Peter Ungar: It’s not that your teeth are too big: your jaw is too small

We hold in our mouths the legacy of our evolution. We rarely consider just how amazing our teeth are. They break food without themselves being broken, up to millions of times over the course of a lifetime; and they do it built from the very same raw materials as the foods they are breaking. Nature is truly an inspired engineer.

But our teeth are, at the same time, really messed up. Think about it. Do you have impacted wisdom teeth? Are your lower front teeth crooked or out of line? Do your uppers jut out over your lowers? Nearly all of us have to say ‘yes’ to at least one of these questions, unless we’ve had dental work. It’s as if our teeth are too big to fit properly in our jaws, and there isn’t enough room in the back or front for them all. It just doesn’t make sense that such an otherwise well-designed system would be so ill-fitting.

Other animals tend to have perfectly aligned teeth. Our distant hominin ancestors did too; and so do the few remaining peoples today who live a traditional hunting and gathering lifestyle. I am a dental anthropologist at the University of Arkansas, and I work with the Hadza foragers of Africa’s great rift valley in Tanzania. The first thing you notice when you look into a Hadza mouth is that they’ve got a lot of teeth. Most have 20 back teeth, whereas the rest of us tend to have 16 erupted and working. Hadza also typically have a tip-to-tip bite between the upper and lower front teeth; and the edges of their lowers align to form a perfect, flawless arch. In other words, the sizes of Hadza teeth and jaws match perfectly. The same goes for our fossil forebears and for our nearest living relatives, the monkeys and apes.

So why don’t our teeth fit properly in the jaw? The short answer is not that our teeth are too large, but that our jaws are too small to fit them in. Let me explain. Human teeth are covered with a hard cap of enamel that forms from the inside out. The cells that make the cap move outward toward the eventual surface as the tooth forms, leaving a trail of enamel behind. If you’ve ever wondered why your teeth can’t grow or repair themselves when they break or develop cavities, it’s because the cells that make enamel die and are shed when a tooth erupts. So the sizes and shapes of our teeth are genetically pre-programmed. They cannot change in response to conditions in the mouth.

But the jaw is a different story. Its size depends both on genetics and environment; and it grows longer with heavy use, particularly during childhood, because of the way bone responds to stress. The evolutionary biologist Daniel Lieberman at Harvard University conducted an elegant study in 2004 on hyraxes fed soft, cooked foods and tough, raw foods. Higher chewing strains resulted in more growth in the bone that anchors the teeth. He showed that the ultimate length of a jaw depends on the stress put on it during chewing.

Selection for jaw length is based on the growth expected, given a hard or tough diet. In this way, diet determines how well jaw length matches tooth size. It is a fine balancing act, and our species has had 200,000 years to get it right. The problem for us is that, for most of that time, our ancestors didn’t feed their children the kind of mush we feed ours today. Our teeth don’t fit because they evolved instead to match the longer jaw that would develop in a more challenging strain environment. Ours are too short because we don’t give them the workout nature expects us to.

There’s plenty of evidence for this. The dental anthropologist Robert Corruccini at Southern Illinois University has seen the effects by comparing urban dwellers and rural peoples in and around the city of Chandigarh in north India – soft breads and mashed lentils on the one hand, coarse millet and tough vegetables on the other. He has also seen it from one generation to the next in the Pima peoples of Arizona, following the opening of a commercial food-processing facility on the reservation. Diet makes a huge difference. I remember asking my wife not to cut our daughters’ meat into such small pieces when they were young. ‘Let them chew,’ I begged. She replied that she’d rather pay for braces than have them choke. I lost that argument.

Crowded, crooked, misaligned and impacted teeth are huge problems that have clear aesthetic consequences, but can also affect chewing and lead to decay. Half us could benefit from orthodontic treatment. Those treatments often involve pulling out or carving down teeth to match tooth row with jaw length. But does this approach really make sense from an evolutionary perspective? Some clinicians think not. And one of my colleagues at Arkansas, the bioarchaeologist Jerry Rose, has joined forces with the local orthodontist Richard Roblee with this very question in mind. Their recommendation? That clinicians should focus more on growing jaws, especially for children. For adults, surgical options for stimulating bone growth are gaining momentum, too, and can lead to shorter treatment times.

As a final thought, tooth crowding isn’t the only problem that comes from a shorter jaw. Sleep apnea is another. A smaller mouth means less space for the tongue, so it can fall back more easily into the throat during sleep, potentially blocking the airway. It should come as no surprise that appliances and even surgery to pull the jaw forward are gaining traction in treating obstructive sleep apnea.

For better and for worse, we hold in our mouths the legacy of our evolution. We might be stuck with an oral environment that our ancestors never had to contend with, but recognising this can help us deal with it in better ways. Think about that the next time you smile and look in a mirror.

Evolution’s Bite: A Story of Teeth, Diet, and Human Origins by Peter Ungar is out now through Princeton University Press.Aeon counter – do not remove

UngarPeter S. Ungar is Distinguished Professor and director of the Environmental Dynamics Program at the University of Arkansas. He is the author of Evolution’s Bite: A Story of Teeth, Diet, and Human Origins, Teeth: A Very Short Introduction and Mammal Teeth: Origin, Evolution, and Diversity and the editor of Evolution of the Human Diet: The Known, the Unknown, and the Unknowable. He lives in Fayetteville, Arkansas.

This article was originally published at Aeon and has been republished under Creative Commons.

Craig Bauer: The Ongoing Mystery of Unsolved Ciphers (and new hope)

When a civilization first develops writing and few people are literate, simply putting a message down on paper can be all that is required to keep an enemy from understanding it. As literacy spreads, a more sophisticated method is needed, which is why codes and ciphers, a.k.a. “secret writing,” always follow closely on the heels of the discovery of writing. Over the millennia, ciphers have become extremely sophisticated, but so too have the techniques used by those attempting to break them.

In recent decades, everyone from mathematicians and computer scientists to artists and authors have created ciphers as challenges to specialists or the general public, to see if anyone is clever enough to unravel the secrets. Some, like the first three parts of James Sanborn’s sculpture Kryptos and the ciphers appearing in the television show Gravity Falls, have been solved, while others remain mysteries. The highly secretive online society known as Cicada 3301 has repeatedly issued such challenges as a means of talent scouting, though for what purpose such talented individuals are sought remains unknown. One unsolved cipher was laid down as a challenge by former British army intelligence officer Alexander d’Agapeyeff in his book Codes & Ciphers (1939). Sadly, when frustrated letters of enquiry reached the author, he admitted that he had forgotten how to solve it! Another was made by the famous composer Edward Elgar in 1897 as a riddle for a young lady friend of his. She, along with various experts, all failed to ferret out the meaning and Elgar himself refused to reveal it.

 

Elgar's cipher

Elgar’s cipher

 

Many unsolved ciphers appear in much more serious contexts. The serial killer who referred to himself as “The Zodiac” was responsible for at least five murders, as well as the creation of several ciphers sent to San Francisco newspapers. While the first of these ciphers was solved, others remain unbroken. Could a solution to one of these lead to an identification of the killer? Although many have speculated on his identity, it has never been firmly established. The Zodiac is not the only murderer to have left us such mysterious communiques, he is just the best known. Other killers’ secrets have persisted through relative obscurity. How many readers have heard of Henry Debsonys? In 1883, a jury sentenced him to death for the murder of his wife, after deliberating for only nine minutes. But this unfortunate woman was Henry’s third wife and the first two died under strange circumstances. Had Henry killed all of them? Will the ciphers he left behind confirm this? I think his ciphers will be among the first to fall this year, thanks to a major clue I provide in my book, Unsolved: The History and Mystery of the World’s Greatest Ciphers from Ancient Egypt to Online Secret Societies. There are many more such criminal ciphers. One deranged individual even sent threatening letters containing ciphers to John Walsh of America’s Most Wanted fame! The FBI’s codebreakers maintain a list of their top unsolved ciphers. At present, only two of these are known to the public, but many others that didn’t make the top 10 are available for anyone to try to crack.

How do codebreakers, whether amateur or professional, meet the challenges they face? Statistics and other areas of mathematics often help, as do computers, but two of the codebreakers’ most powerful tools are context and intuition. This is why ciphers have often been broken by amateurs with no programming skills and little knowledge of mathematics. Enter Donald Harden, a high school history teacher, who with assistance from his wife Bettye, broke one of the Zodiac killer’s ciphers by guessing that the egotistical killer’s message would begin with “I” and contain the word “KILL.” Context allows the attacker to guess words, sometimes entire phrases, that might appear in the message. These are known as cribs. During World War II, the German word eins (meaning one) appeared in so many Nazi messages that a process known as “einsing” was developed, searching the cipher for the appearance of this word in every possible position. In today’s ciphers, the word President appears frequently.

Of course, time and again cribs and intuition can lead in the wrong direction. Indeed, the single most important attribute for a codebreaker is patience. A good codebreaker will have the ability to work on a cipher for months, for that is sometimes what it takes to reach a solution, ignoring the body’s normal demands for food and sleep; during World War I, the French codebreaker Georges Painvin lost 33 pounds over three months while sitting at a desk breaking the German ADFGX and ADFGVX ciphers.

Fig 2

Fig 3Is it possible that some of the earliest known ciphers, dating from the ancient world, have survived unread by anyone other than those they were created for? I believe this is the case and that they’ve been hiding in plain sight, like the purloined letter in Poe’s classic tale. Those studying ancient cultures have long been aware of so-called “nonsense inscriptions.” These appear on Egyptian sarcophagi, Greek vases, runestones, and elsewhere. They are typically dismissed as the work of illiterates imitating writing, merely because the experts cannot read them. But all of these cultures are known to have made use of ciphers and some of the contexts of the inscriptions are so solemn (e.g. sarcophagi) that it’s hard to believe they could be meaningless. I’d like to see a closer examination of these important objects. I expect some of the messages will be read in the near future, if cryptologists can form collaborations with linguists. These two groups have worked together successfully in military contexts for many decades. It is time that they also join forces for historical studies.

With a very large number of unsolved ciphers, spanning millennia, having been composed by a diverse group of individuals, it seems likely that it will take a diverse group of attackers, with skills ranging over many disciplines, to solve them. Some mysterious texts may reveal themselves to clever computer programmers or linguists, others to those taking the psychological approach, getting into the creator’s head and guessing phrases he or she used in the cipher, and some may be broken by readers who manage to discover related material in government archives or private hands that provides just enough extra information to make the break. I look forward to seeing the results!

BauerCraig P. Bauer is professor of mathematics at York College of Pennsylvania. He is editor in chief of the journal Cryptologia, has served as a scholar in residence at the NSA’s Center for Cryptologic History, and is the author of Unsolved!: The History and Mystery of the World’s Greatest Ciphers from Ancient Egypt to Online Secret Societies. He lives in York, Pennsylvania.

Paul Strode: Teaching The Serengeti Rules

CarrollIn January of 2016 I was asked by Laura Bonetta at the Howard Hughes Medical Institute (HHMI) to write a teacher’s guide for the short film Some Animals Are More Equal than Others: Keystone Species and Trophic Cascades. At the same time, Molecular Biologist Sean B. Carroll, the HHMI Vice President of Science Education, was putting the finishing touches on his new book, The Serengeti Rules. To help expedite my research for writing the teacher’s guide for the short film, Laura sent me a pre-pub copy of the book and suggested I read Chapter Six: “Some Animals Are More Equal than Others.”

Instead of going straight to Chapter Six, I started reading from the beginning.

Before I was even halfway through the first chapter, I thought to myself, this book is going to change the way I teach. At the core of Carroll’s storytelling is the observation that everything is regulated, from molecules to megafauna. Indeed, for most of my career teaching biology I have kept my focus on Theodosius Dobzhansky’s argument that “nothing in biology makes sense except in the light of evolution.” But Carroll has now made it clear that nothing in biology also makes sense except in the light of regulation.

To make a long story short, I wrote the short film teachers guide with the help of Chapter Six in The Serengeti Rules and immediately followed that task by reviewing the book for The American Biology Teacher so that other teachers might benefit from reading the book. In my review, I argued that The Serengeti Rules “should be required reading for students in all fields of science, but especially those pursuing careers in biology education.” My review caught the attention of Carroll’s editor at Princeton University Press, Alison Kalett. Alison was curious to know if teachers like me that planned to use Carroll’s book to enhance their biology courses would find it useful if educational supplementary materials were made available… for free. Alison and I came up with a plan and I began to write.

The Serengeti Rules came out in March of 2016 and one of Carroll’s first public discussions about the book was at the annual Professional Development Conference of the National Association of Biology Teachers in Providence, Rhode Island. Several hundred teachers showed up to hear from Dr. Carroll and it was standing room only. As word got out that supplementary materials were being prepared for Carroll’s book, inquiries began to pop up on social media.

Carroll

The Educational Supplement was released in May and is a document that a teacher can use immediately in the classroom.

Carroll

The questions come in various styles and are designed to invoke classroom discussion, require students to synthesize and connect various biological concepts, get students to engage with ecological data from the published journal articles, and have students analyze and graph data that relate to what they are reading in The Serengeti Rules. For example, the question below relates to Chapter Four of The Serengeti Rules, “Fat, Feedback, and a Miracle Fungus.” The question can be used as a formative assessment question that marries real data with the nature of science and covers several components of the Advanced Placement and International Baccalaureate biology course content.

Carroll

Teachers have already begun planning to use The Serengeti Rules to enhance their courses and since the release of the supplement have expressed their gratitude that it is available and free!

Carroll

And of course, I have assigned The Serengeti Rules as summer reading for my 65 AP/IB biology students and I am looking forward to using the questions in the fall to incite discussion and enhance learning and understanding.

Thank you, Sean B. Carroll, for giving us The Serengeti Rules!

Amazons in all Shapes, Sizes, and Colors: What the Wonder Woman Movie Got Right

by Adrienne Mayor

Were Amazons—and their real-life counterparts in antiquity—really as diverse as they appear in Wonder Woman?

Wonder Woman opens with a breathtaking  panorama of Themiscyra, the fantasy island populated by powerful women, a paradise magically isolated in time and space from the modern world of men and their ruthless wars. This is where the little wonder girl Diana raised by a triumvirate of formidable females: Queen Hippolyta, General Antiope, and her aunt Melanippe.

In the film, Themiscyra is a self-contained, women-only society of indomitable warriors, devoted to using their deadly expertise to fight on the side of all that is fair and good. We see how idealistic young Diana is rigorously trained for hand-to-hand combat, learning rugged martial arts alongside the toughest, most courageous warrior women the world has ever known: Amazons of ancient Greek myth.

The beginning scenes show us daily life in Themiscyra, with the entire citizenry of warlike women engaged in military exercises. As far as the eye can see, vast fields are filled with female soldiers displaying their prowess in an amazing array of skills. Frame after frame, there are women wrestling, boxing, sword fighting; women performing gymnastic feats on galloping horses; women thrusting daggers and twirling battle-axes; keen-eyed archers on foot and on horseback; acrobatic ninjas and javelin throwers with deadly aim. And in the following scenes of the battle on the beach—pitting the Amazons against boatloads of nasty German soldiers—the dizzying kaleidoscope intensifies, drawing us into a maelstrom of whirling, grappling, leaping, kicking, punching, stabbing, spearing, soaring, kickass female fighters. A crucial element in the  scene’s powerful impact is the perfectly natural diversity of super-fit body types and skin colors.

The magnificence of the Amazons of Themiscyra would have been impossible to pull off with typical Hollywood actresses pretending to be fierce warrior women. It was the brilliant decision of director Patty Jenkins to cast real-life athletes and sports champions as Wonder Woman’s companions.

And that choice ensured that women of Themiscyra display a variety of skills, body sizes, shapes, ages, and skin colors. The diversity is stunning: the Amazons are tall and short, robust and lithe, young and mature, lean and muscle-bound, stolid and mercurial; pale and dark—and everything in between.

In ancient Greek myth, Amazons were warrior women who gloried in battle who dwelled in exotic lands around the Black Sea. Now, thanks to evidence from history, art, and archaeology, we now know that the Amazons were modeled on real nomadic peoples of ancient Scythia, a vast territory that stretched from the real Themiscyran plain on the Black Sea to Mongolia. These myriad tribes had their own languages and were ethnically diverse, but they shared a lifestyle centered on fast horses, bows and arrows, and constant warfare. Their egalitarian lifestyle meant that girls and boys learned to ride, shoot arrows, and fight and the women rode to war with the men.

The Scythians left no writings, but modern archaeology, ancient art, and historical descriptions by their neighbors, the Greeks and Chinese, tell us what they were like. Human remains from Scythian graves show both European and Asian traits, characteristics evident in steppe nomads’ descendants today. Females buried with weapons ranged in age from 10 to 45. Some 2,000 years ago, Greek and Roman historians reported that some Scythians had dark eyes and hair, while others were blond or red-headed with blue eyes. Notably, ancient Chinese chronicles confirm this ethnic diversity, describing some Scythians of Inner Asia as red-haired with green eyes.

Beginning in the sixth century BC, Greek artists painted thousands of images of Amazons on vases. The pictures took on more and more realistic details of actual Scythian nomads as they became more familiar with steppe peoples. Vase paintings show tall and petite Amazons, husky and slender Amazons, often together in the same scene. Most have dark hair but there are some blonde and red-haired Amazons. There were ancient Greek tales of Amazons of Africa and Ethiopians were allies of the Amazons in the legendary Trojan War. Vase paintings show African archers dressed like Amazons.

Wonder Woman‘s vision of all kinds of Amazon warriors making themselves physically strong—and then proving their valor in violent combat and emerging victorious—is unprecedented in cinematic history. The grandeur of the fighting scenes—the sheer physicality and diversity of the Amazons—arouses surging emotions of exhilaration in viewers, empowering for women and girls, a revelation for men and boys.

The fact that the multidimensional aspect of Wonder Woman‘s Amazon paradise is grounded in historical reality adds to the glorious authenticity of the film.

So breathtaking is the tribute to strong, real women in the first third of Wonder Woman that I’m joining the chorus of viewers requesting a prequel—we want more Amazons!

MayorAdrienne Mayor is a research scholar in classics and history of science at Stanford University, and the author of The Poison King: The Life and Legend of Mithradates, Rome’s Deadliest Enemy, a finalist for the National Book Award, and The Amazons: Lives and Legends of Warrior Women Across the Ancient World.

 

 

 

 

Image: © Marie-Lan Nguyen / Wikimedia Commons, via Wikimedia Commons

Face Value: Man or Woman?

In Face Value: The Irresistible Influence of First Impressions, Princeton professor of psychology Alexander Todorov delves into the science of first impressions. In honor of the book’s release, we’re sharing examples from his research every week.

Todorov

It is easy to identify the woman in the image on the right and the man in the image on the left. But the two images are almost identical with one subtle difference: the skin surface in the image on the left is a little bit darker. The eyes and lips of the faces are identical, but the rest of the image on the left was darkened, and the rest of the image on the right was lightened. This manipulation makes the face on the left look masculine and the face on the right look feminine. This is one way to induce the gender illusion. Here is another one.

Based on research reported in

  1. Russell (2009). “A sex difference in facial contrast and its exaggeration by cosmetics.” Perception 38, 1211–1219.

Todorov

Face Value: Eyebrows

In Face Value: The Irresistible Influence of First Impressions, Princeton professor of psychology Alexander Todorov delves into the science of first impressions. Throughout the month of May, we’ll be sharing examples of his research. 

 

Todorov

It is easier to recognize Richard Nixon when his eyes are removed than when his eyebrows are removed from the image. Our intuitions about what facial features are important are insufficient at best and misleading at worst.

 

Based on research reported in

  1. Sadr, I. Jarudi, and P. Sinha (2003). “The role of eyebrows in face recognition.” Perception 32, 285–293.

Todorov

Dominic Couzens: The extraordinary (and overlooked) water shrew

water shrewAsk most people whether they have heard of a water shrew and they’ll shake their head. If you tell them that there are 1.9 million water shrews in Britain and that they have a poisonous bite, then those same people are likely to raise their eyebrows, amazed they have never heard of it. The water shrew (not a water vole or a “water rat”) manages to keep a remarkably low profile for the extraordinary creature that it is.

Shrews are the mammals that look superficially like mice—they are small, brown and furry—yet are quite unrelated to them. They are flatter-bodied than mice and don’t hop, and have long snouts that move around in a somewhat robotic, mechanical fashion as they seek food. With small eyes (they are related to the almost-blind moles) and small ears, shrews lack the features that give mice and voles an easy identity to humankind. Shrews don’t live indoors or steal our food, either; they subsist on a diet of insects and other small living things. So shrews aren’t exactly on our doorsteps, asking to be noticed.

But shrews cross our paths alright, even if we aren’t looking. They are among the most abundant of all our mammals. Aside from the water shrew, there are 42 million common shrews and 8.6 million pygmy shrews in Britain; a veritable army of voracious insect- and worm-guzzlers living at our feet. They prefer to live in long grass, dense shrubbery, and other places where it’s easy to hide.

And, of course, they choose the waterside, too. The water shrew, the largest and best-turned out of our three common species, with its smart white underside contrasting with business-suit-black above, is the most aquatic of the three. Although it is perfectly at home in undergrowth away from water, its signature hunting method is to immerse in still or slow-flowing water, diving down to depths of 2m or more for up to 30 seconds, to snap up crustaceans, insect larvae, snails, worms, and small vertebrates such as newts, frogs, and fish. It is the only British mammal adapted to tap into this underwater niche of small freshwater life.

As it happens, the water shrew can also tackle prey larger than itself, by means of its remarkable venomous saliva, which immobilizes frogs or fish. The venom is a neurotoxin, causing paralysis and disorders of the blood and respiratory system. It is toxic enough to be a very unpleasant skin irritatant in humans that may take days to subside.

The water shrew has several adaptations to its preferred aquatic lifestyle. The surface of each foot is fringed with stiff hairs, increasing the area of the limb, like a flipper, allowing this mite to swim efficiently. The tail also has stiff hairs on the underside, making it act like a rudder, for steering. The hairs on the body also trap a layer of air, keeping the shrew warm underwater, even in the middle of winter.

Shrews, although small, don’t hibernate. Instead they must remain active throughout the winter, requiring a meal at least every two hours, day and night. It isn’t easy to sustain, and many shrews don’t survive. In fact, almost every adult dies after a single breeding season, meaning that only the juveniles born during the spring and summer survive to the next season—just another extraordinary aspect of this overlooked animal’s life.

Dominic Couzens is one of Britain’s best-known wildlife writers. His work appears in numerous magazines, including BBC Wildlife and BBC Countryfile, and his books include Secret Lives of Garden Wildlife and Britain’s Mammals: A Field Guide to the Mammals of Britain and Ireland.

Browse Our New History of Science & History of Knowledge 2017 Catalog

Our new History of Science and History of Knowledge catalog includes a fascinating account of the spread of Einstein’s theory of relativity, a timeless defense of the value of basic research, and a new history of archaeology from Eric Cline.

In The Road to Relativity, Hanoch Gutfreund and Jürgen Renn explored Einstein’s original paper, “The Foundation of General Relativity”. Gutfreund and Renn’s new book, The Formative Years of Relativity, follows the spread and reception of Einstein’s theory, focusing in particular on the Princeton lectures that formed the basis for his 1922 book, The Meaning of Relativity. Drawing on Einstein’s letters and contemporary documents, many of which are reproduced within, The Formative Years of Relativity provides invaluable context for perhaps the most important scientific breakthrough of the twentieth century.

The Formative Years of Relativity by Hanoch Gutfreund and Jurgen Renn

In 1939, Abraham Flexner, founding director of the Institute for Advanced Study, wrote an essay on The Usefulness of Useless Knowledge arguing that basic research into fundamental questions has always driven scientific innovation and warning against focusing too narrowly on immediately “useful” knowledge. In a time where pressure is constantly increasing on researchers to apply themselves to practical problems, we are pleased to bring Flexner’s enduring essay back into print, accompanied by a new essay from the current director of the Institute he founded, Robbert Dijkgraaf.

Use

We can think of no better person to present the history of archaeology than Eric H. Cline, author of 1177 B.C. Cline’s Three Stones Make a Wall gives a vivid account of the legendary excavations and the formidable personalities involved in archaeology’s development from amateur’s pastime to cutting edge science. As capable with a trowel as he is with a pen, Cline draws on his three decades of experience on digs to bring the how and the why of archaeology to the page alongside the history.

Cline Jacket

Find these and many more new titles in our History of Science & History of Knowledge 2017 catalog.

Face Value: Can you recognize the celebrities?

In Face Value: The Irresistible Influence of First Impressions, Princeton professor of psychology Alexander Todorov delves into the science of first impressions. Throughout the month of May, we’ll be sharing examples of his research. 

 

Todorov

 

A: Justin Bieber and Beyoncé

 

Todorov

Peter Ungar on Evolution’s Bite

UngarWe carry in our mouths the legacy of our evolution. Our teeth are like living fossils that can be studied and compared to those of our ancestors to teach us how we became human. In Evolution’s Bite, noted paleoanthropologist Peter Ungar brings together for the first time cutting-edge advances in understanding human evolution and climate change with new approaches to uncovering dietary clues from fossil teeth to present a remarkable investigation into the ways that teeth—their shape, chemistry, and wear—reveal how we came to be. Ungar recently took the time to answer some questions about his new book.

Why do paleontologists care so much about teeth? What makes them so special?

PSU: Paleontologists care about teeth because oftentimes, that’s all we’ve got of extinct species to work out details of life in the past. Teeth are essentially ‘ready-made fossils,’ about 96% mineral, so they survive the ages much better than other parts of the body. They are special because they come into direct contact with food, and can provide a bridge to understanding diet in the past. We can tease out the details by studying their size, shape, structure, wear, and chemistry. Teeth connect us to our ancestors, and them to their worlds. I like to think of nature as a giant buffet of sorts. I imagine animals bellying up to the sneeze guard on this biospheric buffet with empty plate in hand. Teeth can teach us about the choices they make; and it’s those choices that help define a species’ place in nature. As the old adage goes, you are what you eat. Teeth are important because they can help us understand relationships between animals in the past and the worlds around them, and about their—and our—evolution.

Why do we have so many problems with our teeth today? Why do we get cavities, require braces, and have impacted wisdom teeth?

PSU: Think about how extraordinary your teeth are. They have to break food, without being broken themselves, up to millions of times over your lifetime. And they have to do it built from the very same raw materials as the foods you are eating. Nature is truly an inspired engineer, and it’s remarkable they last as long and function as well as they do. But they’re not perfect. Most of us today get cavities, and many of us have crooked front teeth, and impacted wisdom teeth. This is largely because of our diets. We eat mostly soft foods, loaded with highly-processed carbohydrates, especially refined sugars. Cavities form by erosion from acids produced by plaque bacteria. Feeding those bacteria diets high in carbohydrates, especially sugars, means more cavities. Also, when we eat soft foods as children, we don’t exercise our jaws enough to stimulate the growth they need to make room for all our teeth. The result is crowded lower incisors, uppers that jut out over the lowers in the front of the mouth, and impacted third molars in the back. It’s not that our teeth are too big for our jaws, it’s that our jaws don’t grow long enough to accommodate all our teeth. Most traditional foragers that eat tougher or harder foods have longer jaws, and so don’t suffer the sorts of orthodontic problems the rest of us have.

Do other species have these problems? If not, why are we so different?

PSU: I’ve seen cavities and evidence for gum disease in some non-human primates, particularly in species that eat a lot of fleshy, sugary fruit, but they’re much rarer than in us. There are very few early human fossils that provide evidence of dental disease in our distant past either. Again, it seems to be a mismatch between our diets today, and the foods that we evolved to eat. Our teeth are not designed for hamburgers and French fries, nor to be bathed in milkshake. If you want to see evidence of that mismatch, just smile and look in a mirror.

What was your motivation for writing a popular science book?

PSU: My PhD dissertation was 654 pages, mostly focused on a quarter of a square millimeter of the surface of some incisor teeth. Most academics are so narrow in their research focus that it can be difficult to see the forest for the trees. I wrote this book to give myself the big picture, to give me an appreciation of the larger context into which my own work fits. Also, no more than half a dozen people actually read my dissertation cover to cover, and that includes my mother. Academics often feel like they’re speaking, but no one is listening. I wanted to reach a larger audience. This book at first glance seems to be about teeth – but it’s really about the biospheric buffet, and how environmental change over deep time swapped out items and choices available to our distant ancestors. The take-home message is that large-scale climate swings winnowed out the pickier eaters among us, and drove our evolution. Teeth are our window through which to see it. The most important message here is that climate changes, and species have to change to accommodate or die. That’s why we’re here. It’s a timely, important lesson.

As a scientist who has spent the last three decades studying evidence for the evolution of human diet, what do you think of today’s “Paleolithic diet” trend? And what was the ancestral human diet, anyway?

PSU: I’m not a fan. I like pizza and bagels too much. Still, there’s little doubt that our ancestors did not eat such things; so it makes sense that a discordance between the foods we evolved to consume and what we fuel ourselves with today can wreak havoc on our bodies. Try putting diesel in a car built to run on regular gasoline (actually, don’t). And people do lose weight when they cut refined carbohydrates and processed sugars from their diets. We could well benefit from eating more like our Stone Age ancestors, with menus like those in some popular diet books—you know, spinach salads with avocado, walnuts, diced turkey and the like. I am not a nutritionist, and cannot speak with authority about the nutritional costs of benefits of Paleolithic diets—but I can address their evolutionary underpinnings. Think about it this way. Any diet that drains the body of fat reserves means not meeting daily caloric needs. It is difficult to believe that nature would select for us to eat only foods that don’t provide the nutrients required to maintain the body. In fact, the whole idea of the Paleolithic diet is problematic. Even if we could (and we can’t) reconstruct the glycemic load, fatty acid, macro- and micronutrient composition, acid/base balance, sodium/potassium ratio, and fiber content of foods eaten at a moment in time in the past, the information would be meaningless for planning a menu. All these nutrients varied with food availability over space and time, as items on the biospheric buffet table were swapped in and out, so focusing on a single point in our evolution is futile. We’ve been a work in progress for millions of years. What was the ancestral human diet? The question itself makes no sense.

Peter S. Ungar is Distinguished Professor and director of the Environmental Dynamics Program at the University of Arkansas. He is the author of Teeth: A Very Short IntroductionMammal Teeth: Origin, Evolution, and Diversity and Evolution’s Bite: A Story of Teeth, Diet, and Human Origins.

The Great Mother—Jackets throughout the years

Goddess, monster, gate, pillar, tree, moon, sun, vessel, and every animal from snakes to birds: the maternal has been represented throughout history as both nurturing and fearsome, a primordial image of the human psyche. In celebration of Mother’s Day, we dipped into the archives for a tour of the various covers of a landmark book, Erich Neumann’s The Great Mother.

Oscar Fernandez: A Healthier You is Just a Few Equations Away

This post appears concurrently on the Wellesley College Summer blog.

How many calories should you eat each day? What proportion should come from carbohydrates, or protein? How can we improve our health through diets based on research findings?

You might be surprised to find that we can answer all of these questions using math.  Indeed, mathematics is at the heart of nutrition and health research. Scientists in these fields often use math to analyze the results from their experiments and clinical trials.  Based on decades of research (and yes, math), scientists have developed a handful of formulas that have been proven to improve your health (and even help you lose weight!).

So, back to our first question: How many calories should we eat each day?  Let’s find out…

Each of us has a “total daily energy expenditure” (TDEE), the total number of calories your body burns each day. Theoretically, if you consume more calories than your TDEE, you will gain weight. If you consume less, you will lose weight. Eat exactly your TDEE in calories and you won’t gain or lose weight.

“Great! So how do I calculate my TDEE?” I hear you saying. Good question. Here’s a preliminary answer:

TDEE = RMR + CBE + DIT         (1)                                                                                                                                                                  

Here’s what the acronyms on the right-hand side of the equation mean.

  • RMR: Your resting metabolic rate, roughly defined as the number of calories your body burns while awake and at rest
  • CBE: The calories you burned during the day exercising (including walking)
  • DIT: Your diet’s diet-induced thermogenesis, which quantifies what percentage of calories from dietary fat, protein, and carbohydrates are left over for your body to use after you ingest those calories

So, in order to calculate TDEE, we need to calculate each of these three components. This requires very precise knowledge of your daily activities, for example: what exercises you did, how many minutes you spent doing them, what foods you ate, and how much protein, carbohydrates, and dietary fat these foods contained. Luckily, nutrition scientists have developed a simpler formula that takes all of these factors into account:

    TDEE = RMR(Activity Factor) + 0.1C.         (2)

Here C is how many calories you eat each day, and the “Activity Factor” (below) estimates the calories you burn through exercise:

 

Level of Activity Activity Factor
Little to no physical activity 1.2
Light-intensity exercise 1-3 days/week 1.4
Moderate-intensity exercise 3-5 days/week 1.5
Moderate- to vigorous-intensity exercise 6-7 days/week 1.7
Vigorous daily training 1.9

 

As an example, picture a tall young man named Alberto. Suppose his RMR is 2,000 calories, that he eats 2,100 calories a day, and that his Activity Factor is 1.2. Alberto’s TDEE estimate from (2) would then be

TDEE = 2,000(1.2) + 0.1(2,100) = 2,610.

Since Alberto’s caloric intake (2,100) is lower than his TDEE, in theory, Alberto would lose weight if he kept eating and exercising as he is currently doing.

Formula (2) is certainly more user-friendly than formula (1). But in either case we still need to know the RMR number. Luckily, RMR is one of the most studied components of TDEE, and there are several fairly accurate equations for it that only require your weight, height, age, and sex as inputs. I’ve created a free online RMR calculator to make the calculation easier: Resting Metabolic Heart Rate. In addition, I’ve also created a TDEE calculator (based on equation (2)) to help you estimate your TDEE: Total Daily Energy Expenditure.

I hope this short tour of nutrition science has helped you see that mathematics can be empowering, life-changing, and personally relevant. I encourage you to continue exploring the subject and discovering the hidden math all around you.

Oscar E. Fernandez is assistant professor of mathematics at Wellesley College. He is the author of Everyday Calculus: Discovering the Hidden Math All around Us and The Calculus of Happiness: How a Mathematical Approach to Life Adds Up to Health, Wealth, and Love. He also writes about mathematics for the Huffington Post and on his website, surroundedbymath.com.