Paul said he wanted to talk about "involution". I had no idea what he meant, but I was willing to along with it because Paul Levy tends to have interesting things to talk about.
Involution means the opposite of evolution. If evolution is about the fittest surviving, about decisions being taken by those who show up, about rewarding winners, then involution is about taking the time to look at those ideas and content that didn't make it, those people who aren't there ... and reflecting on what that tells us and what value we can get from them.
It's a useful technique in brainstorming in particular, but also in the facilitation of meetings and decision making, as well as part of "the humble facilitator's" approach to training and other learning workshops.