primitive instinct

Translations
примитивный инстинкт
Fear is often considered a primitive instinct.
Страх часто считается примитивным инстинктом.
Definitions
A basic, inherent drive or impulse that is fundamental to human or animal behavior, often related to survival, reproduction, and other essential functions.
Words
primitive

adjective
первобытный
instinct

noun
инстинкт