|1.||the recurrence in a plant or animal of certain primitive characteristics that were present in an ancestor but have not occurred in intermediate generations|
|2.||reversion to a former or more primitive type|
|[C19: from French atavisme, from Latin atavus strictly: great-grandfather's grandfather, probably from atta daddy + avus grandfather]|
atavism at·a·vism (āt'ə-vĭz'əm)
The appearance of characteristics that are presumed to have been present in some remote ancestor; reversion to an earlier biological type.