From an evolutionary perspective, beauty is a gauge to measure fitness and suitability of a mate. Attractive facial features may signal sexual maturity and fertility, emotional expressiveness, or confer a cuteness that evokes a protective instinct.⁶ As a “survival-of-the-fittest” instinct, avoidance of deformity and disease directs us toward mates who exude health and vitality. Symmetrical features, healthy bodies, and flawless skin are idealized. These parameters are commonly used to define physical beauty—but they also leave room for variability and interpretation.

There is clear agreement that attractiveness ratings are similar in a number of cross-cultural studies.^7,8 When considering the genetic angle of defined beauty, men are attracted to delicate jaws, large eyes, narrow waists, and full hips and lips, probably because these features signal youth and a high estrogen level, which in turn means fertility and fecundity. Women, on the other hand, are attracted to strong chins, height, broad shoulders and wide jaws, probably because they signal a high testosterone level and imply an ability to protect and feed a family.^9,10

The pursuit of beauty is a basic instinct and a biological adaptation to help ensure the survival of our genes and, in a sense, ourselves. Research suggests that sensitivity to beauty is due to an instinct that has been shaped by natural selection.¹¹ For example, certain studies show that infants will stare significantly longer at faces deemed by adults to be attractive.¹² In addition, mothers of attractive newborns spend more time interacting with their babies. Studies have also shown a disproportionate number of abused children may not fit the standard canons for beauty.¹²

In other words, beautiful people are excused for everything from stupidity to serious crimes. People are more likely to help the good-looking (even if they dislike them) and are less likely to ask them for help.^13,14,15 A common theory even has it that beauty is the appearance of things and people that are good, meaning attractive people are judged more worthy simply because of their looks.
Beauty clearly brings ease. It is, as they say, its own reward.¹⁴

Anatomical beauty is relatively easy to define and measure. Population surveys have identified the facial features that contribute to a generalized ideal. These include a full head of hair, smooth complexion, large eyes, small nose, full lips, slightly protrusive lower face, and high cheekbones. On the other hand, facial features that detract from beauty are disproportion, asymmetry, excessive size, convexity of profile, retrusion of the chin, skin laxity, thin lips, large nose, and irregular or discolored teeth.¹⁶

Historical tools or parameters used to measure facial aesthetics include the golden aesthetic proportions, neoclassical canons of facial proportion, the Frankfort horizontal plane, and facial shapes (Table 1-1).

The Greeks were fascinated by beauty as conveyed by the pursuit of godlike perfection in their statues. They also considered mathematics to be the unifying basis of life, art, the gods, and the universe. It is therefore no surprise that they tried to define beauty with mathematics. The divine proportion, or “golden section,” was taken up by Plato as a mathematical relationship expressing universal harmony. Considered an ideal measure to govern the relationship of elements of the human body, it is expressed as 1:1.618, a ratio that occurs in many natural forms such as plants, shells, and snowflakes. Leonardo da Vinci later used the “golden section” in his portraits. The apparent importance of the ratio led Ricketts, an orthodontist, in 1982 to postulate a divine proportion for facial analysis.¹⁷ This concept is believed to have originated with the sculptor Phidias, hence the expression phi in relation to the golden proportion, which has been used as an aesthetically pleasing relationship of vertical and/or horizontal structures. Ricketts indicated that this relationship seems to occur naturally in a variety of guises in the human face and body. However, in 1992, Davis and Jahnke disputed the relevance of the “golden section.” They demonstrated a preference for internal facial divisions with a unitary value with bilateral symmetry.¹⁸

The neoclassical canons of facial proportions, described by scholars and artists of the Renaissance based on classical Greek canons, are still used for evaluation of facial features today (Table 1-1). Standard canons include the division of the face profile into thirds, with the height from the hairline to the eyebrow, from the brow to the lower edge of the nostril, and from the nostril to the chin being equal (Fig. 1-3). Other guidelines state that the height of the nose and the ear be the same, the width of the mouth be one and a half times the width of the nose, and the inclination of the nose bridge be parallel to the axis of the ear.

In 1985, Farkas et al. suggested that the facial canons did not work well when used to measure beauty in contemporary white subjects.¹⁹ How would the canons perform

across ethnic boundaries? Matory assessed the applicability of various parameters of attractiveness in 400 “attractive” subjects representing different ethnic and racial groups: black Americans, Hispanic, Asian, Middle Eastern, and Caucasian.²⁰ The neoclassical canons were inconsistent in each of the ethnic categories. The face could be divided into three equal parts, and the face and cranium into four equal parts, in fewer than 9% and 4% of individuals, respectively.