According to this theory [environmental determinism], even if some early humans eked out an existence in the harshest conditions on the planet, they rarely advanced beyond a few primitive tribes. Society, in other words, is a captive of geography.
-- Author (Preface paragraph 2)

Importance: This quote captures a solid definition of environmental determinism, the main scientific theory that is challenged by Fawcett and the author.

Explorers are not, perhaps, the most promising people with whom to build a society. Indeed, some might say that explorers become explorers precisely because they have a streak of unsociability and a need to remove themselves at regular intervals as far as possible from their fellow men.
-- Unnamed Royal Geographical Society Member (chapter 5 paragraph 1)

Importance: This quote by an unnamed RGS Member could be a perfect description of Colonel Fawcett himself. It provides thoughtful examination of adventurous explorer types, warts and all.

(...) these accounts made me aware of how much of the discovery of the world was based...
-- Author (chapter 5 paragraph 1)