Charles Darwin theorized that emotions were biologically determined and universal to human culture in The Expression of the Emotions in Man and Animals. However, the more popularized belief during the 1950s was that facial expressions and their meanings were culturally determined through behavioural learning processes. More recently, beginning with Paul Eckman's work on facial expressions in the 1970's, it has become clear that the expression of emotion is culturally universal – evidence that emotions are innate. Other streams of evidence also point strongly in this direction.
Facial expression research found a high agreement across members of diverse cultures on selecting emotional labels that fit facial expressions. Expressions found to be universal included those for anger, disgust, fear, happiness, sadness, and surprise. However some emotions are exhibited according to culture-specific prescriptions about who can show which emotions to whom and when.
In the 1990s, Ekman expanded his list of basic emotions, including a range of positive and negative emotions that are not all encoded in facial muscles. The newly included emotions are: Amusement, Contempt, Contentment, Embarrassment, Excitement, Guilt, Pride in achievement, Relief, Satisfaction, Sensory pleasure, and Shame.
[above text adapted from Paul Ekman]
There are other strong reasons for believing that emotions are innate, notably the similar expressions of emotion in our relatives the social primates, and the clear anatomical and functional similarities between the brain regions associated with some emotions (such as fear) between humans and more distantly related animals such as rats.
While the continuity of emotion with other animals is consistent with the traditional view of emotions as primitive, many of our emotions relate to regulating social interactions, and are likely to be evolutionarily recent in origin. Several brain regions associated with emotion are significantly enlarged in humans compared to our primate relatives. Neurological evidence from humans who are unable to experience emotion (see Descartes' Error) shows that emotion, rather than being an undesirable evolutionary relic, is essential to normal human functioning. This is consistent with theories of the smart unconscious.