Face

In an article published in 2018, researchers Kaoru Usui and Masayoshi Tokita note that "Mammals have evolved diverse morphologies to adapt to a wide range of ecological niches. The morphological diversity of mammalian heads is especially remarkable, possibly due to the head’s fundamental role in sensing, communication, and feeding." Such diversity is especially notable in primates, including human beings.

Notable elements of primate facial morphology include forward-facing eyes, which allow for binocular vision and depth perception, and a reduced snout and nose. The human chin is unique to homo sapiens, a characteristic that sets modern humans apart from other humanoid species such as Neanderthals. That facial structure and its underlying musculature enable the human face to convey a wide range of emotions and meanings and help humans to find similarities in familial and cultural groups. On the other hand, surface differences in faces among individuals and groups such as eye color and hair color, facial hair or the lack of it, skin color, and the size and shape of features such as eyebrows, noses, and mouths, as well as signs of physical deformity or damage, may also contribute to racist ideologies and social and political discrimination.

Human face

Structure

The front of the human head is called the face. It includes several distinct areas, of which the main features are:

• The forehead, comprising the skin beneath the hairline, bordered laterally by the temples and inferiorly by eyebrows and ears
• The eyes, sitting in the orbit and protected by eyelids and eyelashes
• The distinctive human nose shape, nostrils, and nasal septum
• The cheeks, covering the maxilla and mandible (or jaw), the extremity of which is the chin
• The mouth, with the upper lip divided by the philtrum, sometimes revealing the teeth

Facial function

Facial appearance is vital for human recognition and communication. Facial muscles in humans allow expression of emotions.

The face is itself a highly sensitive region of the human body and its expression may change when the brain is stimulated by any of the many human senses, such as touch, temperature, smell, taste, hearing, movement, hunger, or visual stimuli.

Facial variability

The face is the feature which best distinguishes a person. Specialized regions of the human brain, such as the fusiform face area (FFA), enable facial recognition; when these are damaged, it may be impossible to recognize faces even of intimate family members. The pattern of specific organs, such as the eyes, or of parts of them, is used in biometric identification to uniquely identify individuals.

Facial shape

The shape of the face is influenced by the bone structure of the skull, and each face is unique through the anatomical variation present in the bones of the viscerocranium (and neurocranium). The bones involved in shaping the face are mainly the maxilla, mandible, nasal bone, zygomatic bone, and frontal bone. Also important are various soft tissues, such as fat, hair and skin (of which color may vary).

The face changes over time, and some features common in children or babies disappear over time, such as prominent buccal fat pads, whose role in the infant is to stabilize the cheeks during suckling. While the buccal fat pads often diminish in size, the prominence of bones increase with age as they grow and develop.

Facial shape – such as facial symmetry – is an important determinant of beauty.

Other characteristics

Visible variable features of the face other than shapes and proportions include color (paleness, suntan and genetic default pigmentation), hair (length, color, loss, graying), wrinkles, facial hair (e.g. beards), skin sagging, discolorations (dark spots, freckles and eye circles), pore-variabilities, skin blemishes (pimples, scars, burn marks). Many of these features can also vary over time due to aging, skin care, nutrition, the exposome (such as harmful substances of the general environment, workplace and cosmetics), psychological factors, and behavior (such as smoking, sleep, physical activity and sun damage).

Mechanisms underlying these include changes related to peptides (notably collagen), inflammation, production of various proteins (notably elastin and other ECM proteins), the structure of subcutaneous tissue, hormones, fibers (such as elastic fibers or elasticity) and the skin barrier.

The desire of many to look young for their age and/or attractive has led to the establishment of a large cosmetics industry, which is largely concerned with make-up that is applied on top of the skin (topically) to temporarily change appearance but it or dermatology also develop anti-aging products (and related products and procedures) that in some cases affect underlying biology and are partly applied preventively. Facial traits are also used in biometrics and there have been attempts at reproducible quantifications. Skin health is considered a major factor in human well-being and the perception of health in humans.

Genetics

Genes are a major factor in the particular appearance of a person's face with the high similarity of faces of identical twins indicating that most of facial variability is determined genetically.

Studies have identified genes and gene regions determining face shape and differences in various facial features. A 2021 study found that a version of a gene associated with lip thickness – possibly selected for due to adaption to cold climate via fat distribution – introgressed from ancient humans – Denisovans – into the modern humans Native Americans. Another study found look-alike humans (doppelgängers) have genetic similarities, sharing genes affecting not only the face but also some phenotypes of physique and behavior. A study identified genes controlling the shape of the nose and chin. Biological databases may be used to aggregate and discover associations between facial phenotypes and genes.