Acharya Prashant explains that fear is a biological instinct ingrained in the human body through millions of years of evolution. Using the example of extinct Australian animals that failed to fear humans, he illustrates that while fear was once essential for physical survival in the jungle, it has now become a laggard. Evolution is a slow learner and an even slower unlearner; consequently, humans continue to experience primitive fears, such as the fear of the dark, despite modern advancements like electricity. This evolutionary laziness causes humans to remain wedded to bodily impulses that are no longer relevant or useful in a modern context.