Why is your face unique? New study offers clues.

You can thank evolution for your one-of-a-kind mug, according to research that finds that chance alone cannot account for each person's distinctive facial features. 

Melanie Stetson Freeman/The Christian Science Monitor
NEW YORK, NY - MAY 16: New York University (NYU) holds its 180th commencement ceremony in Yankee Stadium in New York, New York, on May 16, 2012. Some 8,000 students receive undergraduate, graduate and professional degrees with about 25,000 family and friends watching from the stands. Photo by

Why is each human face unique? It's a question a child might ask.

The tempting response for a harried parent is, "Just because." After all, no two products of nature, be they clouds, snowflakes, or fingerprints, are exact duplicates. Mother Nature is no Henry Ford; those variations in shape, color, and texture are just part of the production process.

This response sounds reasonable, but new research suggests that things might not be so simple.

In a study published this past week in the scientific journal Nature Communications, Berkeley biologists Michael J. Sheehan and Michael Nachtman found that the differences in our facial traits, such as the shape of our noses and the distance between our eyes, are just too big to explained purely by chance

Instead, the authors hypothesize, there are evolutionary forces actively molding each of our faces so that they stand out from the crowd. Your face, they say, is what biologists call a signal, a mechanism that, like the shimmering tail of a peacock or the Day-Glo skin of a poison frog, sends a message to other organisms about who you are.

But how could one possibly test this hypothesis? Dr. Sheehan reasoned that if our unique facial traits are indeed a signal, then there should be greater variation among human faces than among other human body parts.

And that's exactly what Sheehan and Dr. Nachtman found when they examined data from the US Army Anthropometric Survey. Conducted in 1988 with the aim of improving the design of military clothing and equipment, ANSUR, as the study is known, gathered detailed body measurements of thousands of soldiers, including the distance of the tip of the nose to the back of the head, the circumference of the elbows, and the width of the feet.

The ANSUR data showed that facial traits, such as the distance between the eyes and the height of the ears are, on average, more variable than other body traits such as the length of the forearm and the height of the waist. What's more, facial traits tend to be independent of other facial traits while other body measurements tend to correlate. Put another way, people with long arms tend to have long legs, but people with, say, widely spaced eyes are not particularly prone to having wide noses.

A look at the DNA tells the same story. Using data collected by the 1000 Genomes project, a comprehensive database on human genetic variation, the researchers found that parts of the human genome thought to determine the shape of the face displayed more variability than regions that determine other morphological traits.

"All three predictions were met: facial traits are more variable and less correlated than other traits, and the genes that underlie them show higher levels of variation," Nachman said in a news release. "Lots of regions of the genome contribute to facial features, so you would expect the genetic variation to be subtle, and it is. But it is consistent and statistically significant."

"I was surprised that it worked," Sheehan, a postdoctoral researcher at UC Berkeley’s Museum of Vertebrate Zoology, told the Monitor. "The more complex a trait is, the harder it is to find patterns." 

The pair also compared these genomes with those of two types of ancient humans – Neanderthals and Denisovans. They found similar variation in regions associated with facial traits, suggesting that this kind of facial uniqueness dates at least as far back as our common ancestor. 

Sheehan previously studied paper wasps, animals that, like humans, have evolved highly variable faces for themselves. He believes that, for certain social species, being uniquely identifiable has its evolutionary advantages when it comes to mating, aggression, and parental care. 

"Other species that have a lot more fluid social structures," says Sheehan. "Identity is not as important to them."  But in humans "even a very small cost of confusion is enough to generate a lot of diversity."

Sheehan and Nachtman say that our one-of-a-kind faces suggest that human social complexity, often credited as helping give rise to intricate processes inside our skulls involving language, attention, memory, and reasoning, also leaves prominent marks on the outside.

"It's not just our intelligence and cognitive abilities that have evolved," says Sheehan. "Being in complex social systems has continued to shape our morphology."

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to Why is your face unique? New study offers clues.
Read this article in
QR Code to Subscription page
Start your subscription today