ATAVISM
atavism, reversion, throwback
(noun) a reappearance of an earlier characteristic
Source: WordNet® 3.1
Etymology
Noun
atavism (countable and uncountable, plural atavisms)
The reappearance of an ancestral characteristic in an organism after several generations of absence.
The recurrence or reversion to a past behaviour, method, characteristic or style after a long period of absence.
(sociology) Reversion to past primitive behavior, especially violence.
Usage notes
Can be used both positively, to refer to past or ancestral characteristics, or pejoratively, referring specifically to past primitive characteristics.
A rather formal term; in popular speech the circumlocution skip a generation is often used for traits that occur after a generation of absence.
Source: Wiktionary
At"a*vism, n. Etym: [L. atavus an ancestor, fr. avus a grandfather.]
(a) The recurrence, or a tendency to a recurrence, of the original
type of a species in the progeny of its varieties; resemblance to
remote rather than to near ancestors; reversion to the original form.
(b) (Biol.) The recurrence of any peculiarity or disease of an
ancestor in a subsequent generation, after an intermission for a
generation or two.
Now and then there occur cases of what physiologists call atavism, or
reversion to an ancestral type of character. J. Fiske
Source: Webster’s Unabridged Dictionary 1913 Edition