Face value

Why do we look different? This is a question that has no easy answers. Everyone has eyes, nose, ears and a mouth, yet every face is different. No two faces are truly alike, except for those of identical twins. And there are instances when we can tell the country or region of a person by looking at his facial features.

There is no doubt that this is an evolutionary feature and it is indeed not limited to humans. If you have two dogs (or cats) at home, they will look different from one another. But why this diversity? That diversity may have evolved to make it easier to recognise other people, according to latest research.

“An individual may actually benefit from having a unique face,” says lead investigator Michael Sheehan, a postdoctoral fellow at the University of California, Berkeley. “It's like evolving a name tag.” The individuality of faces may stem from our need to recognise one another, an important challenge for social species.

For this study, Sheehan and his colleagues analysed a U.S. Army database that includes dozens of face and body measurements for thousands of its service members, from the distance between pupils to the length of the calf.

The shape and configuration of a human face are much more variable, compared with other body parts, the study found. Furthermore, genes that have been linked to the face structure vary more than DNA in other regions of the body. This suggests that the forces of evolution have selected for facial diversity, perhaps to make individuals more recognisable to other people, the researchers say. We also know that some parts of the face, especially the eyes, enhance the process of identification.

Hence, the blocking of eyes in certain photographs in newspapers and magazines. One unique face and one name can and do end any confusion that may arise in others’ minds.

Confused

There are many situations in which it might be evolutionarily costly to be confused with another person, Sheehan says, such as if an enraged neighbour mistakes you for their enemy.

This type of situation would have been common in man’s early hunter-gatherer periods, when it was vital to guard whatever you hunted and any domestic animals. If you cannot identify your enemy and your friend/family member, the consequences can be disastrous. Faces may have served as a primitive form of Identification Friend or Foe (IFF)signalling.

However, if facial diversity is an evolved trait, it may have arisen for many reasons other than recognition, researchers have noted.

Even within closely related groups of people and animals, facial features are quite variable on the genetic level, the new study shows. That seemed to be true for the paper wasp. Animals can not only identify their “friends” but also individual humans, even after a lapse of several years.

The saying that “elephants never forget” is absolutely true in this sense, but many lesser animals have been known to identify humans who have been closely associated with them after a lapse of five or more years. Again, it is the uniqueness of the faces that helps them to make that distinction.

This alone indicates that evolution played a role in facial diversity. For this study, the researchers looked at the genomic sequences of 836 people of European, African, or Asian descent from the 1000 Genomes Project, a freely available catalog of genetic information. The researchers focused on 59 stretches of DNA previously linked to facial features.

These DNA codes were more variable than the rest of the genome was, and were more variable than regions associated with a person's height, the study found. To get a sense of when this diversity cropped up during human evolution, the researchers also compared the DNA of modern humans to that of a Neanderthal individual and of a Denisovan, another early human relative.

In both the modern and ancient DNA, two genes - one related to the distance between the chin and bridge of the nose, and the other to nose shape - had similar levels of variability, suggesting that facial diversity evolved before modern humans did.

That high level of genetic variability probably means that evolutionary forces are at play in shaping the diversity of faces.

In fact, there was a recent study which concluded that 20,000 years from now, the human face as a whole could be a little different. Humans will change over time and if they begin space travel they will have to adapt to those conditions as well, which will further challenge evolutionary forces.

Beauty

Humans, of course, see many other variables in a face. The concept of beauty is uniquely human. As the saying goes, “beauty is in the eye of the beholder”. A face that one person may think of as “beautiful” may not have the same appeal to someone else. Likewise, if you think someone is ugly, another person might have a different opinion. Many people also look for the colour of a person’s face. Most Sri Lankans are keen to get fairer skin, whereas many in so-called “white” countries want to get a tan or darker skin.

These are very much individual preferences, but some of them are ingrained at society level. And we all like to look young, especially in the face, regardless of our age. Cosmetic and drugs manufacturers as well as scientists who have no connection to or interest in the beauty industry are working overtime to find an elixir of sorts which will enable us to turn back the clock and literally look forever young.

Indeed, we are yet to learn fully why we age and why our faces become somewhat different.

The eyes are perhaps the only facial feature which does not change physically (in terms of size) even though they can also become weak. Perhaps the process of evolution itself will give us an answer to this timeless question.