Who is Robert L. Trivers from The Selfish Gene and what is their importance?

Dawkins often quoted this Trivers, which is unusual because, according to the book jacket, he was only an Associate Professor of Biology at Harvard.

Research outside the Selfish Gene shows that Trivers is a Harvard graduate, who went into psychology after suffering a nervous breakdown. He earned a graduate degree without even getting a BA and went on to become a leading evolutionary biologist.