Reappearance of an ancestral trait after several generations is known as:

Correct Answer: Atavism

Atavism is the reappearance of an ancestral trait after several generations of absence. It occurs when dormant ancestral genes are re-expressed due to recombination or other genetic events.

Examples

• Extra toes in modern horses (ancestral three-toed horses had multiple digits)
• Dewclaws reappearing in certain dog breeds

Why Other Options Are Wrong

• Mutation: A sudden heritable change in genetic material — coined by Hugo de Vries (studied in Oenothera lamarckiana). Atavism is NOT a new change; it is revival of an old trait.
• Epistasis: One non-allelic gene masks another (intergenic interaction). Completely different mechanism from atavism.
• Linkage: Two genes of different traits located on the same chromosome — they tend to be inherited together (Mendel's 2nd law exception). Not related to trait reappearance.