noun
atavism; reversion to ancestral traits
Technical term in genetics for the reappearance of ancestral characteristics after several generations of absence.
その突然変異は先祖返りの一例と考えられている。
That mutation is considered an example of atavism.
生物の進化において、先祖返りは稀に観察される現象だ。
In biological evolution, atavism is a rarely observed phenomenon.