Macrocosm: The Evolutionary Basis for Human Diversity

Andriy Onufriyenko

Whether you went to your nearest zoo, traveled on an African safari, or did a quick google search, all of the zebras, elephants, and giraffes you’d see would probably all look exactly the same. It seems like once you’ve seen one, you’ve kind of seen them all. At the same time, you can easily tell the difference between your family members, coworkers, and even random strangers. This is because humans are exceptionally skilled at recognizing facial distinctions. Whereas other animals use smell or sound to identify individuals, humans only need to look at each other.

We are one of the most diverse species in the world. With variations in skin tones, hair textures, eye and nose shapes, facial bone structures, cheek sizes, and so much more, it is no wonder we all look so different. Instead of celebrating these differences, we often stigmatize them. Time after time we have turned them into sources for exploitation and oppression: Nazi ideology of an Aryan master race, Hazara discrimination in Afghanistan, the enslavement of Africans, and Apartheid. These examples don’t even begin to scratch the surface. 

We like to believe that we’ve learned from our past mistakes, but current events say otherwise. With implicit racial bias and the Black Lives Matter movement finally taking center stage across the globe, people are finally beginning to push towards diversity. This doesn’t mean they haven’t been faced with some resistance, actually a lot of resistance. When people make arguments against diversification, they often fail to consider that the variation amongst humans is not accidental. For far too long physical differences have been used to create separation, but in reality they are what make us all equal. 

Natural Selection: The Architect of Diversity

Charles Darwin is often referred to as the father of evolution. In 1859, his book On the Origin of Species was published changing the way we understand our world forever. Darwin defined evolution as “descent with modification” –  all organisms around today descended from a single, common ancestor that was modified over several generations.

Evolution is driven by natural selection, the process by which individuals with heritable traits that increase their chances of survival in a given environment produce more offspring than individuals lacking those traits. The selective advantage these “favored” traits present allows them to increase in frequency from one generation to the next. It goes without saying that other evolutionary processes were also involved in the speciation that has resulted in such a vast diversity of organisms. However, none of it would be possible without natural selection.

ALL People Have Melanin

Take a look at the map of indigenous skin colors across the globe. What do you see? You probably noticed that populations near the equator have darker skin tones and that as you move towards the poles skin color gradually lightens. This creates a glorious color gradient put in place by design. 

Credit: Emmanuelle Bournay, UNEP/GRID-Arendal

Most people think that only individuals with darker skin tones have melanin. This is false. Actually, ALL people have melanin. The exception being those with albinism, a condition resulting from a mutation which prevents melanin synthesis. Melanin is the name given to the biological pigments that give our skin and hair its natural color. Melanin is produced and stored in specialized cells called melanocytes. Although everyone’s skin contains about the same number of melanocytes, the type and amount of melanin they produce determines our individual skin tones. There are two types of melanin directly linked to skin and hair coloration: eumelanin and pheomelanin. Individuals with higher levels of eumelanin have darker skin tones and those with more pheomelanin have fairer complexions.

Early humans lived near the equator where there was a selective advantage to having darker skin. This region is known for its warm climate and strong exposure to direct sunlight. The sun emits ultraviolet (UV) rays which are absorbed into our skin where they can cause serious damage. Overexposure to UV radiation can lead to premature aging, immune system suppression, and skin cancer. It can also have adverse effects on reproduction as prolonged exposure to UV leads to the degradation of folate in skin vessels. Folate, a B-vitamin, is essential for normal embryonic development and is necessary for healthy sperm production. Before they can cause any damage, eumelanin absorbs these harmful UV rays and converts them to heat. Kind of like built-in sunscreen.

As our ancestors began to migrate away from the equator, direct sun exposure was no longer an issue. Ironically, they were faced with the exact opposite problem. Areas at higher latitudes are exposed to less direct sunlight, so people living there had to worry about UV shortage. UV radiation is a double edged sword: although it can be harmful, it is also essential for human health. UV is critical for the synthesis of vitamin D which in return is essential for calcium absorption. Calcium is used to build bones and maintain a healthy immune system. Pheomelanin is less effective at absorbing UV rays allowing for more light penetration and vitamin D production. Humans would never have inhabited regions such as Europe and Asia if they did not evolve to have lighter skin tones because illnesses such as rickets would have ravished early settlers.

Led by The Nose

Recently I came across the concept of an ethnic rhinoplasty. It feels almost contradictory, having plastic surgery in many cases distorts the ‘ethnic’ features we were born with. The plastic surgeons who advertise this type of procedure tout it as a way to preserve one’s heritage while also perfecting their appearance. In reality an ethnic rhinoplasty is just a regular rhinoplasty with a fancy name.

In my family we often make jokes about getting a group discount on nose jobs. Growing up Middle Eastern, everyone I knew wanted to have plastic surgery to fix their ‘Arab nose’. Some did and others still have plans to. Middle Eastern noses are characterized by having a nasal hump and a bulbous, downward pointing tip. If we shave down the hump and adopt the coveted ‘ski slope’ tip, aren’t we also erasing our ethnic characteristics? People often want to change these features because society considers them unattractive. Secretly our noses echo the stories of our ancestors and the environments they lived in, something that by its very nature is beautiful. Scientists have been throwing out theories on the selective force behind variations in nose shape as far back as the 1800s. As part of what is now known as Thomson’s nose rule, anatomist and anthropologist Arthur Thomson (1858-1935) suggested that there is a direct link between nose shape and climate.

Our noses have multiple functions: they act as a first line of defense against microbes trying to invade our respiratory system, allow us to taste food more fully, and import air and scents from the environment. Before this air can make its way into our lungs, it must first be ‘conditioned’ so our noses filter, warm, and moisten it. For this reason, Thomson posited that people with ancestral ties to warm, humid areas were more likely to have shorter and wider noses than those with links to cold, dry climates. As humans drifted away from the equator longer, thinner noses allowed for better conditioning of the arid air found at higher latitudes.

A recent study conducted by researchers from Pennsylvania State University seems to confirm Thomson’s theory. Using 3D facial imaging, they examined a variety of nose measurements in people of East Asian, Northern European, South Asian, and West African descent. The researchers found a strong correlation between nostril width and local climate conditions suggesting that climate, at least partially, triggered nose shape and size evolution.

Into the Fold

Eyes come in all shapes, sizes, and colors. Still, almond has emerged as the most ideal eye shape and green as the most ideal color. Global beauty standards and the cosmetics industry have placed a superficial importance on eye shape. There are hundreds of YouTube videos and articles telling us which makeup looks are best suited for our eyes. Blepharoplasty, eyelid surgery, has become the third most common plastic surgery procedure in the world with 1.1 million operations taking place in 2018 alone. Blepharoplasty, better known as double eyelid surgery, has become especially popular in Asia where many people have an epicanthic fold, or monolid.

No matter how much make-up companies and beauty gurus want us to believe, eye shapes don’t actually vary much from person to person. Scientists still don’t have a definitive explanation for the appearance of an epicanthic fold in some populations. This facial feature results from greater levels of fat deposition under the skin around the eyes. This has led some to believe that it evolved as a response to the cold winds and bright light found in the arctic regions.  

As you can imagine, strong UV exposure is not only damaging to the skin but can also have a harmful effect on our eyes. Light rays, like those emitted from the sun, are more intensely reflected off white surfaces such as the snow found in the arctic. The presence of an epicanthic fold acts like a shield protecting the eye from this bright light. Asiatic people originated from Mongolia where they had to contend with this obstacle in addition to strong, frigid winds. Just like fat keeps some animals warm in the winter, the extra adipose tissue around the eye acts as an insulator protecting it from the cold air.

Play Nice in the Sandbox

We all have a great appreciation for the variety found in nature: the assortment of flowers in a bouquet, the countless number of fruits and vegetables at the grocery store, the many breeds of cats and dogs. We just aren’t as readily tolerant of diversity in humans. We vilify people for being ‘different’, even when they can’t help it. Humans were always destined to be diverse. A 2014 study conducted by scientists from the University of California, Berkeley, found that human faces evolved to be unique and easily recognizable. A trait not found in any other species on the planet.

In an essay titled “Self Reliance” (1841) Ralph Waldo Emerson writes, “there is a time in every man’s education when he arrives at the conviction that envy is ignorance; that imitation is suicide”. Societal pressures to change the traits that make us ‘different’ have been around long enough. It is time for people to embrace these features because they were put there for a reason. All of our faces tell a unique story: not just our own, but the ones of the many people who came before us.