SOLVED. Humans are supposed to live for millennia [s]

[Jenn]

I never read this book, but a friend of mine described it years ago.

I don't know if this story is fantasy or science fiction. In it, it's discovered that humans are supposed to live for millenia, not just a century. When humans become old, they're supposed to eat a special root or herb or something that, once consumed, allows them to live for thousands of years. At some point in the story, humans fight over this root.

I don't know if what I've described here is central to the book or not.

Anyone recognize it?

[Dawn]

Protector

Has this idea. It's an underlying theme for the Ringworld series

[Jenn]

Yeah, I think that's it. Thanks!