1. the reappearance of a characteristic or behavior in an organism that had disappeared in earlier generations; a throwback.
Usage: commonly used in biology and evolutionary contexts
2. a primitive or ancestral trait, instinct, or mode of behavior that resurfaces in a modern person or society.
Usage: used figuratively in psychology, sociology, and cultural criticism

Examples

• The presence of a tail in a human fetus is considered an atavism from our evolutionary past.
• Some scientists view certain aggressive behaviors as atavisms from our primate ancestors.
• The critic dismissed the movement as an atavism that rejected modern artistic values.
• Vestigial organs are often cited as examples of atavism in human anatomy.
• The political ideology was criticized as an atavism of outdated nationalist thinking.
• Biologists study atavisms to better understand evolutionary development and genetic inheritance.