The anger face: brows pulled down, upper and lower eyelids pulled up, lips rolled in and tightened. No matter where you go in the world, the facial expression of anger is expressed universally across all people of all cultures. Anger is one of the seven basic emotions along with sadness, happiness, contempt, disgust, fear and surprise.

The expression of anger is made by individuals who have been blind since birth, a fact used by psychologists to argue that this emotion (as well as the other basic emotions) are innate rather than learned. New research now suggests that anger serves a specific purpose: on its own, each aspect of the anger face may make its wearer physically stronger.

As mentioned in The Atlantic, “a study recently published in the journal Evolution and Human Behavior, Dr. Aaron Sell of Griffith University in Australia and his colleagues from UC Santa Barbara tested the effect of each feature of the anger face on a person’s overall appearance, using seven previously identified components of anger: Along with changes to the nostrils, lips, and chin, the brow and brow ridge both lower and the cheekbones and mouth both raise.

Starting from a computer-simulated image of a 20-year-old man, the researchers created pairs of faces for each of the seven features—one face neutral, one face with the anger-related change—and asked volunteers to assess each one for physical strength. Across the board, the faces with a single feature activated—neutral except for flared nostrils, for example—were rated as belonging to stronger men.

One reason for this link, Sell says, may be because of the increased leverage that fighting ability afforded our ancestors in resolving conflicts of interest: The more physically threatening a person looked, the more bargaining power they had to influence the outcome of a given situation. “The reason natural selection designed [the anger face] is that the individuals who made that face out-reproduced the other ones,” he explains. “And they out-reproduced them because the people who made that face won their conflicts. The other people backed down because they looked at them and thought, ‘Wow, he looks really tough.’”

The concept of aggression as an assertion of the upper hand has been well-documented in scientific literature, and anger faces are thought to be more easily identified than other expressions of emotion, allowing for more efficient responses to perceived threats. Previous research from Sell has also found that both genders can more readily identify expressions of anger on men—who are more likely to be aggressors, evolutionarily speaking—than on women, and that men with greater upper-body strength and more attractive women—two groups that, in the early days of humanity, would have had increased bargaining power—may also be quicker to anger than their weaker or less attractive peers”.

For more information on the evolutionary vestige of the anger face as well as all the other seven basic emotions, take a look at our MiX Professional and MiX Elite online training programs.