Near are lakes. Round their shores file shadows black of cedargroves. Aroma rises, a strong hairgrowth of resin.
Brains are very costly. Right now, just sitting here, my brain (even though I’m not doing much other than talking) is consuming about 20- 25 percent of my resting metabolic rate. That’s an enormous amount of energy, and to pay for that, I need to eat quite a lot of calories a day, maybe about 600 calories a day, which back in the Paleolithic was quite a difficult amount of energy to acquire. So having a brain of 1,400 cubic centimeters, about the size of my brain, is a fairly recent event and very costly.
The idea then is at what point did our brains become so important that we got the idea that brain size and intelligence really mattered more than our bodies? I contend that the answer was never, and certainly not until the Industrial Revolution.
Why did brains get so big? There are a number of obvious reasons. One of them, of course, is for culture and for cooperation and language and various other means by which we can interact with each other, and certainly those are enormous advantages. If you think about other early humans like Neanderthals, their brains are as large or even larger than the typical brain size of human beings today. Surely those brains are so costly that there would have had to be a strong benefit to outweigh the costs. So cognition and intelligence and language and all of those important tasks that we do must have been very important.
We mustn’t forget that those individuals were also hunter-gatherers. They worked extremely hard every day to get a living. A typical hunter-gatherer has to walk between nine and 15 kilometers a day. A typical female might walk 9 kilometers a day, a typical male hunter-gatherer might walk 15 kilometers a day, and that’s every single day. That’s day-in, day-out, there’s no weekend, there’s no retirement, and you do that for your whole life. It’s about the distance if you walk from Washington, DC to LA every year. That’s how much walking hunter-gatherers did every single year.
