In 2008, touring America to promote The God Delusion, I spoke to a large audience at the University of California at Berkeley. It was a nostalgic visit for me, as I had spent two eventful years there as a young man. Today I stand by everything I said in the lecture.

Why are there two sexes, and how is the balance between the two maintained in evolution? The riddle is one that baffled Chales Darwin. He explicitly left it for later generations. It was eventually solved, with typical brilliance, by the great Ronald Fisher. The fundamental sexual inequality is an economic one. Eggs are hugely larger than sperm. From this much follows. Why do peacocks have such a ridiculously large, ornamental “tail”, when it obviouly must put them in danger? Do females go for male beauty for beauty’s sake (as Darwin thought, and Fisher explained)? Or are males advertising some useful quality (as AlfredWallace, Darwin's co-discoverer of natural selection, insisted). Is the peacock’s tail favoured in spite of being a handicap? Or could it be favoured precisely becuse it is a costly handicap? Does it have to be costly as a certificate of honesty? Do females only go for honest males? This is a talk I gave on a ship crusing the Galapagos archipelago.

I filmed a conversation about death shortly after Dan Dennett recovered from a life-threatening condition. In addition to discussing personal mortality, we talked about bereavement. I thought this time it would be appropriate to listen again to his wisdom—the wisdom of a great thinker and a dear friend. Big books, was an eloquent speaker, had deep knowledge of science as well as philosophy, was a talented musician and sculptor, lived a full life and died in harness. It leaves a huge gap in the world of intellect, Dan, I will miss you so much, so deeply.