Fallen into a Beast

What is the difference between man and beast? It has a complex language system, rich emotional thinking, a strong self-awareness to suppress instincts, restrains oneself with morality and law, and integrates into the group. If one day, the world forces people to abandon their emotions and morality and stay loyal to their instincts and desires, will you choose to maintain your cognition as a human being or degenerate into a beast?