Atavism (noun)

The reversion to a supposed earlier type of organism in the evolutionary development of an organism or group, as in the reappearance of a lost structural character in a species after an interval of absence.

Origin:

Late 19th century: from french atavisme, from atavus, from latin atavus "great-great-grandfather", from avus "grandfather".

Examples:

1. Atavism is the reappearance in an individual of characteristics of an ancestral species.
2. The atavism of the tail in the human embryo is a well-known example of this phenomenon.
3. The atavism of certain traits in domesticated animals is often used to trace the evolutionary history of a particular breed.
4. Some scientists have suggested that the atavism of certain genetic traits in certain individuals may be responsible for certain diseases.
5. The atavism of the human appendix, a vestigial organ with no known function, is an example of a trait that has lost its original function in the course of evolution.