With only trivial exceptions, humans differ from all other animals in being able to evolve culturally by accumulating information, ideas, and best practices over time. Proto-humans may have had something resembling modern speech as far back as Homo ergaster, 1.8 million years ago, and Heidelberg Man—the shared ancestor of Neanderthals and modern humans—had hyoid bones that could produce speech sounds and inner ears that could probably have distinguished the sounds of conversational speech.1 However, the evolution of modern Homo sapiens in the past 150,000 years represents a revolution in this regard.
For tens of thousands of years, the transmission and storage of information depended entirely on speech and memory. The first unmistakable evidence for communication through material symbols goes back nearly a hundred thousand years, in the form of engraved fragments of ocher from Klasies River Cave 1 in South Africa.2 However, symbols of this kind remained not only rare but also very simple until about fifty thousand years ago, when they suddenly (by prehistoric standards, at least) become common wherever humans are found. Archaeologists often refer to this as “the big bang of human consciousness.”3