People of African descent tend to have wider noses because of climate adaptation. Over thousands of generations, natural selection shaped nose width to match the temperature and humidity of the environment where populations lived. In hot, humid climates like much of sub-Saharan Africa, wider nostrils were a better fit for efficient breathing, and that trait was passed down.
How Climate Shaped Nose Width
Your nose does more than smell. One of its primary jobs is conditioning the air you breathe, warming and moistening it before it reaches your lungs. In cold, dry climates, this job is harder. Narrower nostrils slow airflow and give the moist lining inside the nose more time to humidify and warm incoming air. People with narrower nostrils had a survival advantage in those environments, produced more offspring, and passed that trait forward.
In warm, humid climates, the air is already close to body temperature and already carries plenty of moisture. There’s no advantage to slowing airflow down. Wider nostrils allow air to move freely without restriction, making breathing easier during physical exertion in the heat. Over time, populations in tropical regions developed broader noses, while populations in cold northern regions developed narrower ones.
This pattern was first described in the late 1800s by the anatomist Arthur Thomson, and it’s still called Thomson’s Rule: long, thin noses tend to appear in dry, cold areas, while short, wide noses tend to appear in hot, humid areas. Modern research has confirmed and refined this idea. A study led by researchers at Penn State University found that nostril width is strongly correlated with both temperature and absolute humidity, and that the differences between populations are too large to be explained by random genetic drift alone. Natural selection was clearly involved.
Why Natural Selection, Not Just Chance
Genes shift randomly over time in any population, a process called genetic drift. But when researchers measured nostril width and nose base width across populations from different climates, the variation was greater than drift alone could produce. That’s a strong signal that the trait was actively selected for, meaning it gave a real survival or reproductive advantage in specific environments.
The correlation is specifically between nostril width and absolute humidity. Interestingly, nose height (how far the nose projects from the face) doesn’t show the same strong climate link. It’s the width of the base and nostrils that tracks most closely with the humidity of a population’s ancestral environment. More detailed studies looking at different structural parts of the nose found that the internal nasal chamber (the air-conditioning space inside the nose) also correlates with climate, reinforcing the idea that breathing efficiency drove these changes.
Sexual Selection Played a Role Too
Climate pressure wasn’t the only force at work. Researchers believe sexual selection reinforced the pattern. In any given population, people tend to find locally common facial features attractive. If wider noses were already common in a tropical population because they worked well for breathing, people in that population would also tend to prefer wider noses in a partner. The same would happen in reverse in cold-climate populations, where narrower noses were more common. Penn State geneticist Mark Shriver has noted that ecological selection and sexual selection likely reinforced each other, pushing nose shapes further apart across populations over time.
Nose Shape Varies Within Africa Too
It’s worth knowing that “African nose shape” is not one single thing. Africa is the most genetically diverse continent on Earth, and nose shape varies significantly across its regions. West African and Central African populations, who lived in some of the most humid tropical environments, tend to have the widest nasal bases. East African populations, many of whom lived at higher, cooler elevations, often have narrower and more projected noses. South African populations show their own distinct patterns as well, with research documenting clear morphological differences even among groups within the same country.
Studies using CT scans of South African populations found that Black South Africans had wider, more rounded nasal openings compared to white South Africans, whose nasal openings were narrower and more pear-shaped. But the Black South African populations studied were descendants of Bantu-speaking groups who migrated from Central and West Africa, carrying nose shapes adapted to those humid tropical climates with them. Other indigenous southern African groups, like the Khoisan, have their own distinct nasal features. The point is that nose width exists on a spectrum, shaped by the specific climate history of each population’s ancestors.
The Same Logic Applies Everywhere
This isn’t a story unique to African populations. The same evolutionary pressure shaped noses on every continent. Scandinavian and Northern European populations developed notably narrow, projected noses suited to frigid, dry air. Southeast Asian populations in tropical lowlands tend to have wider noses, similar to West African populations, because they faced similar humid conditions. Indigenous populations in the cold, dry Andes developed narrower nasal passages than those in the tropical Amazon lowlands, despite living on the same continent.
Nose shape is one of the clearest examples of how local climate left a visible mark on human anatomy. Wider noses in populations with African ancestry are the result of tens of thousands of years of adaptation to warm, humid environments, reinforced by mate preferences, and carried forward through migration and genetics long after people moved to different climates.