Animals, if you think of the standard picture of a cow, they first of all spend a lot of time wandering around, chewing grass, which is tough. And then they have stomachs and they spend much of the day digesting this food. It takes a huge amount of energy to digest food. So that when you cook, what you are essentially doing is outsourcing digesting–chewing and digesting–into the kitchen. And doing it previously. And that saves a lot of energy for the humans who are lucky enough to eat the cooked food. Of course, the energy has to come from somewhere, and part of it is from the thermal energy of the fire; but part of it is from the energy of the people or animals or later on wind or water or steam that are doing the hard work of grinding.
Rachel Laudan on the History of Food and Cuisine, EconTalk, 17 August 2015
Added to diary 15 January 2018