The reappearance of primitive or ancestral characteristics in a modern individual or organism that were thought to be lost through evolution.
From Latin 'atavus' (ancestor) combined with the suffix '-ism', coined in the 19th century by evolutionary biologists to describe evolutionary reversions.
Atavism fascinated Victorian scientists because it seemed to prove that evolution was real—if a whale grows hind leg bones or a human is born with a tail, it shows we're carrying our evolutionary history literally inside our bodies.
Complete word intelligence in one call. Free tier — 50 lookups/day.