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.

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!

Bird Fact Friday – Why does the Toucan have such a large, colorful bill?

From page 273 in The New Neotropical Companion:

Photo by James Adams

Perhaps more than any other kind of bird, toucans symbolize the American tropics. With a prominent boat-shaped, colorful bill almost equal in length to the body, the toucan silhouette is instantly recognizable. Toucans’ seemingly oversize bills are actually lightweight. Colorful patterns adorn most ramphastid bills; they may possibly be used for signaling in mate selection. Recent studies on the Toco Toucan have demonstrated that the birds are able to radiate excess heat from their long, vascularized bills. In a paper by Glenn Tattersall and colleagues, the researchers conclude that the toucan bill is “relative to its size, one of the largest thermal windows in the animal kingdom, rivaling elephants’ ears in its ability to radiate body heat.”

Toko Toucan. Photo by John Kricher

The New Neotropical Companion
John Kricher
Chapter One

The New Neotropical Companion is the completely revised and expanded edition of a book that has helped thousands of people to understand the complex ecology and natural history of the most species-rich area on Earth, the American tropics. Featuring stunning color photos throughout, it is a sweeping and cutting-edge account of tropical ecology that includes not only tropical rain forests but also other ecosystems such as cloud forests, rivers, savannas, and mountains. This is the only guide to the American tropics that is all-inclusive, encompassing the entire region’s ecology and the amazing relationships among species rather than focusing just on species identification.

The New Neotropical Companion is a book unlike any other. Here, you will learn how to recognize distinctive ecological patterns of rain forests and other habitats and to interpret how these remarkable ecosystems function—everything is explained in clear and engaging prose free of jargon. You will also be introduced to the region’s astonishing plant and animal life.

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.

Tuesday’s Trot – Icelandic Horse

Good news for all the horse lovers out there! Starting this week in our new “Tuesday’s Trot” feature, we’re highlighting some fun facts about various horses from Horses of the World. Kicking it off today is the Icelandic Horse.

From page 32 in Horses of the World:

Iceland has only one breed of horse, but what a breed it is! The Icelandic is one of the most amazing horses in the world, with its incredible variety of colors and its five gaits. Iceland has developed its own equestrian culture, and a specific saddle for it. The horse plays a major role in Icelandic mythology and its great sagas. Some Europeans use the term “pony” to describe this small horse, but the term “pony” isn’t used in Iceland, just as it isn’t in many countries of the world.

Icelandic equitation is based on the breed’s specific gaits (here, the tölt).

 

Icelandic Saddle

5 things you should know about the Icelandic Horse:

1. The Icelandic is particularly ancient and pure due to the ban, since 982, on importing new horses into Iceland. The horses that leave Iceland don’t return. The Icelandic has thus not undergone any crossing.

2. Adapted to an extreme climate, the Icelandic is very resilient and very hardy. Many horses spend the harsh winter outdoors. It is an easy keeper.

3. The Icelandic is a very intelligent horse; it is calm and friendly, but independent and energetic.

4. One of the unique characteristics of the Icelandic is its additional gaits, the tölt and the flying amble. It is one of the only gaited horses native to Europe, as European breeders have eliminated this characteristic in many breeds.

5. A horse with a strong identity, the Icelandic has been introduced successfully into many countries beginning in the twentieth century. There are currently more than 180,000 Icelandics throughout the world.

 

Horses of the World
Élise Rousseau
Illustrated by Yann Le Bris
Translated by Teresa Lavender Fagan
Sample Entry

Horses of the World is a comprehensive, large-format overview of 570 breeds of domestic and extant wild horses, including hybrids between the two and between domestic breeds and other equids, such as zebras. This beautifully illustrated and detailed guide covers the origins of modern horses, anatomy and physiology, variation in breeds, and modern equestrian practices. The treatment of breeds is organized by country within broader geographical regions—from Eurasia through Australasia and to the Americas. Each account provides measurements (weight and height), distribution, origins and history, character and attributes, uses, and current status. Every breed is accompanied by superb color drawings—600 in total—and color photographs can be found throughout the book.

Describing and depicting every horse breed in existence, Horses of the World will be treasured by all who are interested in these gorgeous animals.

 

A sneak peek at BIG PACIFIC, companion to upcoming PBS series

The companion five-part series on PBS: Big Pacific will air Wednesdays on PBS, June 21-July 19, 2017

The Pacific Ocean covers one-third of Earth’s surface—more than all of the planet’s landmasses combined. It contains half of the world’s water, hides its deepest places, and is home to some of the most dazzling creatures known to science. The companion book to the spectacular five-part series on PBS produced by Natural History New Zealand, Big Pacific by Rebecca Tansley breaks the boundaries between land and sea to present the Pacific Ocean and its inhabitants as you have never seen them before.

Illustrated in full color throughout, Big Pacific blends a wealth of stunning Ultra HD images with spellbinding storytelling to take you into a realm teeming with exotic life rarely witnessed up close—until now. Providing an unparalleled look at a diverse range of species, locations, and natural phenomena, Big Pacific is truly an epic excursion to one of the world’s last great frontiers. Take a sneak peek here:

 

 

More than superstition: Happy Groundhog Day!

The groundhog may have no talent for predicting the arrival of spring, but it surely can enlighten us on animals’ reactions to changing weather patterns. According to biologist Daniel T. Blumstein, celebrating Groundhog Day is about more than a superstition. In the Washington Post, he notes, “Understanding how individual groundhogs respond to environmental change is essential if we want to predict how animals will react to global warming and other human-driven habitat shifts.”

And no worries if Punxsutawney Phil sees his shadow on Groundhog Day, after all, if winter comes, can spring be far behind?

To know more about this mysterious mammal, check out Roland W. Kays and Don E. Wilson’s book Mammals of North America, an indispensable guide for amateur naturalists and professional zoologists alike.


Mammals of North America
Second Edition
Roland W. Kays & Don E. Wilson
Introduction
Mammals of North America APP

Covering 20 species recognized since 2002 and including 13 new color plates, this fully revised edition of Mammals of North America illustrates all 462 known mammal species in the United States and Canada—each in beautiful color and accurate detail. With a more up-to-date species list than any other guide, improved facing-page descriptions, easier-to-read distribution maps, updated common and scientific names, and track and scat illustrations, this slim, light, and easy-to-use volume is the must-have source for identifying North American mammals.

 

 

Bird Fact Friday — Not so bird brained after all…

From page 161 of Bird Brain:

Bird Brain by Nathan Emery makes the case that birds are not as devoid of intelligence as has previously been thought. In fact, some can even be considered as smart as apes and dolphins. This concludes our Bird Fact Friday feature. Stay tuned for Horse Fact Friday starting in the new year!

Bird Brain
An Exploration of Avian Intelligence
Nathan Emery
With a foreword by Frans de Waal
Introduction

EmeryBirds have not been known for their high IQs, which is why a person of questionable intelligence is sometimes called a “birdbrain.” Yet in the past two decades, the study of avian intelligence has witnessed dramatic advances. From a time when birds were seen as simple instinct machines responding only to stimuli in their external worlds, we now know that some birds have complex internal worlds as well. This beautifully illustrated book provides an engaging exploration of the avian mind, revealing how science is exploding one of the most widespread myths about our feathered friends—and changing the way we think about intelligence in other animals as well.

Bird Brain looks at the structures and functions of the avian brain, and describes the extraordinary behaviors that different types of avian intelligence give rise to. It offers insights into crows, jays, magpies, and other corvids—the “masterminds” of the avian world—as well as parrots and some less-studied species from around the world. This lively and accessible book shows how birds have sophisticated brains with abilities previously thought to be uniquely human, such as mental time travel, self-recognition, empathy, problem solving, imagination, and insight.

Written by a leading expert and featuring a foreword by Frans de Waal, renowned for his work on animal intelligence, Bird Brain shines critical new light on the mental lives of birds.

Bird Fact Friday – Birds storing food

From page 148 of Bird Brain:

Among social birds who cache their food, it is difficult to keep their hiding places a secret from other birds in their group. To get around this, they will move caches around to make the final hiding place difficult to determine. This strategy may have occurred accidentally in the past and resulted in a greater yield of recovered caches, or it may be a result of a deliberate attempt to deceive potential thieves.

Bird Brain
An Exploration of Avian Intelligence
Nathan Emery
With a foreword by Frans de Waal
Introduction

EmeryBirds have not been known for their high IQs, which is why a person of questionable intelligence is sometimes called a “birdbrain.” Yet in the past two decades, the study of avian intelligence has witnessed dramatic advances. From a time when birds were seen as simple instinct machines responding only to stimuli in their external worlds, we now know that some birds have complex internal worlds as well. This beautifully illustrated book provides an engaging exploration of the avian mind, revealing how science is exploding one of the most widespread myths about our feathered friends—and changing the way we think about intelligence in other animals as well.

Bird Brain looks at the structures and functions of the avian brain, and describes the extraordinary behaviors that different types of avian intelligence give rise to. It offers insights into crows, jays, magpies, and other corvids—the “masterminds” of the avian world—as well as parrots and some less-studied species from around the world. This lively and accessible book shows how birds have sophisticated brains with abilities previously thought to be uniquely human, such as mental time travel, self-recognition, empathy, problem solving, imagination, and insight.

Written by a leading expert and featuring a foreword by Frans de Waal, renowned for his work on animal intelligence, Bird Brain shines critical new light on the mental lives of birds.

Bird Fact Friday – Romancing a mate

From page 146 of Bird Brain:

Food sharing is a behavior at the heart of many avian pair bonds. Some males offer a potential partner a nuptial gift as a display of their ability to provide. In some cases, gift-giving continues throughout the pair’s life as a means of solidifying their bond.

Bird Brain
An Exploration of Avian Intelligence
Nathan Emery
With a foreword by Frans de Waal
Introduction

EmeryBirds have not been known for their high IQs, which is why a person of questionable intelligence is sometimes called a “birdbrain.” Yet in the past two decades, the study of avian intelligence has witnessed dramatic advances. From a time when birds were seen as simple instinct machines responding only to stimuli in their external worlds, we now know that some birds have complex internal worlds as well. This beautifully illustrated book provides an engaging exploration of the avian mind, revealing how science is exploding one of the most widespread myths about our feathered friends—and changing the way we think about intelligence in other animals as well.

Bird Brain looks at the structures and functions of the avian brain, and describes the extraordinary behaviors that different types of avian intelligence give rise to. It offers insights into crows, jays, magpies, and other corvids—the “masterminds” of the avian world—as well as parrots and some less-studied species from around the world. This lively and accessible book shows how birds have sophisticated brains with abilities previously thought to be uniquely human, such as mental time travel, self-recognition, empathy, problem solving, imagination, and insight.

Written by a leading expert and featuring a foreword by Frans de Waal, renowned for his work on animal intelligence, Bird Brain shines critical new light on the mental lives of birds.

Bird Fact Friday – Master toolmakers

From page 120 of Bird Brain:

New Caledonian crows sculpt their own tools from raw materials. The first type is made from the strong and flexible Pandanus leaf. A crow bites one end of an individual leaf and pulls off a long strip, detaching the piece. The tool has a sharpened point at one or both ends, and, depending on the leaf, a jagged edge. It is used to catch certain kinds of prey.

Bird Brain
An Exploration of Avian Intelligence
Nathan Emery
With a foreword by Frans de Waal
Introduction

EmeryBirds have not been known for their high IQs, which is why a person of questionable intelligence is sometimes called a “birdbrain.” Yet in the past two decades, the study of avian intelligence has witnessed dramatic advances. From a time when birds were seen as simple instinct machines responding only to stimuli in their external worlds, we now know that some birds have complex internal worlds as well. This beautifully illustrated book provides an engaging exploration of the avian mind, revealing how science is exploding one of the most widespread myths about our feathered friends—and changing the way we think about intelligence in other animals as well.

Bird Brain looks at the structures and functions of the avian brain, and describes the extraordinary behaviors that different types of avian intelligence give rise to. It offers insights into crows, jays, magpies, and other corvids—the “masterminds” of the avian world—as well as parrots and some less-studied species from around the world. This lively and accessible book shows how birds have sophisticated brains with abilities previously thought to be uniquely human, such as mental time travel, self-recognition, empathy, problem solving, imagination, and insight.

Written by a leading expert and featuring a foreword by Frans de Waal, renowned for his work on animal intelligence, Bird Brain shines critical new light on the mental lives of birds.

Bird Fact Friday – How have bird eyes evolved?

From page 66 of Bird Brain:

Compared to most mammals, bird eyes are highly complex. They contain four color photoreceptors, or cones, capable of aiding the perception of a much wider frequency range of light wavelengths. Birds are even able to see across the entire visible color spectrum, including colors in the invisible spectrum that humans cannot see unaided. There are important reasons why birds have evolved this way, and Nathan Emery describes them in Bird Brain.

Bird Brain
An Exploration of Avian Intelligence
Nathan Emery
With a foreword by Frans de Waal
Introduction

EmeryBirds have not been known for their high IQs, which is why a person of questionable intelligence is sometimes called a “birdbrain.” Yet in the past two decades, the study of avian intelligence has witnessed dramatic advances. From a time when birds were seen as simple instinct machines responding only to stimuli in their external worlds, we now know that some birds have complex internal worlds as well. This beautifully illustrated book provides an engaging exploration of the avian mind, revealing how science is exploding one of the most widespread myths about our feathered friends—and changing the way we think about intelligence in other animals as well.

Bird Brain looks at the structures and functions of the avian brain, and describes the extraordinary behaviors that different types of avian intelligence give rise to. It offers insights into crows, jays, magpies, and other corvids—the “masterminds” of the avian world—as well as parrots and some less-studied species from around the world. This lively and accessible book shows how birds have sophisticated brains with abilities previously thought to be uniquely human, such as mental time travel, self-recognition, empathy, problem solving, imagination, and insight.

Written by a leading expert and featuring a foreword by Frans de Waal, renowned for his work on animal intelligence, Bird Brain shines critical new light on the mental lives of birds.