EXCERPT In the eighteenth century egg-roasting was a sufficiently puzzling activity that it inspired a familiar saying, ‘There is reason in the roasting of eggs’. The aphorism was intended to justify the most arcane of pursuits, but actually the reason for roasting eggs has been unknown until recently. There is indeed a good nutritional explanation for this now-vanished culinary tradition, as there is for cooking any other food: cooked food gives us more energy than we would get by eating the same food raw. Furthermore, our consumption of cooked food makes possible not just our high energy budgets, but also the extreme size of our brains. Accordingly the notion of ‘reason in the roasting of eggs’ includes a second meaning beyond the assertion of mere utility. It encapsulates my claim that the evolution of human mental powers has depended on our ancestors’ food being cooked…