TIME Biology

Here’s Why You Have a Chin

Gorgeous—and pretty much useless
Chev Wilkinson; Getty Images Gorgeous—and pretty much useless

Hint: You could do perfectly well without it

Nature is nothing if not parsimonious, especially when it comes to the human body. There’s a reason we don’t have webbed feet or nut-cracking beaks like other species, and that’s because we don’t need them. The system isn’t perfect, of course. If you ever wind up having painful abdominal surgery, odds are pretty fair that it will be your good-for-nothing appendix that’s to blame. And wisdom teeth seem a lot less wise when you consider how often they fall down on the job and need to get yanked.

As it turns out, the same why-bother pointlessness is true of what you might consider one of your loveliest features: your chin.

Researchers have long wondered what the adaptive purpose of the chin could possibly be. Sexual selection seems like an obvious answer, since an attractive chin increases your chances of mating. But a feature needs a function before it can appear in the first place. Only then can it be assigned some aesthetic value.

The other, better answer is all about chewing. The jaw exerts enormous forces when it bites and chews—up to 70 lbs. per sq. in. (32 kg per 6.5 sq. cm) for the molars. Conscious clenching increases the figure, and people who grind their teeth in their sleep may exceed the average force 10-fold. What’s more, the jaw moves in more than just one axis, both chewing up and down and grinding side to side.

That, so the thinking went, might increase bone mass in the same way physical exercise builds muscle mass. And bone mass, in turn, may produce the chin. The problem with the theory, however, is that it doesn’t account for Neanderthals and other primates—including the great apes—which lack prominent chins but in many cases have far more powerful bites than we do.

To answer the riddle, Nathan Holton, a post-doctoral researcher who specializes in craniofacial structure in the University of Iowa school of orthodontics, selected 37 of the many subjects whose facial measurements have been taken regularly from age 3 to young adulthood, as past of the longstanding Iowa Facial Growth Study (yes, there is such a thing).

With the help of basic physics, it’s possible to determine how much force any one jaw exerts without the subjects’ ever having to be tested directly with a bite gauge. Measuring the geometry of what orthodontic researchers call the mandibular symphysis and what everyone else just calls the chin region, and comparing that to what is known as the bending moment arm—or the distance between where a force is initially applied (in this case the muscles in the jaw) and where that force is eventually felt (the chin)—yields a pretty good measure of force exerted.

“Think about removing the lug nuts from a wheel on your car,” Holton wrote in an e-mail to TIME. “The longer the wrench, the easier it is because the longer wrench increases the moment arm, allowing you to create more force.”

And more force, in this case, should mean more bone mass in the chin—but that’s not what the results of the new research showed. Not only did the two turn out to be unrelated in the 37 subjects studied, but Holton and his colleagues even found that as the face matures, the chin is less adept at resisting mechanical forces, which is the whole reason it was assumed to grow more pronounced in the first place.

So why did we grow chins at all? The answer is, we didn’t. Holton and his collaborator, University of Iowa anthropologist Robert Franciscus, instead suspect that the face shrank away from behind the chin as primitive and pre-humans became modern humans, making it appear larger relative to everything else. The reason, as with so many things in the human species, has to do with male behavior—specifically violent male behavior.

As humans migrated from Africa 20,000 years ago and settled down into societies, males had to become less competitive and more cooperative—giving an advantage to those with lower testosterone levels. And reduced testosterone softens and shrinks the craniofacial structure.

“What we are arguing is that modern humans had an advantage at some point to have a well-connected social network,” Franciscus said in a statement accompanying the study. “And for that to happen, males had to tolerate each other. There had to be more curiosity and inquisitiveness than aggression, and the evidence of that lies in facial architecture.”

It wasn’t until we had our chins that we set about assigning value to them—strong ones, weak ones, angular, round, cleft or dimpled, depending on your tastes. Those tastes—and the mating choices that arise from them—ensure that the chin will stay. It might be biomechanically useless, but you’d look awfully silly without one.

Read next: Can Plastic Surgery Make You More Likeable? A Close Look at a New Study

Listen to the most important stories of the day.

TIME anthropology

The Lost Hobbits of the Eastern Arctic

Wooden dolls were used both in ceremonies and as children's toys by the lost Paleo-Eskimos
University of Aberdeen/Qantiruuq, Inc Wooden dolls were used both in ceremonies and as children's toys by the lost Paleo-Eskimos

Scientists never understood what became of the Paleo-Eskimos who once peopled the north. Now they know—and there's new reason to miss them

Every indigenous group European explorers found when they first reached the Americas, from the Aztecs to the Inca to the Maya to the obscure Taino people were descended from a hardy bunch of immigrants who trekked over from Siberia more than 12,000 years ago, then spread east and south from there.

But when the Vikings began visiting Greenland and Baffin Island they bumped up against an indigenous group with a very different heritage—the Arctic dwelling people formerly known as Eskimos and now mostly called the Inuit. Based on archaeological evidence, scientists had established that they first came over from Siberia about 6,000 years ago and spread eastward across the very northernmost reaches of Canada, on the margins of the Arctic Ocean.

Then about 700 years ago, these so-called Paleo-Eskimos, gave way to a newer group known as the Thule culture. They displaced the earlier arrivals, just as our own invading ancestors had displaced the Neanderthals in Europe some 40,000 years earlier. What wasn’t clear, however, was whether the Paleo-Eskimos (or the Dorset, the name given to the last stage of Paleo-Eskimo cultural evolution) were simply absorbed into this new, more modern culture or whether, they vanished from the Earth, as the Neanderthals did.

But now it is, thanks to new paper in Science. Based on genetic analysis of 169 ancient human remains from Siberia, Alaska, Canada and Greenland, along with genome analyses of modern indigenous people, the authors can say definitively that the Paleo-Eskimos did indeed vanish; that the Inuit people who live in the North American Arctic today are the direct descendants of the Thule invaders; and that neither group is related to the Native American tribes that came to inhabit the rest of the Americas.

Exactly how the Dorset people were overwhelmed is unclear. Unlike the Neanderthals, they evidently didn’t mate with the invaders. “In other places,” said co-author Eske Willerslev of the Center for GeoGenetics at the University of Copenhagen’s National Museum of Natural History, at a press briefing, “we see people meeting, maybe fighting, but also having sex with each other.”

But the Paleo-Eskimos were genetically distinct. “There is some genetic admixture with the Thule,” said lead author Maanasa Raghavan, also at the Center for GeoGenetics “but it happened thousands of years earlier, most likely in the Old World.”

Instead, argued co-author William Fitzhugh, of the Smithsonian’s National Museum of Natural History, in Washington, “they were probably just overwhelmed.” The Thule, he explained, had bows and arrows, dogsleds and large whaling crews he calls “almost military” in their organization. The Dorset, by contrast, had much simpler tools, and lived in small, isolated villages.

“Socially and technologically,” he said, “they were no match for this Thule machine that spread across their territory in less than 100 years.” They were either pushed out into fringes where couldn’t survive, or they were annihilated, he said.

Until that happened, however, the Paleo-Eskimos were an astonishing success story, given that they endured in the harshest of climates, without major disruption for a staggering 5,000 years. It’s extraordinary, said Fitzhugh, that they maintained genomic and cultural continuity over such a long period, while other world cultures were going through radical changes.

“One might almost say,” said Fitzhugh,”that they were the Hobbits of the eastern Arctic—a strange, isolated, conservative people whose history we’re just starting to get to know.”

TIME Culture

Study: Society Flourished When Humans Got Less Manly

128583565
Getty Images A model of Peking man (Homo erectus pekinensis), who lived 1-2 million years ago

Does lower T lead to higher tech? Research links decrease in manly traits to an increase in sophisticated toolmaking in early humans

Some anthropologists now believe that advanced human behaviors like toolmaking only developed when early humans evolved to have lower levels of testosterone than their ancestors, according to a new study published in Current Anthropology.

“All of a sudden, in the archeological record, culture and advanced technology suddenly becomes more widespread. And at that time we also see a decrease in testosterone,” said the study’s lead author Bob Cieri, a graduate student at the University of Utah. “Before 50,00 years ago, there were brief flashes of advanced behavior and artifacts, but they’re not persistent and widespread.”

Cieri measured the browridge of different human skulls, which indicates the level of testosterone in the skeleton. Heavier brows and longer faces indicate more testosterone, and more rounded heads indicate less testosterone, according to Stephen Churchill, the Duke professor who supervised Cieri’s work. Cieri measured 13 human skulls that were more than 80,000 years old; 41 skulls between 10,000 and 38,000 years old; and over 1,200 20th-century skulls from different ethnic populations. He found that the modern skulls had substantially more rounded features and less heavy brows than the early skulls, indicating a drop in testosterone between our early ancestors and modern humans.

Cieri says the decrease in testosterone levels could be attributed to the rise in the Homo sapiens population, which meant that people had to be nicer to each other because they were living in closer quarters. “If population density starts increasing, not only are there more people in your immediate environment that you have to get along with, but all land would be occupied with human groups,” he explains. “You wouldn’t just go across to the other side of the valley to hunt bison by yourself, you’d go to the other side of the valley and maybe make a treaty with the other people who live there.”

It’s important to note that these early humans didn’t yet have “culture” as we know it — they were still hunter-gatherers, Cieri says, but they were much less aggressive about it. But he thinks this lowering of testosterone led to more cooperation between people, which laid crucial groundwork for cultural advances thousands of years later.

So if you’re still worried about low T after reading TIME’s recent cover story, “Manopause?!,” consider that a little less T isn’t always a bad thing.

TIME Archaeology

The Bodies in the Bogs: An Eerie Gift From the Iron Age

Tollund man, victim of human sacrifice by ritual strangulation in Denmark.
Werner Forman—UIG/Getty Images Tollund man, victim of human sacrifice by ritual strangulation in Denmark.

There are cold cases and there are cold cases, but it’s hard to beat the one that came to light on May 6, 1950, in Silkeborg, Denmark. The local folks were already on edge after reports that a schoolboy from Copenhagen had recently gone missing, and when two brothers from the nearby town of Tollund went digging for peat in a Silkeborg bog, they made a gruesome discovery: a buried body with a rope around its neck showing no signs of decomposition. This was a murder — and it was clearly a fresh one.

Except it wasn’t. The body wore no clothes other than a pointed, leatherized, sheepskin cap that seemed not of this era. The rope was handwoven, not machine-made. And the face of the victim was covered with stubble — clearly not belonging to a young boy. All that, plus the noose, plus the ancient history of the site, suggested that this was not a body from the early years of the space age, but the latter years of the Iron Age. Carbon dating confirmed that — placing the man’s death somewhere between 375 B.C. and 210 B.C.

The extraordinarily well-preserved state of what became known as the Tollund Man was due to the unique chemistry of the bog, with its lack of oxygen, cool temperatures and bacteria-unfriendly acidic environment. The fact that there were remains to unearth at all suggested that, despite the noose, this man was not technically murdered or hanged as a criminal. If he had been, he would have been cremated. Rather, he was probably ritually hanged as a spiritual sacrifice.

Some parts of the man’s body did not fare as well as others. His arms and hands were reduced to little more than a thin layer of toughened tissue covering bones. But his internal organs — particularly heart, lungs and liver — were very well preserved. He is thought to have been about 40 when he died and stood no taller than about 5 ft. 3 in. (1.6 m).

The Tollund Man is by no means the only bog person to have been uncovered in recent decades. About a thousand others have been found in Ireland, England, Denmark and the Low Countries. This July 27, which is, yes, International Bog Day, is a good time to tip a hat to these unglamorous mires of mud and decayed vegetation. They provide an extraordinary look into an often mysterious past — and allow the people of the Iron Age to make themselves mutely known in the modern one.

TIME Out There

Women Unveiled: Marc Garanger’s Contested Portraits of 1960s Algeria

Marc Garanger’s portraits of Algerian women in 1960s regroupment villages are strong reminders of the power of the photograph as historical record.

For France, the trauma of the Algerian War (1954-1962) was not unlike the experience of the Vietnam War for the United States. But, unlike the conflict in Vietnam, few photographic documents exist from that period in Algeria: it is as if the French responded with collective amnesia. Marc Garanger’s Algerian Women is one of the few photographic essays dedicated to that painful period.

In 1960, Garanger, a 25-year-old draftee who had already been photographing professionally for ten years, landed in Kabylia, in the small village of Ain Terzine, about seventy-five miles south of Algiers. Like many politically engaged young men, he had put off his departure for the army as long as possible, hoping that the war would end without him. He was soon selected as his regiment’s photographer.

General Maurice Challes, head of the French army, attacked the mountain villages occupied by two million people, some of whom had joined the Algerian resistance, the FLN. To deprive the rebels of their contacts with the villagers, he decided to destroy the villages and transfer the population into regroupment villages, a euphemism for concentration camps. Soon Garanger’s commanding officer decreed that the villagers must have identity cards: “Naturally he asked the military photographer to make these cards,” Garanger recalls. “Either I refused and went to prison, or I accepted. I understood my luck: it was to be a witness, to make pictures of what I saw that mirrored my opposition to the war. I saw that I could use what I was forced to do, and have the pictures tell the opposite of what the authorities wanted them to tell.”

The women that Garanger portrayed came from neighboring villages. Either Berber or Muslim, they had never before come into contact with Europeans. When Garanger arrived, there was a detachment of armed men with machine guns across their shoulders, an interpreter, and the commander. The women would be lined up, then each in turn would sit on a stool outdoors, in front of the whitewashed wall of a house. Without their veils, their disheveled hair and their protective tattoos were exposed. Their lined faces reflected the harshness of their life. The stiffness of their pose and the intensity of their gaze evoke early daguerreotypes.

“I would come within three feet of them,” Garanger remembers. “They would be unveiled. In a period of ten days, I made two thousand portraits, two hundred a day. The women had no choice in the matter. Their only way of protesting was through their look.”

“It is this immediate look that matters,” Garanger continues. “When one discharges a condenser, a spark comes out: to me, photography involves seizing just that instant of discharge. In these sessions, I felt a completely crazy emotion. It was an overwhelming experience, with lightning in each image. I held up for the world a mirror, which reflected this lightning look that the women cast at me.”

In the Middle East, the veil is like a second skin among traditional people. It may be taken off only within the secrecy of the walls, among women or between husband and wife, but never publicly. Garanger’s portraits symbolize the collision of two civilizations, Islamic and Western, and serve as an apt metaphor for colonization. The women’s defiant look may be thought of as an ‘evil eye’ that they cast to protect themselves and curse their enemies.

Fifty years after Algeria’s independence was proclaimed, Garanger’s contested portraits have not lost their strength. When he went back to Algeria in 2004 to meet those he had photographed, he found that the pictures he had taken were often the only ones that the women ever had of themselves, and they welcomed his return: he had become the keeper of their memory. This month, his portraits will be exhibited in Algiers.


Garanger’s portraits are currently being exhibited at the Musée d’Art Moderne, Algiers (April 20 – August 30).

Carole Naggar is a photo historian and poet. She recently wrote for LightBox on Chim’s images of children in Europe after World War II and the visual fables of Pentti Sammallahti.


Your browser is out of date. Please update your browser at http://update.microsoft.com