Relating to or characteristic of atavism; showing primitive or ancestral traits that have reappeared in a modern individual.
From Latin 'atavus' (ancestor), combined with the English suffix '-ic', creating an adjective meaning 'of or relating to ancestral traits'.
An 'atavic' trait might be something like humans being born with vestigial tails or having an unusually strong gag reflex—physical remnants of our evolutionary past that occasionally pop back up in modern individuals.
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