon was thought to be a reversion of "throwback" to a hypothetical ancestral prototype. The term is seldom used today since science has shown that such abnormal characteristics can be explained by the inheritance of a pair of recessive genes. See Mendel.
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