ATAVISM (Latin atavtis ; originally "an cestor," later specialized as ((great-great-great grandfather'') ; in biology, the reappearance in an organic being of specific ancestral peculiari ties which have not appeared in intermediate generations, or of peculiarities of ancestral side branches not represented in the direct line. It is often loosely used as synonymous with rever sion, but in scientific usage the latter is not the reappearance of single characteristics, and certainly not of abnormal ones, but the return in general type to the primitive type from which the special race was evolved. In this sense, it may be said that reversion is the extreme backward limit of atavism. For example, the birth of a six-fingered child with a six-fingered grandfather or uncle but normal parents would be atavism; but the approach of human beings left on a desert island to the prognathous and hairy type of the simians, were it conceivable, would be reversion. Sometimes the two are hardly to be discriminated; thus, the appearance of a tail-bone or pointed ears would be an atavism recalling the primitive type, as are horses with toes, yet not quite a reversion. A
true reversion is the banded pigeon which is a frequent •sport(' among fancy breeds; and the still commoner mongrel ((yellow dog," a rever sion to the jackal type. Atavisms are part of the perpetual family wonders, the reproduction of minute special features, habits, tricks of be havior, even tastes and fashions of speech, char acteristic of distant relatives or far-back ances tors, but perhaps obliterated for long periods. In sociology, especially criminology, the word is used precisely in the sense of reversion to primi tive instincts and passions, supposed to be over laid or suppressed by civilization. The criminal on this, theory is a being who has lost his evolved characteristics, and gone backward to the primitive savage. This, however, has too many flaws to be scientifically acceptable.