Evolved Human Behaviors: Nonverbal Communication
Facial Expressions
Many facial expressions have been identified as having an innate basis in humans.
The evidence for this assertion comes from three lines of evidence:
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Smiling by a chimp and similarity between chimp and human expressions
Existence of the trait in physically handicapped children. Play faces are also seen in blind or deaf-blind children. How could they show this expression without ever seeing it unless the trait were innate? Examples of play faces can be seen in a blind infant and deaf-blind 7-year old:

Play faces by a blind infant and deaf-blind child.
Cross-cultural studies. If a behavior is exhibited across all cultures studied, the assumption is that it is innate. One of the first examples of a behavior fitting these characteristics is the eyebrow flash (Figure 2). The eyebrow flash serves as a recognition signal and as an invitation for interaction. Watch an Eyebrow Flash (from the Human Ethology Film Archives). See also a Himba flash.
Other facial expressions that are seen cross-culturally (many of which are also seen in non-human primates) include expressions of anger and rage (Fig 3), worry or anxiety (Fig 4), and fear faces (Fig 5). An anger face is characterized by the lips tightly drawn across the teeth. Interestingly, there are gender differences in the ability of males and females to read these emotions, with females more capable (more on this is here). With rage, the lips are so tightly drawn over the teeth that the teeth are exposed. Fear faces are characterized by the cheeks tightly drawn back so that side teeth are exposed. The corners of the mouth by be drawn up (almost like a smile), or down).
Coy or flirtatious behavior is also seen across cultures (Fig 6). Typically, the female looks sideways at the male until she catches his attention, Then she turns away and down with a smile, usually while maintaining eye contact. She then turns again toward the male, shows a full smile, but either covers it with her hand or by looking down. These behavior patterns are only seen in females and show up very early in their development. You can watch an example of coy behavior here (from the Human Ethology Film Archives). The intensity of the coy or flirtatious behavior can be intensified with the use of a pout (fig 7). Again, these behaviors are not seen in males. Other examples of female flirtatious behavior is here.
Body language and gestures.
Body language and gestures can also be used for communicating emotional states.
These gestures are seen cross-culturally around the world. A few are also seen in
non-human primates.
Some video clips of gesticulation are here.
Required Reading on the gestural origins of human language.