The idea of transparency has a long history. In 1872, thirteen years after first presenting his famous treatise on evolution, Charles Darwin published The Expression of the Emotions in Man and Animals. Smiling and frowning and wrinkling our noses in disgust, he argued, were things that every human being did as part of evolutionary adaptation. Accurately and quickly communicating our emotions to one another was of such crucial importance to the survival of the human species, he argued, that the face had developed into a kind of billboard for the heart.
