In such a brutal landscape, [Betty Meggers of the Smithsonian Institute] and other scientists contend, only small nomadic tribes could survive. (3.8)
This is a short line, but it shows a huge flaw in the thought processes of the time. By the end of the story, we'll be presented with a new theory that better explains the lifestyle of tribes in the Amazon. Just because Betty can't survive in the jungle doesn't mean no one else can.
"Monkeys are looked on as good eating," Fawcett observed. "Their meat tastes rather pleasant; but at first the idea revolted me because when stretched over a fire to burn off the hair they looked so horribly human." (8.28)
Part of surviving in the jungle is doing things you wouldn't normally want to do, like eating a monkey that looks like your cousin. Cannibalism starts to make a little more sense when you look at it this way.
It wasn't the big predators that he and his companions fretted about most. It was the ceaseless pests. (8.30)
If you don't like spiders, the Amazon is not the place for you. The bugs there are insane, including ticks, parasitic worms, mosquitos, and something called "kissing bugs" that leave your lips covered in welts. We haven't even gotten to the bugs that burrow into your eyeballs, because we passed out before those arrived.
Of all the Amazon's tricks, this was perhaps the most diabolical. As Fawcett put it, "Starvation sounds almost unbelievable in forest country, and yet it is only too likely to happen." (10.15)
In here is the secret to survival in the Amazon: knowing how to find food. There's no Whole Foods on the banks of the Amazon, but hey, there sure are plenty of organic piranha to fish for. Mind the teeth.
A polar explorer has to endure temperatures of nearly a hundred degrees below zero, and the same terrors over and over: frostbite, crevices in the ice, and scurvy. […] In contrast, an Amazon explorer, immersed in a cauldron of heat, has his senses constantly assaulted. (12.25)
Earth has many different environments. You need different survival skills to survive in the Antarctic from those you need to survive in the Amazon.
"As to missing various phases of civilized life, one has no time to miss anything save food or sleep or rest. In short one becomes little more than a rational animal." (12.38)
A biologist writes this, and it's a good way of explaining why the tribes in the Amazon seem so "primitive." Modern people have the luxury of leisure time and entertainment, but people in the Amazon must spend 99.9% of their time on survival. Some anthropologists have challenged this idea—some tribes only really work a few hours a day, and they do just fine—but we get the point.
Fawcett, quoting a companion, wrote that cannibalism, "at least provides a reasonable motive for killing a man, which is more than you can say for civilized warfare." (17.15)
Fawcett delivers a killer anti-war burn. This quote also explains why Fawcett feels more at home in the jungle than in the so-called "civilized" world. In the jungle, at least life makes sense.
Colleagues had once doubted his theory of Z largely for biological reasons: the Indians were physically incapable of constructing a complex civilization. Now many of the new breed of scientists doubted him for environment reasons: the physical landscape of the Amazon was too inhospitable for primitive tribes to construct any sort of sophisticated society. (17.37)
Fawcett's expedition is always being doubted for various reasons. However, most of the people who doubt him haven't gone in and got down and dirty in the way Fawcett has. The person to trust is the person who has lived through it.
"The place was so beautiful, and now it is gone. And I ask a man working there, 'What are you doing?' He says, 'We are building a hydroelectric dam.'" (23.34)
As the book ends, we see a change in the natural landscape of the Amazon. It's still being used and abused by Western "civilization." Surprise, surprise. Now that the Amazon has been explored, people are cutting down trees and changing the environment. It hurts the tribes and changes their way of life. And wrecks the entire planet, just for good measure. But, hey—profits.
I walked for an hour, and there was still no sight of anyone. The box on my shoulder had grown heavier, as had the bag for my laptop, which, among the mangroves, seemed like an absurdity of modern travel. I thought about leaving them behind, but there was no dry spot to be found. (25.32)
Grann enters the jungle with a lot of fancy technology. Here, for about an hour, he has to survive the way Fawcett did, without any of those luxuries. Grann realizes how difficult Fawcett's trials were…and he probably realizes that he himself wouldn't be a good contestant on Survivor.