The shape of the human nose, including whether its tip points slightly upward, is a distinctive facial feature that varies significantly among individuals. An upturned nose, sometimes called a “celestial nose” or “pixie nose,” is characterized by a tip that angles upward, often making the nostrils more visible from the front.
The Role of Genetics
An individual’s nose shape, including the angle of its tip, is largely determined by the genetic information inherited from both parents. This inheritance is not controlled by a single gene but rather by a complex interaction of multiple genes, a phenomenon known as polygenic inheritance. Each gene contributes a small influence to the overall outcome.
While research continues to identify all specific genes involved, studies have linked certain genes to particular aspects of nose shape. For instance, the gene DCHS2 has been found to influence how far the nose protrudes, whether it is upturned, and the angle of the tip. Other genes, such as GLI3 and PAX1, affect nostril breadth, while RUNX2 influences the width of the nose bridge. These genes play roles in cartilage and bone development.
Ancestry and Population Variation
Nose shapes exhibit considerable variation across different human populations and ancestral groups. This diversity arises from historical patterns of migration, genetic drift, and shared ancestry among communities.
Populations that have historically intermarried within their communities or remained geographically isolated often developed distinct genetic profiles. These unique genetic blueprints can manifest in shared physical traits, such as the shape of the nose. For instance, noses of African descent often feature wider nostrils and a broader nasal base, while Caucasian noses typically have a higher nasal bridge and narrower nostrils. Asian noses often present with a flatter bridge and a more rounded tip.
Developmental Changes
The nose undergoes significant changes in shape and proportion from embryonic development through adulthood. While the basic structure is genetically determined before birth, the nose continues to grow and mature throughout a person’s life. During embryonic development, the nasal placodes form, deepening into nasal pits and eventually leading to the formation of the nasal cavity and septum.
From infancy through adolescence, the bones and cartilage that form the nose develop, contributing to its definition. The nose grows rapidly in the first few years of life, then slows down, with a second growth spurt occurring during puberty. Girls typically reach their adult nose size by 15 or 16, while boys do so by 18. As individuals age, the nose can appear to change further due to factors like weakening skin and cartilage, which might lead to the tip drooping or the nose appearing longer.
Evolutionary Explanations
The diversity of human nose shapes, including features like an upturned tip, is thought to have broader evolutionary underpinnings. One prominent theory suggests that nose shape evolved as an adaptation to different climates. The nose plays a crucial role in conditioning inhaled air by warming and moistening it before it reaches the lungs.
Wider nostrils and broader noses are more commonly found in populations whose ancestors lived in warm, humid climates, as these shapes allow for greater airflow with less effort. Conversely, narrower and longer noses, often with more projection, are more prevalent in populations from colder, drier environments. These nasal structures are thought to be more efficient at trapping and warming cold, dry air, thus protecting the respiratory system.
This concept, sometimes referred to as Thomson’s nose rule, highlights how environmental pressures likely influenced the natural selection of specific nasal anatomies over generations. Beyond environmental adaptation, sexual selection may also have played a role, where certain facial features, possibly including specific nose shapes, were perceived as attractive by mates, leading to their increased prevalence over time.