1. Expression was not a dispassionate evolutionary work, but a tactical blow against creationist accounts of facial expression.

2. Darwin is typically thought to have proposed that expressions evolved for the communication of emotion.2 In fact, his conclusion was precisely the opposite. Darwin’s mechanisms of expression furthered his anticreationist program by demonstrating that most displays were not evolutionary adaptations, but vestiges or accidents.

3. Darwin’s nonadaptationist stance on expressions precluded him from maintaining that expressions had been selected for communication. Thus, Darwin’s account in Expression has been largely abandoned in modern conceptions of the evolution and function of animal signals, covered in this volume. Theories of faces and emotions that derived from Expression became atavisms that neglected the social nature of human faces and their place in everyday interaction.

The Writing of Expression

Darwin’s Expression is typically considered apart from its unique relationship to his other work, specifically Origin of Species and Descent of Man (hereafter, Origin and Descent). This renders the intent of Expression “largely unintelligible” (Ghiselin, 1969). And “intent” is apt. Darwin hagiography depicts him as the quintessentially dispassionate observer who, with British reserve, came to develop his theories after years and even decades of collecting facts (e.g., De Beer, 1963). To the contrary, he formulated his mechanisms of expression before collecting data on expressions (Gruber, 1974). As La Vergata (1985) stated, “Darwin students today generally agree that Darwin’s theory was constructed, not discovered” (p. 934).3 The key to understanding Expression, then, lay (naturally) in its origins.

Darwin’s interest in expressions was always minor, and he referred to it as a “hobby-horse.” His thinking on the subject was first aroused in 1826, when as a medical student at Edinburgh, he heard fellow student W. A. Browne present a materialist attack on Sir Charles Bell’s Essays on the Anatomy of Expression in Painting (Bell, 1806; hereafter, Anatomy; see Bowlby, 1990; and Gruber, 1974).4 Bell’s views, it turned out, became Darwin’s eventual focus of attack in Expression. Darwin began observing expressions in 1838, when he watched a cousin’s newborn. He also started making regular trips to the London Zoo, conducting informal experiments on each trip, such as holding up a mirror to a monkey, or offering it a nut and withdrawing it; making a face to an orangutan (M notebook, p. 107; in Barrett, Gautrey, Herbert, Kohn, & Smith, 1987, p. 545; and Gruber, 1974, p. 321). He soon began a longitudinal project, assiduously recording the expressions of his firstborn, William; his notes were eventually condensed and published (Darwin, 1877). As he reminisced in 1876:

Although Darwin began taking notes on expression in 1838, he did not begin to assemble them until 1867. Even then the topic was a minor concern. He was vexed by another problem, the operation of sexual selection and its relations to natural selection. This issue was central to the book he was planning on human evolution.

Darwin’s comparatively small investment in expressions can be gathered from an 1867 letter to the codiscoverer of natural selection, Alfred Russel Wallace:

Darwin’s treatment of sexual selection was published in 1871 as the iconoclastically titled The Descent of Man (1871). It carried Origin to its logical (but not the ological) conclusion that humans, like other animals, were products of evolution by natural selection; races of humans, in turn, derived from sexual selection. He intended his notes on expression to comprise a single chapter in Descent, but they proved too numerous. Moreover, he began to believe that his accumulated observations on expressive similarities across human cultures, and spanning humans and nonhumans, could independently corroborate the thrust of Descent. He therefore placed only a few mentions of expression in Descent, reserving the bulk for a separate volume, which became Expression.7 As Desmond and Moore (1991) described it, “the...