Acharya Prashant explains that a child's fear of the dark is not learned from the environment but is an ancient, biological instinct. This fear dates back hundreds of thousands of years to when humans lived in jungles and were vulnerable to nocturnal predators. Because human eyes cannot see in the dark, the night was a time of great danger, and this terror became hardwired into our cells and brain. Even without any specific education or negative experiences, a child will naturally develop this fear as they grow, typically becoming more apparent around the age of two to four years.