The Human Nose Is Unlike Other: Why They Stick Out

Humans are a curious species, not just because of our complex behaviors and advanced technologies but also because of our unique physical characteristics that set us apart from our closest primate relatives. One such characteristic is the human nose.

Unlike the noses of other primates, which are relatively flat and wide, the human nose protrudes outward in various shapes and sizes. This distinctive feature led to a plethora of hypotheses surrounding its evolutionary origin.

But what could explain this peculiar aspect of human anatomy?

Upright Walking

Understanding the prominence of the human nose begins with another hallmark of human evolution: bipedalism, or walking on two legs. This significant shift from quadrupedalism (walking on all fours) brought about a cascade of anatomical changes, particularly in the spine and skull.

The transition to an upright posture necessitated an S-shaped spine curvature, different from the relatively straight spine of quadrupedal mammals. This change not only allowed for balance and locomotion on two legs but also had profound implications for the human skull, specifically the foramen magnum—the opening at the base of the skull where the brainstem meets the spinal cord.

As humans evolved to walk upright, the position of the foramen magnum shifted forward to accommodate a forward-facing gaze while maintaining an upright posture. This repositioning led to a compression of the splanchnocranium, the lower part of the skull that includes the jaw and nose, relative to the neurocranium, which houses the brain.

This compression reduced the protrusion of the jaw and lower face, setting the stage for the development of our characteristic nasal prominence.¹

Diet & Jaw Size

The evolution of the human diet from primarily plant-based to include more meat played a significant role in the changing structure of our jaws.

The robust jaws and large molars of early hominins like Australopithecus were well-suited for grinding tough plant materials. However, as humans began to hunt and consume meat, the physical demands on our jaws decreased.

The advent of cooking further softened our food, reducing the need for large jaws and teeth. This dietary shift allowed our jaws to become smaller and less pronounced, contributing to the relative prominence of the human nose.²

Brain Expansion & Its Effects

Another critical factor in the evolution of the human nose is the significant increase in brain size among early humans.

As our ancestors faced new intellectual challenges, including the complexities of bipedal locomotion, their brains grew in size. This expansion of the neurocranium could have exerted outward pressure on the splanchnocranium, further emphasizing the nose’s protrusion.

The Nose as a Radiator

The idea of the nose acting as a radiator is particularly intriguing. With its intricate network of blood vessels, the human nose could effectively exchange heat, cooling the blood that circulates to the brain.

This theory suggests that the human nose not only serves an aesthetic and olfactory function but also plays a crucial role in thermoregulation, especially given the increased metabolic demands of a larger brain.

More Than Just a Snout

The human nose, often dismissed as a mere facial feature, is a testament to millions of years of evolution.

Its prominence is not the result of a direct evolutionary aim but rather a side effect of numerous anatomical and environmental adaptations, from the restructuring of our skulls due to bipedalism to the demands of a changing diet and expanding brain.

Beyond its role in breathing and smelling, the human nose may also contribute to our brain’s thermal regulation, showcasing the interconnectedness of our body’s systems.

Sources:

1. news.utexas.edu/2017/03/17/human-skull-evolved-along-with-two-legged-walking-study/
2. smithsonianmag.com/smart-news/how-dawn-farming-changed-our-mouths-worst-180954167/