The talk about the mechanics of evolution I gave yesterday went very well, and I looked at the factors that shaped our body (walking on two legs, the hands, the voice box, and loosing hair) when we moved from the African forests to the savannah. I then discussed why a brain is very expensive - and why animals would not evolve a large brain unless there was a very real advantage. I then discussed how a rudimentary language, a tool-making culture, and a bigger brain could lead to the kind of explosion in apparent human intelligence (as judged by surviving artifacts) that started sometime between 50,000 and 100,000 years ago.
If you need to prepare a similar talk, aimed at a lay audience, you may find the slides of the talk (pdf file) helpful. Most should be reasonably self explanatory apart from a few slides at the end which very briefly look at a model of how the brain uses memories to make decisions - which relates to some of my own research. A more detailed paper will appear on this blog shortly.