I'm not sure there has to be just one "smartest person in the room"; people have different fields of expertise, so it's almost always possible to learn something from someone. You can be a mentor in one thing and a student in another if the room has a sufficiently diverse group of people.
The way I see it, the smart people can both:
- Satisfy their intellectual curiosity individually through their work or in personal extracurricular activities
- Establish a mentoring relationship with the rest of the group
Regarding the second option, I believe this is a healthy group dynamic. It raises the groups average IQ or expertise, and training / mentoring others helps to solidify your own understanding of a subject. Perhaps in time the mentee will get to the point where they can challenge and expand the mentor's own understanding.