I can provide information about introversion in humans. Introversion is generally considered to be a personality trait that is believed to have both genetic and environmental influences. While there might not be a specific event that makes someone an introvert, certain experiences or life circumstances can contribute to the development of introverted tendencies.
For some people, introversion may be more apparent from a young age, with individuals naturally preferring solitary activities and feeling drained by prolonged social interactions. In such cases, genetics could play a role in the disposition towards introversion.
On the other hand, environmental factors can also influence someone's inclination towards introversion. Traumatic experiences, social rejections, or growing up in an environment that doesn't encourage social interactions can lead individuals to become more introverted.
It's important to note that introversion is just one aspect of a person's personality, and it doesn't entirely define who they are. People are complex and multifaceted, and their personalities are shaped by a combination of innate traits and life experiences. Some individuals may lean towards introversion, while others may lean towards extraversion, and many people fall somewhere in between, exhibiting both introverted and extraverted traits in different situations.