But the main point is being active and talkative is just draining for introverts. They rarely receive energy from being with a lot of people hanging around them. And the small talks between all that party goers just don't make sense for introverts. However, they may have fun at those extroverted parties from time to time. An extrovert, on the other hand, feels great at the party. An extrovert feels happy when surrounded by a lot of loud people.
The Chicken or the Egg. Antibiotic Resistance.
The Immune System. Genetic Phylogeny.