atavistic

This return to something more primitive is an unhealthy atavistic tendency and makes for both racial and individual inferiority.

Deering was very human and fought against an atavistic shrinking from the dark and loneliness.

My spine, too, like Conlon's, registered an authentic shiver of protest and atavistic fear.

War is old--atavistic, a confession of failure, evidence of retrogression.

The probability, in this case, is that the atavistic variety will find its way into a pie, instead of being kept as a pet.