Atavism is

Explanation

Atavism is the sudden reappearance or refunctioning of some ancestral organs, which haved either completely disappeared or are present as vestigial organs. Iit supports the idea of organic evolution, that living organisms have the ability to develop even lost or non-functional structures. For example, long and dense body hair, ability to move pinna is some individuals, birth of a human boby with a small tail etc.