The Evolution of Facial Diversity: Why do we Look so Different From One Another?

Have you ever looked at a group of animals of the same species and wondered why they appeared so similar? While humans have distinct features, allowing us to identify specific people, it is difficult for us to tell most members of an animal species apart. Unlike us, their faces usually appear so similar that they can't be distinguished. So why do human faces look so different from each other? 

Facial features among different people vary in length, placement, size, and more

First of all, the main reason we don't all appear the same is because of genetic variation. Through the processes of recombination and independent assortment, the combinations of genes you get from your parents will usually look completely different from that of your siblings. So everybody's genes are unique. That being said, it's important to note that humans aren't nearly as genetically diverse as most other species. If your DNA were compared with another random human's, there would only be around 1 difference per 1,000 base pairs. Animals also use the same processes during meiosis to create genetic variation, yet within the same species they look nearly identical. So if we're so genetically similar to each other, why do we all look so different? There is a new hypothesis:

The evolution of facial uniqueness may have arisen through a type of selection called intersexual selection. This type of selection occurs when an individual of a species has an advantage in finding a mate because their characteristics are more desirable, like a male peacock's colorful feathers attracting females. A more unique facial trait may have been found more attractive, leading to offspring with more distinctive facial features. The reason that other animals didn't evolve the same amount of facial variation as humans is because they don't need to rely on their vision nearly as much as people do. For humans, vision is an incredibly important part of our lives. One study shows that we might perceive up to 80% of our stimuli just from our sight. Meanwhile, animals typically make much more use of their other senses. Some species like dogs and cats evolved to have a particularly strong sense of smell, so they can use that to recognize each other. Birds can recognize each other through their calls. Dolphins can recognize each other through a combination of hearing and taste. When compared with other animals, human senses are generally weaker. So with humans' dependence on their vision, it makes sense that we would evolve in a way that compliments our needs. Humans need to look different from one another because we wouldn't be able to tell each other apart through any sense other than vision.

Bats evolved as nocturnal organisms and typically reside in dark areas. They are able to distinguish each other's voices through echolocation rather than vision, so they don't need to look different from one another.

Genes that code for facial features often have much more variation than genes encoding for other parts of the body. Researchers investigating these genes found that they are much less likely to be linked to each other than genes not encoding for facial features. This means that something like nose shape wouldn't influence eye shape, while, on the other hand, many other traits of the body are encoded by genes that are inherited together. This allows there to be much more diversity in the combination of facial traits that each human acquires. There are also far more genes encoding for facial features than features of any other part of the body. Thousands of genes are actively involved in sculpting your face. The image below shows the results of a study examining how different genes affect different facial features:

More than 130 regions in your DNA encode for you face's traits

This study revealed many interesting findings that show how important facial genes are. Although genes encoding for different parts of the face are usually not linked to each other, they can help influence other parts of the body. Facial features are important indicators of health. Parents can sometimes identify genetic disorders in their children early on because of distinctive facial features. Most interestingly, there appears to be a link between certain facial features and cancer, which implies that some of the genes coding for parts of your face also hold some sway over the likelihood that you will develop this disease. 

Although there are many different options for how facial diversity arose, it is nevertheless an important part of human life that has provided us with many advantages compared to other species. Many animals have to also rely on other senses to identify other members of their species, while us humans are able to recognize each other based on facial features alone. This adaptation is incredibly important to humans, especially recently, with new creations such as facial recognition software, which helps us to identify criminals, missing people, or can just be used for our convenience. Facial diversity allows us to recognize acquaintances and makes each person appear as a completely distinct individual. Whether or not a person likes their appearance, having an exclusive set of features is undeniably an important aspect of each of our unique identities.