Published in 1872, The Expression of the Emotions in Man and Animals was one of the first scientific books to use photographs as empirical evidence. Darwin investigated whether emotional facial expressions (fear, rage, grief, joy, disgust) are arbitrary cultural conventions or biological, universal evolutionary traits.
By surveying missionaries and travelers across diverse human cultures, observing infants, studying psychiatric patients, and comparing human expressions with primates, dogs, and cats, Darwin proved that fundamental emotions share identical neuromuscular pathways worldwide.
He formulated three core explanatory principles: Serviceable Associated Habits, Antithesis, and the Direct Action of the Excited Nervous System.
In the 21st century, Darwin’s findings form the empirical bedrock for Paul Ekman’s universal micro-expressions and computer vision algorithms in affective computing and AI emotion detection.
