Part of his program of research is to convince people that they should stop distinguishing cultural and biological evolution as separate and we need to think of it all as biological evolution. He has begun to pursue the idea that he calls the cultural brain hypothesis -- that the real driver in the expansion of human brains was a growing cumulative body of cultural information.
An example he gives is of fire and cooking. This is what he says:
Fire and cooking have been important selection pressures, but what often gets overlooked in understanding fire and cooking is that they're culturally transmitted -- we're terrible at making fires actually. We have no innate fire-making ability.Fascinating, slowly but surely, we are making better sense of how we evolved to be what we are today. I'd love to come back in 100,000 years time and see how evolution has further shaped us - of course if the human race has not long become extinct!
But once you got this idea for cooking and making fires to be culturally transmitted, then it created a whole new selection pressure that made our stomachs smaller, our teeth smaller, our gapes or holdings of our mouth smaller, it altered the length of our intestines. It had a whole bunch of downstream effects.