Many will question Bickerton's claim that only humans are capable of mental engagement with anything but the immediate present. However, the heart of his argument—that language did not evolve as a development from high intelligence but is instead what allowed that intelligence to develop at all—is undeniably compelling. Under this conception, the emergence of language, not just intelligence, was what allowed humans to conquer the world. In support, Bickerton notes that the appearance of modern civilization was preceded by eons by cultural stasis during which hominid brains were nevertheless increasing vastly in size, which suggests that something besides mere brain power created modern man. He also notes that if human-like intelligence allowed world domination, then at least some animals should by now have developed it, even without language. Instead, only humans can profoundly alter their surroundings, which suggests that language, the trait most unequivocally unique to humans, is indeed the key to our hegemony. Bickerton even equates language and thought, arguing that their foundation upon the same syntax leaves no motivation to separate them, and considers both to evidence a layer of abstract representation unique to humans. In turn, he proposes that this layer is able to “observe” the lower layer, thus creating “consciousness.” The uniqueness of consciousness to humans is thus explained by its roots in a layer of representation unique to humans.