If the eyes are the windows to the soul, the eyebrows must surely be the frames, shaping the face and giving definition to the eyes and forehead. Many women spend a great deal of time maintaining the appearance of the eyebrows, via plucking and shaping, cosmetics, or even surgical implants. Historically, fashionable trends revolved around thickness, hue, and the shape of the arch; and there is no doubt that eyebrows have always contributed significantly to the perception of facial attractiveness.
However, compared with other primates, modern humans are relatively hairless, so the persistence of the eyebrow over time is curious.1 Do eyebrows merely represent evolutionary vestiges, or do they serve a greater, or more functional, purpose? Indeed, as one of the most powerful and versatile features of the human face, the eyebrow informs the perception of beauty and plays a critical role in sexual dimorphism, facial recognition, and non-verbal communication.
Muscular Anatomy of the Brow
The musculature of the brow has received intense study with the advent of brow treatments with neuromodulators and fillers. Three muscles—the corrugator supercilii, procerus, and depressor supercilii—work together to cause the head of the brow to rotate medially and descend in the frown.2 The frontalis, the primary elevator muscle, raises the forehead and eyebrows medially and can elevate the eyelid as high as 5 mm at maximal action.3 (Figure 1).
From the age of 25 in women and 45 in men, there is a progressive resorption of bone and fat in the periocular and perioral regions.4 For the first time in history, brow position can be affected by voluntary medical injection treatments,5 a trend that is summarized by the 4900.1% increase in injectable treatments seen from 1997 to 2012.6 (Figures 2a and 2b.)
Evolution of the Brow
The supraorbital ridge, also called the supraorbital arch or supraciliary ridge, lies above the eye sockets and is common to all primates, including humans, although the size of the ridge varies between species.7 Scientists refer to a more prominent ridge as the supraorbital torus, which presents as a continuous shelf of bone that projects above the orbits and nose and can be seen in our closest living relatives (the gorilla and chimpanzee), as well as in most fossil hominids (our ancestors). With the expansion of the cortex and development of the frontal lobe, the prominent brow gave way to the high, straight forehead of modern Homo sapiens, leaving behind only 2 hairy reminders of our evolutionary past along the lower margins of the ridge. What purpose do they serve?
Researchers believe the primary function of the eyebrow to be one of protection, the slope of the brow and arch drawing moisture or other debris around to the sides of the face. Because of their position and curvature, the eyebrows act as a shield against direct bright light, and stimulation of the hairs—abundantly innervated and sensitive to tactile stimulation—causes a reflex blinking of both eyelids.8 But why did nature select the emergence of eyebrows for extra protection over the maintenance of the supraorbital torus or prominent (and hairless) brow ridge? The answer may lie outside the scope of basic anatomy.
The Beautiful Brow
Like the hair on our head, our eyebrows, and in particular how we groom them, can say much about the time and place in which we live and have enormous influence on the perception of beauty and attractiveness. Over the centuries, eyebrows have been plucked into oblivion, shaved and repainted high on the forehead in bold slashes or delicate arches, removed and replaced with false eyebrows made from the fur of rodents or other animals, and attached with various types of glue.9 Ancient Egyptians shaved or tweezed their eyebrows and then darkened them with gray or black powder made from a lead-based mineral, and classical brows were painted black with soot or powdered minerals or affixed with false brows made out of dyed goat’s hair and tree resin. During medieval times in Europe, women favored skinny brows and plucked hairlines to achieve a high, domed forehead, a trend that continued into the reign of Queen Elizabeth I, when the pale, “egg-like” appearance denoted sexual and spiritual purity (Figure 3). Parents rubbed walnut oil into their children’s eyebrows in an effort to prevent the growth of hair. In China, the Ming Dynasty empresses were very aware of the age-related descent of the brow, so they shaved or plucked and carefully drew their brows back on but placed higher on their foreheads.9 (Figure 4).
In the seventeenth and eighteenth centuries, bold brows made a comeback as a symbol of youth. However, the same makeup used to whiten a good lady’s face and conceal unsightly pockmarks and pitting—ceruse, a mixture of white lead and vinegar—caused women to lose their eyebrows, among other unfortunate side effects.10 To compensate, women would trim scraps of mouse or rat pelts (caught from nightly traps) into glossy fake eyebrows that had a terrible habit of coming unglued at inopportune times.
In 1915, a young entrepreneur named Tom Lyle Williams watched his sister, Mabel, fix her singed eyebrows with a mixture of Vaseline, ash, and coal dust, and tried to recreate a similar product using petroleum, carbon black, cottonseed oil, and safflower oil.11 When his first effort with the chemistry set failed, he teamed up with drug manufacturer Parke-Davis, eventually marketing a scented, colorless cream with petroleum and oils that promised to nourish and promote the growth of eyelashes and eyebrows—although he noted that 2 to 3 boxes were needed before any noticeable improvement—under the name Maybell Laboratories. He later renamed his company Maybelline, and a world of cosmetics opened up.
Since then, eyebrow fashions have cycled through skinny vs fat, arched vs straight. Arresting, impeccably groomed eyebrows of the fifties followed the anorexic arches of the twenties, and were followed in turn by thick and thin versions over the years.9In the film and fashion world, eyebrows had become a unique calling card. Witness Audrey Hepburn’s dark, straight brows, the thick and sultry arches of Marilyn Monroe and Elizabeth Taylor, or Frida Khalo’s defiant uni-brow. Sophia Loren shaved her brows and drew them back in using excruciatingly detailed strokes.9 All of them were instantly recognizable.
Facial Recognition
It has always been assumed, and demonstrated, that facial recognition depends primarily on the eyes.12-14 In the sixties, Professor Desmond Morris studied eye movement recordings demonstrating that the observer’s line of sight roves from the subject’s periocular region down to their mouth, and back up to the area of the eye.15 His studies emphasized the importance of the interpersonal analysis of the emotional and social context of a face.
Historically, the brow ridge in the periocular region may have been an important sexually distinctive characteristic of our early ancestors’ faces: with higher levels of testosterone, men naturally have more pronounced brow ridges and eyebrows, angular jaws, and thick facial hair. Recent studies have found an important role for eyebrows in discriminating between male and female faces. Bruce and colleagues found that eyebrow thickness and position aid in gender differentiation, with thinner brows that are higher above the eye for women compared with men.16,17 Prior studies examining the key markers of facial recognition identified a hierarchy of key identifying features, with the eyes as the most important, followed by the mouth and the nose.12-14 Eyebrows were disregarded entirely or grouped together with the eyes.13 However, a more recent study demonstrates that the absence of eyebrows significantly impairs the ability to recognize familiar faces to a greater degree than the absence of eyes.18 Sadr and colleagues altered 50 photographs of celebrities using a feature omission technique in which the eyes (25 images) or eyebrows (25 images) were digitally removed while retaining the color and texture of the skin for minimal visual disruption.18 Eighteen subjects examined photographs from each set and were able to recognize 55.8% of images without eyes, but only 46.3% without eyebrows.
Communication and Emotional Response
No other feature of the face is so easily modified or so powerful as a visual form of communication. Throughout history, eyebrows have had the uncanny ability to demonstrate much without saying a word. Consider the exaggerated arches of the silent film stars like Greta Garbo that conveyed every twitch of emotion on camera. Those brows were serious; those brows were meant to speak in the absence of voice. As research has shown, eyebrows are a language unto themselves.
Indeed, the position of the eyebrows—elevated, depressed, or drawn together, all dependent on the interplay of elevators and depressors—is critical for emotional expression. Changes to the angle, height, and curve of the eyebrow, alone or in combination with other facial movements, can produce a broad range of signals across the spectrum of human emotion that radically alter the expression of the face and serve as nonverbal forms of communication to convey emotion.18 Maximal elevation of the medial and lateral portions of the eyebrows results in a look of surprise, depression of the medial portion depicts anger or concern, and the raising of a single eyebrow denotes a quizzical or questioning expression.8
Ekman and Friesan, pioneers in the measurement of facial expression, compartmentalized the face into 3 regions—upper (eyebrows, forehead), middle (eyes, cheekbones), and lower (mouth, nose, and chin)—and found that the eyebrows play a key role in the expression of a number of universal emotions, including happiness, surprise, and anger.19-23 Moreover, of the 7 visibly distinctive eyebrow actions, 5 are involved in emotional expressions, while the other 2 play a major role in a variety of conversational signals, whether on the part of the speaker or listener.22 In American Sign Language, a signed statement automatically becomes a question with the addition of raised eyebrows.24 The eyebrow flash is a universally recognized, yet unconscious, social signal across all primates and cultures, comprising a quick (approximately one-sixth of a second) upand- down movement in recognition and greeting, preparing the user (and receiver) for social contact.25 Similarly, raised eyebrows during speech can signal questions, emphasize or accentuate a word or phrase, and serve as punctuation, while the brow movements of a listener may denote seriousness, importance, doubt, perplexity, or difficulty in comprehension, among other signals.18
Conclusion
Eyebrow fashions change with the ages. In ancient Egypt, both men and women displayed natural full eyebrows. In the Middle Ages in Europe, in the age of Chivalry, the brow was seen to be important sexually, and it became fashionable for attractive women to shave or pluck their eyebrows as well as their anterior hairline to produce a pale, egg-like appearance considered appropriately demure. In the last 100 years, women have commonly altered or enhanced the shape of the eyebrows by plucking them into fine arches, a trend currently considered unnatural. Brow experts teach women how to shape their eyebrows for a fuller and more youthful look, aided by topical hair-growth products, cosmetic powders, pencils, tattoos, and even transplants.
Throughout history, the appearance of the brow has always been important, but recent research has shown that the role of the eyebrow in emotional expression defines dominance, emotion, gender, or adherence to modern fashion. It may be argued that today the brows have a greater social significance as powerful markers of facial recognition and multipurpose signalers, able to communicate a wide range of emotion and messages, to amplify verbal messages, or, even better, to communicate without saying a word.
Source: Carruthers, J., & Carruthers, A. (2014). Social significance of the eyebrows and periorbital complex. Journal of drugs in dermatology: JDD, 13(1 Suppl), s7-s11. Content and images used with permission from the Journal of Drugs in Dermatology. Adapted from original article for length and style.
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