1. relating to or characteristic of an ancestor or ancestors; inherited from a remote past
Usage: often used in biology and anthropology to describe traits that reappear after many generations
2. reverting to or suggestive of a more primitive or savage state; showing a return to earlier, less civilized behavior or instincts
Usage: often used figuratively to describe human behavior or impulses

Examples

• The scientist discovered atavistic features in the fossil that linked it to ancient species.
• His atavistic fear of the dark seemed to override his rational mind.
• The atavistic instinct to protect one's territory is still present in modern humans.
• Some viewed the violent behavior as an atavistic throwback to humanity's savage past.
• The atavistic traits in the organism suggested it had not evolved as much as its relatives.
• She felt an atavistic urge to flee when confronted with danger.