The Story of the Human Body: Evolution, Health and Disease

"Well Dan Lieberman puts the brain into the context of the body as a whole. He’s friends with Richard Wrangham, but I know they diverge on what exactly was the first factor that really allowed that steep increase in brain size in human evolution. Richard sticks to cooking with fire, while Dan argues that that happened too late and is pretty vocal about wider changes in the human body that also put us on our way to becoming what we are today. That includes the changes that allowed bipedality. A bipedal primate uses one-fourth as much energy to move around as a quadruped. Walking upright is slower, but it also costs less energy so it’s more effective, and he proposes that bipedality was really one of the first components allowing our ancestors to get more food in their day, simply because they could explore larger ranges. “A bipedal primate uses one-fourth as much energy to move around as a quadruped.” Put that together with other anatomical changes in the body that Lieberman explains in his book, like the changes to your gluteus maximus (your butt), your toes, your neck muscles and the position of your head, which all contribute to making human ancestors very good runners. And once you run you also gain access to this new strategy for getting food which is cooperative hunting, and that encourages developing new tools and also communicating across individuals which requires more processing power, so supposedly that would create a positive selective pressure for more neurons in the brain. You also become capable of getting more energy through hunting, through running down other animals, so he puts all those things together and makes a very good case for the beginning of human evolution and rapidly increasing brain size. It also gives an answer to the question of how come only humans cook, and not other primates, because there were all these other anatomical changes that happened to the ancestors of our species alone, and it’s only when all those changes come together that you have a species that is not only anatomically capable of standing on its feet, using its hands and affording enough neurons to actually have the processing power required, but you also have the technology developed along the way, and new problems to solve with it. In the rest of the book, he goes on to talk about how, in a modern context, where we live in houses, eat a less varied diet because of agriculture, use cars not our feet, have refrigerators with plenty of food, how these anatomical characteristics actually have consequences for our health. It’s a really fascinating book."