. . . it is often through the extraordinary that the philosopher gets the most searching glimpses into the heart of the mystery of theordinary. Truly it has been said, facts are stranger than ﬁction. —George M. Gould and Walter L. Pyle Anomalies and Curiosities of Medicine (1896)
CONTENTS - List of Illustrations xi Introduction 3 O ne A Pa rliame nt o f Mo nste rs On the Breadth and Scope of Developmental Anomalies 15 Two A r re sting Fe atu re s Development is All about Time 53 Three D o th e Lo c o motio n How We Learn to Move Our Bodies 105 Fo u r Life and LimbHow Limbs are Made, Lost, Replaced, and Transformed 141 Five Anyth ing G oe s When it Comes to Sex, Expect Ambiguity 191 Epi lo g u e M onstro u s Be h avio rWe Still Have Much to Learn from the Odd and Unusual 251 Acknowledgments 257 Notes 259 Sources and Suggested Reading 283 Author Index 309 Subject Index 315 IX
ILLUSTRATIONS - 7 Drawings of conjoined twins adapted from Alberch (1989). With permission from Elsevier.20 Photograph of Lakshmi Tatma used with permission from BARM/Fame. Photograph of Vishnu used with permis- sion from Andrew Morse Alamy.25 Two drawings from Paré’s On monsters and marvels (1573/1982) used with permission from Librairie Droz SA.28 Photograph of Laloo and his parasitic twin from Gould and Pyle’s Anomalies and curiosities of medicine (1896). Reprinted with permission from Elsevier.56 Photograph of elephant skull, courtesy of African Hunter Magazine (ﬁshunt@zol.co.zw). XI
XII S ILLUSTRATIONS58 Two drawings from Wilder’s (1908) “Cosmobia” series. Reprinted with permission from Wiley-Liss, Inc., a subsidiary of John Wiley and Sons, Inc.59 Two drawings from Wilder’s (1908) “Cosmobia” series. Reprinted with permission from Wiley-Liss, Inc., a subsidiary of John Wiley and Sons, Inc.61 Enlargement of Wilder’s (1908) sketch of a cylcopic infant. Reprinted with permission of Wiley-Liss, Inc., a subsidiary of John Wiley and Sons, Inc. Photograph of young elephant used with permission from Corbis Super RF/Alamy.62 Photograph of elephant fetus from Gaeth et al. (1999) used with permission from the National Academy of Sciences, U.S.A. Photograph of embryonic mouse from Chiang et al. (1996) used with permission from Macmillan Publishers Ltd.; photograph courtesy of Dr. Chin Chiang.63 Photograph of Tlatilco ﬁgurine used with permission from The Art Archive/National Anthropological Museum of Mexico/Gianni Dagli Orti.64 Drawing of woman with diprosopia from Lesbre (1927). Photograph of kitten with diprosopia used with permission from Bucks County Courier Times/Jay Crawford.66 Wilder’s (1908) complete “Cosmobia” series. Reprinted with permission from Wiley-Liss, Inc., a subsidiary of John Wiley and Sons, Inc.
ILLUSTRATIONS s XIII89 Four drawings from Wilder’s (1908) “Cosmobia” series. Reprinted with permission from Wiley-Liss, Inc., a subsidiary of John Wiley and Sons, Inc.90 Drawings of conjoined human twins adapted from Spencer (2000). Reprinted with permission from Wiley-Liss, Inc., a subsidiary of John Wiley and Sons, Inc.97 Photographs of frog embryo and conjoined twinning in tadpoles, courtesy of John Gerhart.99 Photograph of dicephalic British grass snake, courtesy of the Federation of British Herpetologists.106 Poster depicting Johnny Eck, courtesy of the Johnny Eck Museum (johnnyeckmuseum.com).111 Photograph of Faith, the two-legged dog, courtesy of Chris Brown.129 Figure depicting the typical postures and body shapes of four rodent species adapted from Eilam (1997). Used with permission from The Company of Biologists Ltd.133 Figure depicting the typical postures of young jerboas adapted from Eilam and Shefer (1997). Used with permission from Wiley-Liss, Inc., a subsidiary of John Wiley and Sons, Inc. Drawing of skeleton of adult jerboa in the public domain.145 Photographs of young girl with amelia, courtesy of the Mütter Museum, College of Physicians of Philadelphia.148 Photograph and drawing of naked mole-rat, courtesy of Kenneth Catania.
XIV S ILLUSTRATIONS149 Photographs and drawing of star-nosed mole, courtesy of Kenneth Catania.154 Photograph of snake skeleton used with permission from Jupiterimages/Polka Dot/Alamy. Photograph of limbed reptile used with permission from Andy Crawford/ Dorling Kindersley.169 Photograph of mirror-image limb duplication in a frog adapted from Stopper et al. (2002). Reprinted with permission of Wiley-Liss, Inc., a subsidiary of John Wiley & Sons, Inc. Drawing of mirror-image limb duplication in a human adapted from Gould and Pyle’s Anomalies and curiosities of medicine (1896). Used with permission from Elsevier. 171 Photograph of long-toed salamander adapted from Johnson et al. (2006). Courtesy of Pieter Johnson. Used with per- mission from The Ecological Society of America. 173 Photograph of underside of turtle, courtesy of Stephen Burnett. 175 Drawings of a snapping turtle embryo by Kathy Brown- Wing. Courtesy of Ann Burke.177 Photograph of “fabulous unicorn” from Dove (1936). Reprinted with permission from the American Association for the Advancement of Science.179 Photograph of dung beetle pupa from Emlen et al. (2006). Courtesy of Doug Emlen.180 Photographs of scarab beetle species from Emlen et al. (2006). Courtesy of Doug Emlen. 232 Photographs of spotted hyena penis and clitoris from Glickman et al. (2006). Courtesy of Stephen Glickman. Reprinted with permission from Elsevier.242 Photographs of female and male anglerfish, courtesy of Ted Pietsch.
Introduction -Z oos have changed a lot since I was a child. Gone are the sterile, cramped cages and other overt signs of animalsin captivity, trapped, often alone, fed their required daily dietsbut little nourished in other ways, most of them disconnectedfrom the habitats—be they jungles or forests, mountains orsavannahs, rivers or seas, ice ﬂoes or swamps—in which theircounterparts in the wild are born and live their lives. The oldzoos could be sad places. They testiﬁed to the human proclivityto possess the exotic, the rare, and the unusual while managingto deplete them of their full curious richness by sticking themunder glass or behind bars or in a tiny pond, each an “exhibit”plainly labeled for the viewing public to see: mountain gorilla,Asian elephant, Emperor penguin, python. 3
4 S FREAKS OF NATURE Most zoos today are certainly more humane and morerespectful of the animals in their charge. But even the best ofzoos now, with their naturalistic surroundings and cleverly dis-guised barriers, are still not ideal settings for observing therichness of animal life in all its forms. They can provide onlya rough-and-ready sketch of an animal—its size, shape, andcolor—and the basics of its movement. Moreover, becauseeach animal we see is meant to accurately represent the spe-cies to which it belongs, zoos aim to present us with the mostexquisite specimens possible—the archetypal Bear, Lion, andMonkey. Archetypes engender misperceptions. They feed the illusionthat, from the moment of conception, nature had a goal inmind. Breeders of pedigree dogs are prisoners of the arche-type, devoting incalculable time and energy to creating the per-fect Affenpinscher or Yorkshire terrier. In their world, eventhe slightest blemish is enough to banish a dog to permanentexile. The pursuit of perfection, canine or otherwise, inevitablybutts heads with reality. The world is messy, and nature isunwieldy, unpredictable, and vastly more imaginative than wecan ever truly capture—or ward off—with our blemish-freearchetypes. Left to its own devices, nature always takes excep-tion to the rule, undermines the archetype, and reminds us thatour ideas about what is natural and what we should do to correctnature’s “imperfections” are as sound as a sandcastle batteredby a rising tide. And nothing batters those ideas with more
INTRODUCTION s 5gusto, more shock and awe, than the creature in nature that ismalformed or otherwise anomalous: the freak. Unfortunate term, freak, but that and monster are the verycolloquialisms that scientists and philosophers have used todescribe the odd and the grotesque throughout history. Theseand similar terms have become common parlance as well, sayingmore about our overwrought fascination with the unexplainedand about our skewed notions of perfection than about oddlyformed individuals themselves. When applied to odd-lookinghuman beings, these words also say a lot about our desireto draw a sharp line between them and us. They are freaks.We, however, are just ordinary folks who popped out of thewomb perfectly formed, all ﬁngers and toes and everything elseaccounted for and in the right place, shocking no one because,after all, that’s how our bodies are supposed to look. I recently introduced some friends, via computer, to Abigailand Brittany Hensel, the world’s most famous conjoined twins.The Hensels are the rarest of the rare—conjoined twins with twoheads but just one body. Watching these girls swim, ride a bike,and dribble a basketball, my friends were as stunned as I was whenI ﬁrst saw them in action. One friend asked: How do they do that? In a world gone wobbly for archetypes, we cannot imaginehow these twins do that. We cannot imagine how their body andbehavior jibe. We do not have a clue how they have managedto function so well and even thrive, conjoined, since birth—orrather, since before birth. Amazing. We could never live that way.We could never do what they have to do to get by every day.
6 S FREAKS OF NATURE On the other hand, what we do is no less amazing after wepop out of the womb perfectly formed, all our parts where theyshould be, our single heads attached to our single bodies. Wefunction. How? Our mystiﬁcation at the Hensel twins and their ability toharmonize their uniquely assembled body parts is informative:It exposes how little we understand about physical growth anddevelopment, whether in individuals like Abigail and Brittany orin individuals who are normally constructed. It also exposes anunbalanced view that separates the anomalous from the normal,as though one descended inexplicably from outer space and theother was born fully developed according to prescribed earth-bound rules. Obviously, the Hensel twins are as earth-bound asthe rest of us, and that fact alone should tell us something aboutthe nature of nature. Nary an archetype in the picture, but surelya diversity of unique lives. It is the aim of this book to explore that diversity by focus-ing on some of its oddest representatives. It is also to con-join the worlds of the anomalous and the normal—to showhow the Hensel twins and others like them in the animalkingdom reveal the remarkable ﬂexibility inherent in all indi-vidual development, the intimate connection between devel-opment and evolution, and the nature of development itself.These “freaks,” through both their bodies and their behavior,point to underlying processes at work in nature that are atonce complex, wondrous, often peculiar, sometimes comical,and always perfectly natural. They have much to tell us about
INTRODUCTION s 7ourselves. For in the larger, unfolding scheme of things, weare all extraordinary, all strange—freaks every last one of us.Some of us just happen to be more notable, with a particularlyinteresting story to tell. ——As we look at developmental anomalies like the Hensel twins,few of us would think to ask: Who designed them that way? Certainlyno proponents of “intelligent design” would ask such a ques-tion, especially if they glanced at the conjoined twins—humanand minnow—depicted below. As we will see, there are manysuch anomalies that betray shared, ancient mechanisms, theirappearance alone challenging the notion of a competent andbenevolent Designer. Two-headed conjoined twins look similar in humans (left) and minnows (right). For their part, evolutionists argue that the natural worldonly appears well designed. They correctly point to the manyinstances where the constraints of evolutionary history havenecessitated imperfect, even absurd designs that are nonetheless
8 S FREAKS OF NATUREquite functional. For this reason, evolutionists appreciate errors.They understand, for example, that our eye’s blind spot reﬂectsa wiring ﬂaw that a competent designer would have avoided.Thus, we say that our eyes betray a process of apparent design—aprocess shaped by natural selection, constrained by history, andfar from ﬂawless. Blind spots and developmental anomalies present an instruc-tive contrast. Each signiﬁes error and imperfection. However,whereas the blind spot has become the darling of contemporaryevolutionists taking aim at “intelligent design,” these sameevolutionists have turned a blind eye to anomalies. For them,developmental anomalies are dysfunctional throwaways, incom-patible even with the notion of apparent design. To capture the signiﬁcance of blind spots and other designﬂaws, evolutionists have replaced the Designer with the tinkerer—“a tinkerer who does not know exactly what he is going to pro-duce but uses whatever he ﬁnds around him whether it be piecesof string, fragments of wood, or old cardboards”1—a usefulmetaphorical shift to be sure. As traditionally rendered,2 thetinkerer only makes incremental adjustments to slightly variableforms and decides which ones to keep. Not coincidentally, the metaphorical tinkerer ﬁts neatlywith the perspective favored by Charles Darwin and his closestadherents. According to them, small, random variations pro-vide the material on which natural selection acts. The result isa continuum of life forms that can be gently nudged in this or
INTRODUCTION s 9that direction to produce the seemingly separate species thatwe all recognize.3 But this incrementalist perspective, and thetinkerer that personiﬁes it today, does not quite capture thebiological signiﬁcance of conjoined twins and other develop-mental anomalies. Unlike the Darwinians, William Bateson saw the signiﬁcanceof anomalies. Writing at the end of the nineteenth century, heargued that the Darwinian notion that selection acts only onincremental variants was deeply ﬂawed. “Species,” Bateson ass-erted, “are discontinuous; may not the Variation by which Spe-cies are produced be discontinuous too?”4 Accordingly, Batesoncatalogued hundreds of extreme variants—monstrosities—withthe aim of elevating their status within evolutionary theory. Hebelieved, although at the time he could not prove, that mecha-nisms internal to the developing embryo—mechanisms inherentin the biological material—critically contribute to the varietyon display in nature. Despite Bateson’s best efforts, monstrosities—and the devel-opmental mechanisms presumed to give rise to them—werelargely ignored over the ensuing decades. Anomalies would bedismissed as evolutionary dead ends—unﬁt and irrelevant.Moreover, with the rise of Mendelian genetics at the beginningof the twentieth century, the processes of inheritance that, bymeans of genes, transmit characters or traits across generationswould come to be seen as qualitatively different from thoseinvolved in the development of those same characters.5 Because
10 S FREAKS OF NATUREof this “rupture” between genetic inheritance and developmen-tal mechanisms—between genotype, or the presumed inter-nal genetic constitution of an organism, and phenotype, theobservable characteristics of that organism; between nature andnurture—mainstream evolutionary biologists throughout mostof the twentieth century would come to view embryonic devel-opment as a process to be “largely dismissed as interesting butnot informative for evolutionary change . . . .”6 Even as these attitudes dominated the ﬁeld, some biologistsstill believed that conceiving of evolutionary change withoutfactoring in the developmental contributions to it produced anincomplete picture.7 But it took time for this developmentalperspective to reassert itself. Today, Bateson’s views are beingdusted off and reexamined,8 and the rupture between inher-itance and development is ﬁnally being mended. Indeed, inDevelopmental Plasticity and Evolution, Mary Jane West-Eberhardseeks nothing less than a new evolutionary synthesis of inheri-tance and development—one “that gives attention to both thetransmission and the expression of genes.”9 Her perspectiveis informed by the insights of Darwin, of course, but also ofBateson, who would have appreciated her section entitled InPraise of Anomalies. In that section, West-Eberhard writes: To see pattern and extremes in variation is to glimpse the world as seen by natural selection. It is not a world of uniformly tiny, mutationally based, or exclusively quantitative variants. Rather, it is one full of recurrent developmental anomalies
INTRODUCTION s 11 that vary in accord with the genetic makeup of individuals and also with their environmental circumstances.10She continues: Unusual variation is abnormal, at least in the sense of being rare, and sometimes even grotesque. But anomalies represent new options for evolution . . . .11 The “options” that anomalies offer are embedded withinthe mechanisms of development. Anomalies help us to glimpsethese mechanisms with a clarity that can be lost by focusing onwell-formed organisms alone. Consider again the picture of thetwo-headed humans and minnows. That such strikingly sim-ilar forms can arise in these distantly related species testiﬁesto the action of ancient developmental mechanisms. Moreover,as we will see, even extreme anomalies such as these can beproduced with surprising ease through the subtlest kinds ofdevelopmental adjustments. Thus, it is not difﬁcult to see howdiverse forms of life on our planet—including the novel andthe anomalous—could have emerged through the evolutionary“tweaking” of developmental mechanisms.12 The boundary between novelty and anomaly is a fuzzy one.After all, bodily forms considered anomalous in one species cansignify novelty in another. For example, some humans are bornwithout arms and legs, but all snakes are born that way. Wemay properly characterize limblessness as an anomalous featurein an individual human (in relation to other humans), but as a
12 S FREAKS OF NATUREnovel feature of snakes (in relation to other reptiles). But suchcharacterizations do not move us any closer to an appreciationof the shared developmental processes that underlie limbless-ness in humans and snakes. This book explores the biological signiﬁcance of devel-opmental anomalies of various sorts and, in so doing, shedslight on “the evolutionary implications of development and thedevelopmental implications of evolution.”13 Toward that end,we will ﬁrst consider the historical signiﬁcance of “freaks” and“monsters” and their role in the historically rocky relationshipbetween developmental and evolutionary perspectives. It is inthe context of that relationship that we will return to Darwinand Bateson to discuss their views in greater detail; we will alsomeet other key ﬁgures before and after them whose work hascontributed to the literature on this subject. Then we will lookat the core principles underlying development itself, in termsof bodily form and function and in terms of the developmentalmechanisms that give rise to them. Within that broad frame-work, we will also look at how anomalous forms can emerge fromeven subtle changes in the timing of embryonic developmen-tal processes and how both anomalous individuals—whetherconjoined, limbless, ambiguously gendered, or otherwise oddlyformed—and entire freakish species move about, interact with,and survive in the world. This is not a textbook, scholarly treatise, or historical survey,although it does draw extensively on both science and history todescribe what is known and not known about anomalous beings.
INTRODUCTION s 13I do not claim to present here a grand new theory. Rather, I aimto use developmental anomalies—in all their forms—as lever-age to help the reader gain perspective on a subject that evenexperts ﬁnd challenging. However, it is important to emphasizethat anomalies represent only one path through the complexterrain that is development and evolution. Thus, my choiceto focus here on anomalies is in part pedagogical, and in partprincipled: Anomalies are difﬁcult to ignore; they matter fordevelopment and they matter for evolution; they reveal hid-den capabilities and processes in individuals and groups, and inbodies and behaviors; and they are indispensable weapons in thebattle to break the spell of “designer thinking.”14 Thus, despitetheir characterization as errors of nature, the anomalous—whenproperly considered—force us to confront and correct thoseerrors in our thinking that often impede scientiﬁc insight andprogress. Our culture has its archetypes of beauty, intelligence, andathleticism—those ideal standards toward which many of usstrive. Archetypes, then, are creatures of our imagination thatcloud our conceptions of nature and waft like some hot-airballoon above the fray of the real world. But like ballast, thosecreatures that we see as odd, abnormal, defective, and freakishgive meaningful weight to the balloon and help us stay closeto solid ground. When we jettison them, we set ourselveshopelessly adrift on a journey of illusion.
ONE - A Parliament of Monsters On the Breadth and Scope of Developmental Anomalies Treasure your exceptions! . . . . Keep them always uncovered and in sight. Exceptions are like the rough brickwork of a growing building which tells that there is more to come and shows where the next construction is to be. William Bateson (1908) 1I n the spring of 1940 in the Dutch city of Utrecht, shortly before Hitler imposed his vision of Aryan perfection onHolland, a horribly malformed goat died. Much has been writ-ten about this goat,2 whose accidental death at just one year ofage cut short an extraordinary life. Because although this animalhad been born without forelegs, it had, despite its deformity,developed the ability to walk—upright. In Latin, such a crea-ture is called a lusus natura—a joke of nature. A freak, a monster.A violation of God’s intentions, of the natural order of things,of the evolutionary forces that shaped and reﬁned its ancestors.Clearly, this was one special goat. One also hears of humans overcoming birth defects andother disabilities in remarkable ways. Christy Brown, the 15
16 S FREAKS OF NATUREIrish artist and writer whose exceptional ability to cope withcerebral palsy was dramatized in the movie My Left Foot, providescompelling testimony to individual adaptability in the face ofsevere challenge. Perhaps even more compelling are wheelchair-bound athletes, such as those depicted in the documentary ﬁlmMurderball, whose competitive drive lifts them beyond theirphysical limitations. Such tales of triumph over physical challenge are amongour most treasured sources of inspiration. Much less treasured,however, are those anomalous productions of nature that chal-lenge our capacity for tolerance and understanding and that alltoo often horrify and disgust us. Still, we ﬁnd these odditiesundeniably fascinating. Why? Is it that our eyes are naturallydrawn to novelty, toward those objects that violate our expec-tations of how things ought to look? Also, why is our initialresponse so often one of fear and, all too often, cruelty? Perhapsit was fascination tinged with fear that once made acceptablethe corralling of freaks within the controlled environmentsof fairs and circuses. P. T. Barnum grasped this dynamic. Hewas a genius at extracting money from a Victorian public thatwas “mad about monstrosity.”3 Indeed, Barnum’s “specimens,”collected and displayed in his time, remain familiar to us by thenames that he bestowed upon them: Tom Thumb, the ElephantMan, the Bearded Lady, the Siamese Twins. Barnum’s crassness is countered by the sensitivity of DianeArbus, the great American photographer who memorablycaptured so many examples of human eccentricity. She once
A PARLIAMENT OF MONSTERS s 17commented that you “see someone on the street and essentiallywhat you notice about them is the ﬂaw.”4 Starting from thisperceptual bias, she focused on marginalized individuals,“[n]ot to ignore them, not to lump them together, but to watchthem, to take notice, to pay attention.”5 Her haunting photo-graphs—of giants and dwarves, twins and triplets, transvestites,nudists, and sadomasochists—permit the kind of reﬂection thatthe frenzy of a freak show cannot. As we gaze upon her subjects,we glimpse their individuality, not just the group to which theybelong. In the menagerie that Barnum paraded before a mesmerizedpublic and in the individuality that Arbus captured on ﬁlm, wegrasp the breadth and scope of freakishness. But as we will see inthis book, there is much more to learn about these marvels thaneither Barnum or Arbus realized. Beyond voyeurism and ﬁne art,freaks provide ready access to some essential truths about thedevelopment and evolution of animal form and behavior, andabout the individual potential within each of us. The lives at the heart of our story are tethered precariouslyto our planet. Like a polar bear stranded on a ﬂoating ice sheet,Earth sits alone in our solar system, a sign of life in a largelyfrigid wasteland. The emergence of life, then, is a rare event. Buteven the discovery of life beyond the perimeter of our planetwould not alter the fact that, in a universe comprising moredead space than living matter, every creature in our midst is afreak. We are, moreover, freaks with a history—a history whoseorigins can be traced to those ancestral moments when a few
18 S FREAKS OF NATUREsimple molecules marched across the gray zone that separatesanimate from inanimate matter. The hallmark of terrestrial life—and perhaps the hallmarkof life wherever we might ﬁnd it—is its diversity. There existmillions of species of bacteria, hundreds of thousands of speciesof plants, one million species of insects, and thousands of speciesof ﬁsh, amphibians, reptiles, birds, and mammals. But diversitydoes not stop at the boundaries that separate a human from achimpanzee, a lion from a tiger, or a canary from a cowbird.Within each species, we can ﬁnd remarkable diversity as well.To appreciate this, we need only consider the uniqueness ofeach human face or the distinctive color patterns of individ-ual zebras. But in addition to these “natural” variations amongmembers of a species, other kinds of variations are so extremethat they challenge our ability to comprehend their place withinthe natural order of things. So we can imagine the confusion that must have grippedour ancestors when, in a world where every birth would seema miracle, they confronted an infant born with a single torsosupporting two perfectly formed heads. Such seminal eventsin a small community would naturally be suffused with specialmeaning, and were often interpreted as the delivery of a messagefrom the gods. This ancient curiosity about the meaning ofmonstrous births is documented in a 4000-year-old cuneiformclay tablet, discovered near the Tigris River. The tablet listssixty-two human malformations, each assigned an omen, suchas death, destruction, or starvation. Little wonder, then, that the
A PARLIAMENT OF MONSTERS s 19word monster likely derives from the Latin word monere, meaningto warn. However, malformed infants were not always perceivedas mere conduits of communication from a godly realm.Occasionally, they became, if not gods themselves, then theinspiration for godly images.6 For example, Janus, the Romangod of gates and doors—of beginnings and endings—comprisestwo male heads, fused at the back, each face gazing metaphor-ically into the past and the future. Janus’s seemingly mythicalanatomy eerily mirrors those real-world conjoined twins thathave fused heads with oppositely oriented faces. Even Atlas, that imposing ﬁgure of Greek mythology,forced by Zeus to carry the world on his shoulders, may havebeen inspired by the appearance of an infant with a particularmalformation of early development.7 In this disorder, an abnor-mal gap in the back of the skull enables the growth, calledan encephalocele, of the underlying membranes and brain tissue,resulting in a bulbous mass of tissue resembling a globe perchedon the shoulders. Similar embryological parallels may underlieother mythological creatures, such as mermaids and cyclops. But one will search in vain for a simple and straightfor-ward narrative detailing the social reaction to monstrous birthsthroughout human history. Children with congenital malfor-mations may have inspired the sacred imagery for Atlas andJanus, but they also stirred a secular disgust that often resultedin their death—in ancient Rome they were drowned in theTiber River.8 More recently, the life of an eight-limbed Indian
Lakshmi Tatma (left) in 2007 before the surgery to remove her extra limbs. The multi-limbed Hindu god, Vishnu (right).girl may have been spared by portentous timing: she was bornon the very day set aside to celebrate Vishnu, the multi-limbedHindu god. Such has been the discordant response of ourspecies to the monstrous: fascination and fear, admiration andcontempt, consecration and desecration. Because there have always been too many sinners and notenough monsters, monstrous births were never easily pitchedto the people as punishment for individual moral failings.Moreover, the fact that domestic animals also produce mon-strous births made it more difﬁcult for religious leaders to pointthe ﬁnger of blame at human parents of monstrous infants.Rather, more typically and more effectively, these tragic eventswere cast in a symbolic light—as signs that God was payingattention to our activities and was not at all pleased with whatHe saw. Thus, by encouraging us to reﬂect on our behavior,monsters were meant to move us away from sin. Their use assymbols emerged precisely because communities were smalland each monstrous birth was so unusual. But as communitiesgrew, as in Europe, monstrous births were increasingly frequent,thereby diluting them of their uniqueness and signiﬁcance.
A PARLIAMENT OF MONSTERS s 21 The advent of printing had a particularly dramatic impact onchanging attitudes toward monsters. For example, in ElizabethanEngland during the sixteenth and seventeenth centuries, birthannouncements of the monstrous variety were often printedin verse form on single sheets of paper—called broadsides—andadvertised to villagers and town folk through song.9 The broad-sides conveyed accurate information about each birth, oftenincluding detailed family information and illustrations of thedeformed children. For the children and their parents, celeb-rity status soon followed and so did compensation from thehundreds of paying visitors encouraged by the broadsides to seethese families for themselves. Even if some viewed the infants asproper punishment for the moral decrepitude of their parents,that did not stop them from paying the price of admission.10 When parents began taking their “show” on the road, they wereable to reach a broader audience. This market for monsters wouldexpand during the eighteenth and nineteenth centuries, when theEuropean and American publics’ passion for monsters reached itszenith. William Wordsworth, the English romantic poet, capturedthis passion in his autobiographical collection, The Prelude. Writingin the early 1800s, Wordsworth described the Bartholomew Fair,held near London each year at the end of August: All moveables of wonder, from all parts, Are here—Albinos, painted Indians, Dwarfs, The Horse of knowledge, and the learned Pig, The Stone-eater, the man that swallows ﬁre, Giants, Ventriloquists, the Invisible Girl,
22 S FREAKS OF NATURE The Bust that speaks and moves its goggling eyes, The Wax-work, Clock-work, all the marvellous craft Of modern Merlins, Wild Beasts, Puppet-shows, All out-o’-the-way, far-fetched, perverted things, All freaks of nature, all Promethean thoughts Of man, his dulness, madness, and their feats All jumbled up together, to compose A Parliament of Monsters. Today, the thought of such spectacles and the crowds thatﬂocked to them appall us. We have lost our taste for the exploi-tation of the unusual. Or so we like to tell ourselves. H I T C H ES U NDER HEAV ENIn a culture where God was credited for all His creations, monsterswere to be counted among them. But as monsters became morefamiliar to common folk and scholars during the sixteenth cen-tury and beyond, it became increasingly difﬁcult to see in themthe handiwork of God. No longer isolated and rare, monstersdemanded explanation. A science of monstrosity was on thehorizon. In 1573, a French surgeon named Ambroise Paré publishedOn Monsters and Marvels. This book, considered by many histo-rians to be a watershed in the scientiﬁc discussion of monsters,was notable for its author’s focus on the causes of monstrous
A PARLIAMENT OF MONSTERS s 23births. However, as the opening passage of Paré’s book makesclear, he could not entirely shed his links with the prescientiﬁcpast: There are several things that cause monsters. The ﬁrst is the glory of God. The second, his wrath. The third, too great a quantity of seed. The fourth, too little a quantity. The ﬁfth, the imagination. The sixth, the narrowness or smallness of the womb. The seventh, the indecent posture of the mother, as when, being pregnant, she has sat too long with her legs crossed, or pressed against her womb. The eighth, through a fall, or blows struck against the womb of the mother, being of child. The ninth, through hereditary or accidental illnesses. The tenth, through rotten or corrupt seed. The eleventh, through mixture or mingling of seed. The twelfth, through the artiﬁce of wicked spital beggars. The thirteenth, through Demons and Devils.11 Note the curious mix of the material and the spiritual, ofhigh-minded moral judgment and mundane physical cause.In addition, his focus on early development—from fertiliza-tion through birth—is striking. But this focus could not com-pensate for his ignorance about development. Thus, Paré mayhave been interested in understanding the causes of monstrous
24 S FREAKS OF NATUREbirths—indeed, he organized his book around that theme—buthe was not equipped to do so. Paré’s distinction between monsters and marvels clearlyplaces him in an earlier age. As he described them, monsterswere “things that appear outside the course of Nature . . . , suchas a child who is born with one arm, another who will havetwo heads.”12 In contrast, marvels were “things which happenthat are completely against Nature as when a woman will givebirth to a serpent, or to a dog.” In other words, in a worldtypiﬁed by the natural, monsters were unnatural and marvelssupernatural.13 Hampered by a limited understanding of biology, Paréwas trying to make sense of the disparate observations andillustrations of others, many of them inaccurate and unre-liable. Not surprisingly, then, no obvious biological basisexists for Paré’s distinction between monsters and marvels.Certainly, Paré’s scheme is not reducible to a simple divisionbetween the biologically plausible and implausible. Such adivision makes no sense. For example, the birth of an oth-erwise normal dog to a human female is just as biologicallyimplausible as the birth of a human-dog hybrid, and yetParé distinguished between the two, classifying the formeras a marvel and the latter as a monster. He even recounts asfact the birth of a centaur-like monster, supposedly bornin 1493, whose upper torso resembled, “from the navel up,”its human mother and whose lower parts derived from itscanine father.14
Drawings of a child purported to have been born in 1493 to a human mother and canine father (left) and a man “from whose belly another man issued” (right). As we will see, the individuals who were to lay the ground-work for a modern science of developmental malformationwould dispense with Pare’s distinction between monsters andmarvels. As for Paré, we should forgive his naiveté. After all,many of the creatures illustrated in his book seem just as fan-tastic as centaurs but, as we now know, actually exist: Humanswith two heads and a plethora of limbs exist, as do “two twingirls joined together by their foreheads,”15 a man “from whosebelly another man issued,”16 and individuals with a normallysized head and torso but with grotesquely foreshortened armsand legs. Without a solid scientiﬁc foundation upon which tosift evidence, Paré’s judgment was a bit shaky.
26 S FREAKS OF NATURE Despite his shortcomings, Paré bridges our ancient andmodern fascination with monsters. Soon after his work, marvelswould disappear from the discussion and monsters would cometo be viewed as mistakes, errors, slips, and defects. Writing in1616, forty-three years after Paré, the Italian scholar FortunioLiceti clearly enunciated this break with the past. Unlike Paré,Liceti had no use for marvels and, moreover, he moved conﬁ-dently to expunge any hint of the supernatural from the worldof monsters: A monster is a being under heaven that provokes in the observer horror and astonishment by the incorrect form of its mem- bers, and is produced rarely, begotten, by virtue of a secondary plan of nature, as a result of some hitch in the causes of its origin.17 Going even further, he added: “It is unbelievable thatGod produces monsters in order to warn men of imminentcatastrophes.”18 Uncovering the “hitch” that might move a developing ani-mal toward “a secondary plan of nature” required a science thatwas not yet available to Liceti. Two hundred years later, in thelate eighteenth century, Etienne Geoffrey Saint-Hilaire, theFrench anatomist and natural historian, founded such a science,and it was his scientist son, Isidore Geoffrey Saint-Hilaire, whogave this ﬁeld its name: teratology, meaning literally the study ofmonsters (although today the term refers to the investigation of
A PARLIAMENT OF MONSTERS s 27congenital malformations, particularly those caused by environ-mental insults). Etienne’s initial goal was to classify monstrousforms in the same way that, earlier in the century, Carl Linnaeushad classiﬁed nonmonstrous forms. As Isidore described hisfather’s perspective: Monsters are not sports of nature; their organization is subject to rules, to rigorously determined laws, and these rules, these laws, are identical with those that regulate the animal series; in a word, monsters are also normal beings; or rather, there are no monsters, and nature is one whole.19 As Liceti expunged the supernatural from the world of mon-sters, Etienne expunged the unnatural. Paré’s unholy trinity—the natural, unnatural, and supernatural—was gone forever. Etienne never attained his more ambitious goal of integrat-ing his knowledge of monsters with a broad understanding ofall animal forms and evolution. Nonetheless, his work pro-pelled the examination of monsters far beyond the fantasy andprejudice that marked the writings of his predecessors. As a consequence of Etienne’s efforts, by the end of thenineteenth century when George Gould and Walter Pylepublished their comprehensive examination of teratologi-cal phenomena, Anomalies and Curiosities of Medicine, the scienceof teratology had come into its own. Their photographs andprecise illustrations can be shocking to a modern reader in away that Paré’s cartoonish images cannot. Thus, whereas Paré
Photograph of Laloo and his parasitic twin, a real-world example of a man “from whose belly another man issued.”described a man “from whose belly another man issued” withan accompanying sketch, Gould and Pyle offered a vivid pho-tograph of a normal-sized young man named Laloo, dressed inthe costume of a circus performer. Dangling in front of Laloois the torso of his child-sized twin, similarly dressed, his headseemingly stuck inside Laloo’s belly. Like a puppeteer, Lalooholds his brother at the wrists.20 Such “parasitic monsters” are so horrifying, so marvelous,that they do not seem real; but they are. So are the many otherbizarre images that ﬁll Gould and Pyle’s book: an infant with a
A PARLIAMENT OF MONSTERS s 29second partial head, a child with three heads, men with doublepenises, individuals with both male and female genitalia, womenwith beards, children without limbs, “sirens” (children whoselower extremities are completely fused, giving a mermaid-likeappearance), and individuals with double hands, hands withextra ﬁngers, feet with extra toes, or an outgrowth from thebase of the spine that resembles a stumpy tail. There is evena woodcut depicting a seated mother nursing an infant at herbreast as a standing child sucks on an auxiliary nipple locatedon her thigh.21 What do we possibly gain from such collections of unset-tling images, published for all to see and, perhaps, even ridicule?We gain perspective. We see that nature is imperfect, and withthis simple insight we illuminate our past, our present, andour future. Indeed, Gould and Pyle saw the value of theirvolume in exactly those terms. By examining monstrosities,they wrote, we seem to catch forbidden sight of the secret work-room of Nature, and drag out into the light the evidences of her clumsiness, and proofs of her lapses of skill,—evidences and proofs, moreover, that tell us much of the methods and means used by the vital artisan of Life,—the loom, and even the silent weaver at work upon the mysterious garment of corporeality.22 Around the same time that Gould and Pyle wrote thosewords, a young biologist named William Bateson was like-wise promoting monstrosities. But Bateson went further than
30 S FREAKS OF NATUREGould and Pyle and positioned monstrosities within an evolu-tionary scheme. His efforts, however, would alienate him andhis perspective from mainstream biology for many decades. D E V E LO PMENT EV O LVIN GIt is noteworthy that in The Origin of Species, published in 1859,Charles Darwin looked to the embryo for evidence to supporthis theory of evolution.23 So too did his zealous and somewhatsubversive supporter, Thomas Henry Huxley. A man whowelcomed intellectual combat, Huxley published his Evidenceas to Man’s Place in Nature four years after Darwin publishedThe Origin. In this slim book Huxley addressed head-on theissue of human evolution that Darwin dodged until 1871, withThe Descent of Man. “The question of questions for mankind,”Huxley wrote, “the problem which underlies all others, andis more deeply interesting than any other—is the ascertain-ment of the place which Man occupies in nature and of hisrelations to the universe of things.”24 Just three pages afterwriting those words, Huxley begins his discussion of embry-onic development. Huxley, like Darwin and many others,25 noted that theembryos of closely related species appear more similar than dothe embryos of distantly related species, and that differencesbetween embryos become increasingly apparent as developmentproceeds. In Huxley’s words,
A PARLIAMENT OF MONSTERS s 31 the more closely any animals resemble one another in adult structure, the longer and the more intimately do their embryos resemble one another: so that, for example, the embryos . . . of a Dog and of a Cat remain like one another for a far longer period than do those of a Dog and a Bird; or of a Dog and an Opossum; or even than those of a Dog and a Monkey.26 If embryos are nearly identical at the earliest stages ofdevelopment and only diverge at later stages, then it wouldfollow that evolution proceeds by accumulating new featuresonly at the end of embryonic development. This process, akinto adding new cars to the end of an ever-elongating train, iscalled terminal addition. Twentieth-century embryologists cameto recognize that terminal addition is not the sole develop-mental mechanism underlying evolutionary change.27 Forexample, Walter Garstang saw that a “house is not a cottagewith an extra storey on the top. A house represents a highergrade in the evolution of a residence, but the whole buildingis altered—foundations, timbers, and roof—even if the bricksare the same.”28 Today, more detailed embryological observa-tions are buttressing the notion that the earliest embryonicforms can foreshadow novel, species-typical characteristics inadults.29 Thus, modiﬁcations to embryos at any stage of devel-opment, not just later ones, can effect evolutionary changesin adult characteristics.30 But for Darwin, terminal additionwas the essential mechanism of adaptation and evolutionarychange.31
32 S FREAKS OF NATURE Moreover, in The Origin, Darwin discusses how the breedersof dogs, horses, and other domesticated animals—breederswhom he often consulted for insight and inspiration32—mate their animals based solely on characteristics or traits thatare evident in adults. Speciﬁcally, Darwin emphasizes howthese breeders, when judging their animals, are “indifferentwhether the desired qualities are acquired earlier or later in life,if the full-grown animal possesses them.”33 In other words, forthese breeders it is the product that matters, not the process. Itis the destination, not the journey. But what if the journey does matter? What if the devel-oping embryo is more than a mere intermediary in the trans-mission of adult forms from one generation to the next? Theapproach adopted by Darwin’s breeders was a bit like lookingat a list of World Series champions for insight into the gameof baseball. Each entry on the list records that year’s champion,but the details that connect champions from year to year—from spring training to opening day through the regular seasonand into the playoffs—are missing. It is history without thedrama. For anyone interested in the drama, this approach alonewould not do. One such person was William Bateson, apioneering geneticist who was convinced that the embryo hasmuch to teach us about an animal’s history, construction, andevolutionary potential.34 Born in 1861, Bateson was in his mid-thirties when he enteredinto a dispute with Darwin’s successors concerning continuity
A PARLIAMENT OF MONSTERS s 33and discontinuity among species. The Darwinians, like Darwinhimself, considered the concept of a species a mere conveniencefor characterizing the natural world. Accordingly, although spe-cies appear as discontinuous entities, the Darwinians assumeda hidden continuity—just as a single iceberg can have separatepeaks piercing the ocean surface. In contrast, Bateson believedthat species are as they appear to be Separate. Discontinuous.For Bateson, horses and humans, caterpillars and crickets,salmon and swordﬁsh, and eagles and egrets are truly, not justseemingly, separate. Thus, the notion of a species was far froma mere convenience for Bateson, but rather a foundation uponwhich a science of biological form and development could bebuilt. The Darwinian conception of evolution, then, begins witha group or population of animals in which each individual isa variation on a theme. Importantly, the observed variation isincremental and randomly generated, produced without anyconstraints imposed from within the animal. Thus, the drivingforce of evolutionary change—natural selection—has to be anexternal one. But Bateson sensed that not all variation is equally possi-ble—that developmental factors internal to the organism constrainor bias the range of forms that nature produces.35 Rather thanview natural selection as the engine of evolution, Batesonplaced his bet on variation. Indeed, in his Materials for the Study ofVariation, Treated with Especial Regard to Discontinuity in the Origin ofSpecies, published in 1894, Bateson called variation “the essential
34 S FREAKS OF NATUREphenomenon of Evolution.”36 For him, variation and disconti-nuity go hand in hand: The ﬁrst question which the Study of Variation may be expected to answer, relates to the origin of that Discontinuity of which Species is the objective expression. Such Discontinuity is not in the environment; may it not, then, be in the living thing itself? 37 For Bateson, odd, irregular, and atypical animals reveal thediscontinuity that he wished to expose. Such monsters representbiological forms uncontaminated by the demands of naturalselection, providing unfettered access to the internal rules andmechanisms of development. Moreover, as Bateson documentedin Materials, monsters were hardly the rare occurrences that manyimagined. Bateson’s nearly 600-page book overflows with oddities:a fly’s antenna that ends in a foot; a man with an extra setof nipples; a human hand with a double thumb. The vastmajority of his observations highlight subtle, but discontin-uous variations in the expression of an animal’s basic bodyplan. Bateson recorded variations in the segments of earth-worms, the vertebrae of snakes, and the ribs of humans. Heexamined teeth, fingers, and toes; wings and scales. Indeed, inhis quest for the rules of growth and variation, he examinedany anatomical feature that extends, segments, branches, ordivides.
A PARLIAMENT OF MONSTERS s 35 The discontinuous character of monsters, Bateson believed,violated the smooth continuity that Darwin had embraced (butHuxley had not 38 ). Darwin himself explicitly considered andthen rejected any role for monsters in his evolutionary scheme.39For him, they were “mere monstrosities”—abrupt accidentsthat might emerge under the watchful gaze of breeders, but notadaptive variations produced and propagated and then sustainedin response to conditions in the natural environment.40 Continuity became a core principle of twentieth-centuryDarwinism. So much so that when the geneticist RichardGoldschmidt, echoing Etienne Geoffrey Saint-Hilaire beforehim, asserted in 1940 that spanning the “bridgeless gap” thatseparates species requires “a completely new anatomical con-struction” and that this construction can arise “in one step”—he infamously dubbed such creatures “hopeful monsters”—hewas viliﬁed.41 The Darwinians considered monsters, whatevertheir form and origin, the embodiment of discontinuity, and sothey were not to be tolerated. Monsters were to have no privi-leged place in a continuous world.42 Nonetheless, Bateson’s observations revealed discontinui-ties in the developmental assembly of body parts that con-tradicted the Darwinian expectation of continuous variation.Then, upon the rediscovery in 1900 of Gregor Mendel’s experi-ments, originally conducted some thirty years earlier, on thegenetic transmission of characteristics across generations,Bateson hastily recruited Mendel’s ﬁndings to support his
36 S FREAKS OF NATUREnotion of discontinuous evolutionary change. With that, theseeds were sown for a bitter dispute43 between Bateson, consid-ered by many a stubborn man who enjoyed controversy, and agroup of mathematically oriented Darwinians, who themselveswere hardly paragons of ﬂexibility. (One of them describedevolution as a problem with solutions that “are in the ﬁrstplace statistical, and in the second place statistical, and onlyin the third place biological.”)44 The ensuing clashes of ide-ology and personality would not subside until it was demon-strated that Mendelism was not, as Bateson and others hadsupposed, incompatible with Darwinism. That compatibilitygained further traction when in 1930, four years after Bateson’sdeath, the statistician and geneticist R. A. Fisher publishedThe Genetical Theory of Natural Selection, merging Mendelian genet-ics with Darwinian natural selection. With that, the ModernSynthesis—with its emphasis on evolution as a process ofslow, incremental changes in the genetic constitution of con-tinuously varying species—was born. There was much irony in this turn of events. Bateson wouldhave been dismayed to witness the incorporation of his ﬁeld,genetics, into a worldview that he so fervently opposed. But justas troubling was the omission of development from the ModernSynthesis. This omission rested in part upon the “rupture” thatMendelism created between genetic inheritance and develop-mental mechanism.45 Also, the commitment of the founders ofthe Modern Synthesis to continuity and random genetic varia-tion convinced them that development could be safely ignored.
A PARLIAMENT OF MONSTERS s 37Goldschmidt and others criticized the Modern Synthesis for itsinattention to development,46 but such criticisms were largelydisregarded. After all, the Modern Synthesis “was not so muchwrong as it was incomplete.”47 Then, toward the end of the twentieth century, Bateson’swork suddenly became relevant again. The anomalies that hehad so carefully described in Materials for the Study of Variation werebeing produced in the laboratory by manipulating a small classof genetic components. Moreover, these components appearedto help regulate the development of animal appendages andbody segments across a surprisingly diverse array of species—indeed, in every species studied thus far, including crustaceans,centipedes, mice, and humans. Without knowing it, Bateson had laid the foundation for arevolutionary rethinking of the molecular basis of evolutionarychange. With this new thinking came a new ﬁeld—christenedevolutionary developmental biology, or Evo Devo.48 Afterdecades of exile, development and discontinuity were welcomedback into the evolutionary fold. M O R E T HAN MU T ANT SDespite its many successes, Evo Devo continues an unfortu-nate tradition of scrutinizing development primarily througha genetic lens. But if development is, as Evo Devo enthusiastSean Carroll states, “the process that transforms an egg into
38 S FREAKS OF NATUREa growing embryo and eventually an adult form,”49 then notheory of development can afford to neglect any factor thatinﬂuences that process. Unfortunately, one of the legacies ofa century of gene-focused thinking is a narrowed vision ofhow development actually happens—how at every step thetransformation of an egg into an adult involves local molec-ular events involving genes, proteins, and other molecules, aswell as often-neglected factors such as temperature, gravity,and oxygen. Consider the seemingly miraculous transformation of a mag-got into a ﬂy or a tadpole into a frog. Most of us are familiarwith the end points, but not the moment-to-moment processesthat link them. These processes are the stuff of development, butare so complex that genes alone are often invoked to simplifyand explain them to the exclusion of other, no less real but per-haps less easily manipulated factors that just as critically guideand shape the developmental process.50 If you radically changethe incubation temperature of a duck embryo, for example, youget duck soup. The overwhelming success of genetic research over the lastﬁfty years has delayed widespread acceptance of a biologi-cally realistic approach to understanding development. Thus,it should come as no surprise that Paré’s monsters are today’smutants. Indeed, in Mutants: On Genetic Variety and the HumanBody, an otherwise elegant, informative, and humane bookpublished in 2003, Armand Marie Leroi focuses primarily on
A PARLIAMENT OF MONSTERS s 39freaks as genetic anomalies. Central to Leroi’s perspective is themisguided notion that genes are entities with the power todesign and control, or that they contain the blueprint fromwhich an animal is built. In fact, on the very ﬁrst page ofMutants, Leroi clearly states this still-popular view: “Our bod-ies—I hesitate to add our minds—are the products of ourgenes. At least our genes contain the information, the instruc-tion manual, that allows the cells of an embryo to make thevarious parts of our bodies.”51 As one developmental biologist has noted,52 the metaphori-cal conception of DNA as a program, recipe, or blueprint fordevelopment has “an admirable sharpness and punch” that ishard to resist. But if we do not resist it, we can too easily ﬁndourselves on that slippery slope from literary metaphor to sup-posed fact. Instead, we should recognize DNA for what it is: amolecule that helps provide the raw materials for development.Only with that recognition can we ﬁnally embrace a biologicallyrealistic view in which DNA—contrary to the awesome powerso often ascribed to it—is seen as one among many contribu-tors to a complex and highly interactive system. Of course, genetic mutations help explain many humandevelopmental anomalies. But the intense spotlight that wecontinue to focus upon genes hides a deeper reality about devel-opmental anomalies that, when acknowledged and appreciated,leads us to a richer and more comprehensive understanding ofbiological form and behavior.
40 S FREAKS OF NATURE M O N ST ER S AT T HE T ABLEEvo Devo is but one response to the limitations of the ModernSynthesis. The reintegration of developmental and evolutionarybiology also occurred through the work of such scientists asthe late Stephen Jay Gould, who in 1977 published Ontogeny andPhylogeny, an ambitious attempt to explain how development ofan individual organism—ontogeny—is modiﬁed to alter the evo-lutionary relationships among species—phylogeny. Gould’s booktriggered a resurgence of interest in this problem. For one youngscientist, Pere Alberch, the book was particularly life changing. Charming, outrageous, irreverent—an enfant terrible accord-ing to one former student53—Pere Alberch dedicated his careerto synthesizing development and evolution. Born in Spain in1954 and educated in the United States, he was a professor atHarvard University before he was denied tenure and forced toleave in 1989. He died in Spain from heart failure nine yearslater at the age of 43. Of the many wonderful papers that Alberch wrote onestands out for its creativity and fresh perspective. Written in1989, “The Logic of Monsters” is a gem that sparkles withthe passion of a true believer. In this paper, Alberch reevalu-ated Darwinism’s central commitment to continuous variationand the power of natural selection, if given sufﬁcient time, toproduce near-inﬁnite variety. In a plea for balance, Alberchhighlighted the inherent rules that shape and guide, but also
A PARLIAMENT OF MONSTERS s 41constrain what is possible during the course of development.To bring his argument home, he emphasized the insight to begained by considering biological forms in their purest sense—even those monstrous forms that plainly exist and that just asplainly fail in the evolutionary struggle for survival. For Alberch, development is not a river of genetic infor-mation ﬂowing inexorably downstream toward the creationof biological form, but rather many rivers, tributaries, andeddies—a turbulent, cyclical process involving gene regula-tion and protein synthesis. But these complex processes donot produce inﬁnite possibility because buried within themare pattern-generating “rules of development” that “deﬁne therealm of possible variation and place limits on the process ofadaptation.”54 Alberch believed that monsters are ideal subjectsfor investigating these inherent rules and patterns. They areambassadors of pure form and thus deserve a seat at theevolutionary table. So, like Bateson, Alberch distinguished between the externalforce of natural selection and the internal dynamics of develop-ment.55 He contrasted the evolutionary lineage of a species withthe developmental history of an individual; the transmissionof form across generations with the regenesis of form withineach generation; the unconstrained with the constrained; thepast with the here-and-now. But unlike Bateson, who may have tipped the scale toofar in the direction of internal factors and extreme variation,Alberch sought balance. He argued that the animal forms that
42 S FREAKS OF NATUREwe see around us must result from a combination of internalfactors producing a broad range of discrete—not continuous—variations,56 and external factors selecting among them. Butbecause gene-centered, population-level thinking—enshrinedby the Modern Synthesis—invariably escorts us toward theexternalist perspective, Alberch appealed for renewed emphasison the study of form from the internalist perspective. To putthis appeal in the starkest terms possible, he thrust monstersforward as a good starting point towards such a goal; they represent forms which lack adaptive function while preserving struc- tural order. There is an internal logic to the genesis and transformation of such morphologies [different forms and structures of living organisms] and in that logic we may learn about the constraints on the normal.57 Alberch was writing when the pioneering experiments thatwould establish the ﬁeld of Evo Devo were fresh and theirimplications were only beginning to be appreciated. He graspedthe signiﬁcance of identifying a small, ﬁnite number of genesthat contribute to the construction of similar body parts acrossa wide array of species. Many Evo Devo enthusiasts see suchgenetic insights as further evidence of the primacy of genes.In contrast, Alberch saw these new ﬁndings as support for hisbelief in internal constraint, in a relatively small number of cel-lular combinations and operations available to the developingorganism.
A PARLIAMENT OF MONSTERS s 43 Thus, when faced with a novel animal form—for example,a ﬂy with an extra pair of wings—Alberch did not immedi-ately imagine a novel trait produced by some magical mutation.Rather, he saw a system that had been modiﬁed to produce anovel form. Consequently, he understood the need to deter-mine how all of the components of the system—genetic andextra-genetic—interact to produce both typical and novelforms. Ultimately, appreciating the intimate connection betweendevelopment and evolution requires a perspective that dif-fers from that associated with traditional Darwinism. RecallDarwin’s description of the indifference of animal breedersto “whether the desired qualities are acquired earlier or laterin life.” But evolution is not indifferent. On the contrary, thenotion that selection—whether natural or artiﬁcial—acts onlyto preserve individual anatomical traits is misleading. Forexample, when a farmer breeds dogs to herd or cows to pro-duce milk, he is selecting for much more than just herding andmilk production. In particular, what is being preserved acrossgenerations is the developmental means58 to produce the desiredoutcome, as well as all of the other features that come along forthe ride.59 Scientists and breeders may often ignore such non-obvious and unpredictable side effects of selection, but thatdoes not diminish their signiﬁcance for an individual and itsdescendants. The focus on developmental process rather than geneticallypreordained product is the hallmark of the perspective known
44 S FREAKS OF NATUREas epigenetics.60 Epigenetics—and the foundational concept ofepigenesis, which can be traced back to Aristotle—embodies theinteractive nature of development. When Conrad Waddingtoncoined the modern term in the 1940s,61 he conjured the imageof a sloped terrain of hills and valleys, upon which a rollingball—representing the development of an embryo—coursesdown one path or another.62 Waddington went further with his metaphor to suggestthat the landscape itself was like a piece of fabric draped overa complex interconnected system of ropes anchored to pegs.Tension on the ropes produced the valleys in the landscape’sfabric above, and, as he imagined must be the case with anygenetic system, a change in the tension in one location wouldhave cascading inﬂuences on the shape of the entire landscape.Change this epigenetic landscape and development will course downa different path. Though Waddington’s visual image would eventuallyprove a powerful one, it could never compete with the moreeasily grasped “sound bites” that geneticists were offering.Epigenesis cannot be reduced to a sound bite. Indeed, after somany decades of the steady drumbeat of genetics, epigenesis cansound too nuanced, perhaps even mystical. But it is neither. Itis the way things actually are—elaborate and complex, tortuousand convoluted. The epigenetic perspective is one among several core prin-ciples that deﬁne a broad conceptual scheme now referred to asDevelopmental Systems Theory (DST).63 The proponents of DST
A PARLIAMENT OF MONSTERS s 45seek to replace the simplistic single-cause, gene-centered think-ing that is so prominent today. They note how genes have beenascribed the dual role of being the designer of development andthe sole means by which design is inherited by members of thenext generation. This double duty foisted onto genes is a doublemistake: Having placed so much control into the hands of meremolecules, we must now work hard to distribute that controlmore equitably. DST aims for this equitable distribution by emphasizinghow genes are only one part of a complex, interacting, devel-opmental dynamic. Moreover, genes are not the sole means ofinheritance. On the contrary, the list of nongenetic mechanisms ofinheritance is now quite long, and it includes inherited featuresof the external environment—including gravity and oxygen,jungles and oceans, nests and burrows, and even language—aswell as a variety of inherited nongenetic molecular processesthat inﬂuence gene expression and other developmental events.This notion—that the environment consistently and reliablyshapes development across generations—can no longer be cred-ibly denied. Still, many remain skeptical, leading one prominentevolutionary thinker to rank this skepticism “among the oddestblind spots of biological thought.”64 When considered in its entirety, DST offers a balanced andrealistic perspective of development that is sorely needed today.It views development as a process in which all componentsparticipate in the moment-to-moment construction of the indi-vidual, generation after generation, genesis and regenesis.
46 S FREAKS OF NATURE Consistent with DST, Alberch criticized the notion thatinformation ﬂows from the genes like water from a faucet.Instead, he saw nested cycles of interactions—loops within loopswithin loops—that regulate the expression of genes both withineach individual cell and among all the cells of the body. Thus,gene expression results in the production of proteins, proteinsparticipate in the physico-chemical interactions within cells, andthese interactions ultimately result in the production of new tis-sue. In turn, the physical orientation of tissues modulates thenext round of gene expression. And round and round it goes. H A RD AND SO FT P AR T SFreaks sometimes arise through human intervention, both realand imagined. Prehistoric cave drawings depicting human–animal hybrids testify to an ancient fascination with impossiblecreatures. In 1894, H. G. Wells manipulated this fascinationto great effect in his darkly disturbing novel, The Island ofDr. Moreau. In his story, Wells introduces us to a physician,working secretly in a laboratory on a secluded island, brut-ishly attempting to “humanize animals” through surgical inter-cession—“animals carven and wrought into new shapes.”65Moreau’s attempted demonstration of the “plasticity of livingforms”66 managed only to produce “grotesque caricatures ofhumanity.”67 Some people feel that our current obsession withplastic surgery for cosmetic purposes—itself emblematic of the
A PARLIAMENT OF MONSTERS s 47human tendency to tinker with what nature provides, in pursuitof beauty or perfection or simply to ﬁll in nature’s gaps—produces similarly grotesque results. If, through Moreau, Wells made an error, it was in not fullycomprehending the difﬁculty of transforming animals oncethey have reached adulthood. Surgical intervention in adultscannot guarantee the full integration of parts that develop-ment accomplishes so effortlessly. The same can be said forother interventions. For example, steroids may enhance athleticperformance, but their harmful side effects betray an inter-dependent system whose balance has been upset. In contrast,as embryologists know well (and as we will see repeatedlythroughout this book), tinkering with an embryo can result inbizarre animals whose parts nonetheless develop and functionin an integrative manner.68 Throughout the world, members of diverse societies—inpursuit of their own idiosyncratic ideals of beauty—havecome to understand which features of human anatomy can andcannot easily be manipulated.69 On the one hand, the body’ssoft parts—lips and ear lobes, for example—can be radicallydistorted, almost at will. Consider the enormous plates thatwomen of the Surma and Bumi tribes of Ethiopia and Sudanare able to insert into their lower or upper lips. Such fantasticexaggeration of the lips, involving soft tissue alone, can be pro-duced at any age. On the other hand, manipulating the hard parts of the body—that is, bone—requires early intervention, ideally during periods
48 S FREAKS OF NATUREof rapid growth. For example, archeologists have documentedancient and worldwide cultural practices aimed at deformingthe skull during early infancy. Many techniques have been used:In pre-Columbian Peru, wooden boards were strapped to theheads of newborns to produce a “tower skull.” In the PaciﬁcNorthwest, members of the Chinook tribe would bind a supineinfant to a board and then tie another board over its head at a25-degree angle. After many months in this position, the infantwould sport a pronounced sloping skull that was a mark of dis-tinction in Chinook society. Of course, the skull has not beenthe only hard part targeted for change: For about 1500 years inChina, young girls were often required to bind their feet to pro-duce a stumpy form for the inexplicable pleasure of men. In all of these cases, societies have adopted methods thatmodify the mechanical forces that normally shape bone devel-opment to produce almost any desired feature. Thus, just as thegrowing brain is an internal force that inﬂuences the size andshape of the skull, outside forces are no less able to redirect thegrowth of the skull (and, as a consequence, the shape of theunderlying brain). Similarly, the mechanical forces of walkingthroughout infancy help to shape the bones of the feet, just asthose bones are shaped by foot binding. Bone growth is not pre-determined; rather, bones are sculpted as the internal dynamicsof growth play out within the context of real-world experience.Similar processes continue to shape and reshape bones through-out our lives—after a break, for example—but again, not asdramatically as when we are young.
A PARLIAMENT OF MONSTERS s 49 Like bone, our brain and the behavior it helps produce areshaped by experience. In fact, as a learning organ, the brainspecializes in adaptability. In the jargon of the ﬁeld, we saythat it exhibits plasticity. But there is more to adaptive behaviorthan the plasticity of the brain. In fact, behavior is shaped andmolded by the hard, anatomical realities of the growing bodyand the concrete physical world in which that body develops. To illustrate this point, imagine lying in bed on a hot sum-mer night. You have no air conditioning and your only sourceof relief is the ceiling fan. You throw off the covers to help youcool down, but still you feel hot and sweaty. If you are like mostpeople, you sprawl out on the bed, legs and arms outstretched,as you maximize the amount of skin surface from which to losethe heat. Now imagine that it is a dreadfully cold winter nightand your heating system has failed, so you are under the covers,struggling to stay warm. You curl up in a ball, your knees closeto your chest, your arms held tightly to your torso. Indeed, thevery thought of stretching out gives you a chill. How do we know which postural adjustments will bringmaximal relief during those hot summer days and frigid winternights? You might wonder whether this knowledge is hard-wired in our brain, but there really is no need to hardwire thatwhich is learned quickly and efﬁciently through experience.Thus, as our bodies grow, as we fatten up and slim down, andas we experience a wide range of temperatures, we learn howbest to maintain thermal comfort. We buy special clothes—Bermuda shorts or a thick woolen parka. We cool or heat our
50 S FREAKS OF NATUREhome. We drink iced or hot tea. We learn to adjust our posture.The ideal positioning of our torso and limbs may be slightlydifferent for each of us, but we quickly learn that sprawlingworks in the heat and curling up works in the cold. We learnfor ourselves and we learn similar things. For these reasons, ourbehavioral responses to hot and cold conditions are both per-sonal and universal. Consider a second example, one that is admittedly bizarre.Consider the fact that when humans urinate, females typicallysquat and males typically stand. Human cultures recognizethis universal feature of human behavior and reinforce it in thedesign of our restrooms: urinals for men in public buildingsand liftable toilet seats for them everywhere else. Such a uni-versally expressed sex-speciﬁc behavior suggests the presence ofan instinct, one that might even inspire the search for a geneticcause. But such a search would be pointless. Of course, it is obvious that the chromosomes associatedwith being male and female—XY and XX—would be associ-ated with standing or squatting to urinate. But the more impor-tant point is that no specialized behavior-altering genes arenecessary. Why? Because the standard urinating position ofeach gender simply reﬂects the fact that males have an external,tubular, urination apparatus—a penis—and females do not;and because females (and males) accumulate similar life expe-riences with their anatomical parts, most females (and males)arrive at the same behavioral destination. Thus, females preferto squat because the alternative is the discomfort of a moistened
A PARLIAMENT OF MONSTERS s 51leg. For their part, males prefer to stand because sitting takestime and effort; in effect, males urinate while standing becausethey can. The implications of these seemingly trivial examples areboth serious and edifying because curling up, sprawling, andurinating are universally expressed behaviors that nonethelesscan be explained without appealing to “genetic hardwiring ofthe brain” or other exotic and magical forces within the animal.These examples show us how behavior—like a skull squeezedbetween two boards—can be molded under the guiding inﬂu-ence of persistent and mundane external factors. Given our world and our bodies, certain behavioral outcomesare inevitable. But any satisfactory explanation of developmentrequires a detailed understanding of the mechanisms that giverise to anatomy and behavior. To achieve such an understand-ing, we must ﬁrst accept the fact that the cycles and spirals ofdevelopment—the loops within loops within loops—precludea straightforward story of causes and effects. Too many of ourcherished concepts, nurtured in the presumption of a linear,rational, and ordered world, simply fail to adequately capturethe turmoil of development. Anomalies reﬂect that turmoil. They jar our senses, challengeour complacency, and force us to confront our preconceptions;they help us appreciate the ﬁne balance that exists between theidiosyncrasies of individual development and the vagaries ofevolutionary history; and they open a window to the nature ofdevelopment itself—to the moment-to-moment construction
52 S FREAKS OF NATUREof the bodies and behaviors of all animals, be they “freaks” or“normals.” Whether we are talking about two-headed sistersand two-legged goats, or armless wonders and limbless snakes,or disﬁgured frogs and ﬁsh that switch sex, or you and me,development is very personal.
TWO - Arresting Features Development is All about Time . . . the analysis of normal developmental processes and the experimental study of monstrous development [are] one and the same problem.” Charles Stockard (1921) 1 . . . the speeds at which the internal factors work are of great importance in development, and variations in the relative speeds of the various factors may play an important part in the relation of ontogeny to phylogeny.” Gavin de Beer (1940) 2F or one moment, many years ago, I was a great drummer—at least I felt like one. In any event, it was just a moment.I had been working for days on the most complicated beat I hadever attempted. It required each of my limbs to dance rapidlyin a temporally precise pattern that, as the beat was notated,seemed too intricate for one body with just four limbs. But onthis day I nailed it, my hands and feet punching out the rhythmas my mind, lagging slightly behind, observed and enjoyed the 53
54 S FREAKS OF NATUREgoings-on as much as a second listener might have. From thisrespectful distance, my mind started to intrude, now trying tocontrol—not just observe—the individual movements of eachof my limbs. Suddenly everything fell apart, sticks and limbscolliding like a pile-up on the interstate. Successful drumming requires well-timed effort amongdiverse parts: ﬁnely tuned commands from the nervous systemcontrolling muscles that are connected to stiff bones by elastictendons. This mechanical system is extended to sticks grippedﬁrmly yet ﬂexibly in each hand, and to the “skin” of eachdrum. Every strike of the stick against the drumhead producesa reaction that inﬂuences the timing of the next strike. Hitoff center or too hard and the stick bounces off in a directionor with a speed that’s unexpected, altering and occasionallydisrupting the timing of subsequent movements. In my case,merely focusing on my limb movements was enough to upsetthe delicate timing relationships that I had achieved throughhours of practice. Development also entails a balance among diverse partsinteracting through time. As we will now see, even subtle disrup-tions to this balance can dramatically alter the development ofthe face and head, resulting in the emergence of unexpected andeven monstrously novel structures. But it will also become clearthat these “unexpected” novelties are not randomly produced.On the contrary, as Pere Alberch observed, there is a logic tomonsters. To fully appreciate that logic, we must never neglectthe central importance of time.
ARRESTING FEATURES s 55 FACE T IME“Ever wonder where our worst nightmares come from?” So began a 2003news report announcing the discovery of the fossilized remainsof a giant and now long-extinct “one-eyed” creature on the Greekisland of Crete.3 Considered in the context of Homer’s terrify-ing description of a man-eating Cyclops in The Odyssey, writtenover 2500 years ago, the discovery suggests a possible source forHomer’s inspiration.4 But although this fossil belonged to anelephantine relative, not to a Cyclops, the news report’s allusionto a single “eye socket” implies a connection between myth andreality that is not far fetched. Consider a modern elephant’sskull, such as the one shown on the following page, with a largehole in the forehead. Of course the hole is not an eye socket.Rather it marks the location of the nasal cavity to which thetrunk connects. The true eye sockets sit inconspicuously off tothe sides. Thus, looking at this skull head-on, we see a large cen-tral hole that an ancient Greek, unfamiliar with living elephants,could easily have mistaken for the former home of a single,centrally located eye. Although compelling, the notion that mythological crea-tures emerged from human encounters with the fossils of long-extinct creatures may not be the whole story. As mentioned inChapter 1, the iconic images of the Roman gods Janus and Atlaseerily reﬂect embryological, not paleontological, forms. Thesame may be true of Homer’s Cyclops. After all, why imagine
An elephant skull. Note the large central nasal cavity. The eye sockets are barely visible off to the sides.adding ﬂesh to bone to envision a Cyclops when some infantsof humans and other animals appear in the exact form—if notsize—of Homer’s creation? Perhaps—and this is mere specu-lation—the mythical Cyclops arose by combining a mistakeninterpretation of a giant fossil skull with the unmistakablehorror of a tiny cyclopic infant. Leaving aside the origins of the mythical Cyclops, we neednot speculate about the origins of cyclopia because we alreadyknow a lot about it. For example, we know that cyclopia is theextreme form of a series of abnormalities that affect the entireface. These facial abnormalities mask equally extreme problemswith the brain. In fact, cyclopia and its associated defects areknown collectively as holoprosencephaly, a name that highlightsthe failure of the forebrain to divide into two separate halves.The incidence of holoprosencephaly may be as high as 1 in 250fetuses, but because most of them do not survive to term, only
ARRESTING FEATURES s 57about 1 in 16,000 infants are actually born with this condition.5In the most severe cases, including cyclopia, nearly all will diewithin one week.6 In the early twentieth century, the zoologist HarrisHawthorne Wilder sought to develop a conceptual frameworkto better understand cyclopia and related abnormalities. Inparticular, it impressed Wilder that “the cases usually classedas ‘monstrosities’ can be as natural and symmetrical in theirdevelopment as are normal individuals . . . .”7 But it is not soeasy to adopt Wilder’s noble perspective while gazing upona cyclopic infant. Wilder’s perspective can come only withrepeated exposure and desensitization. For example, consider the sketches on the following pagefrom one of Wilder’s papers.8 If this is your ﬁrst experience withcyclopia, you may wonder whether such creatures are any morereal than the most fanciful beasts of human imagination. At ﬁrst,you may ﬁnd that the single eye grips your attention. But overtime, you may begin to notice the empty space between eye andmouth and even perhaps that odd structure above the eye (at ﬁrst,I thought this structure was only a smudge on the page). Wouldyou, like Wilder, choose to describe these images as “natural”? Because my introduction to cyclopia came through a car-toon, I remained unconvinced that such infants actually existuntil I saw photographic proof. But although the photographsconvinced me of the reality of cyclopia, each image—of chemi-cally preserved infants staring with that single unblinking eye—only pushed me further away from the lofty perspective that
Two sketches from Wilder’s “Cosmobia” series depicting two forms of cyclopia. Note the absence of a nose in the middle of the face and the proboscis above the eye.Wilder espoused. The cartoons, on the other hand, providedmuch-needed distance such that, over time, I gradually cameto appreciate cyclopia as a biological form worthy of carefulattention. As I became accustomed to the presence of a single, centrallylocated eye and as I studied Wilder’s other sketches, one ques-tion became increasingly salient and puzzling to me. What, Iwondered, might account for the fact that some of the infantsWilder examined had noses and some did not? Today, scientists inundate us with “discoveries” of genes forevery identiﬁable trait, such as depression, thrill seeking, andjealousy. Well, within the realm of identiﬁable human traits, thenose is certainly more distinct than depression or thrill seeking.So, does its absence in a cyclopic infant imply that the “genefor the nose” has wandered off with the “gene for two eyes”?Are these two genes somehow linked, like conjoined twins? Orperhaps these two genes comprise a single fragment of DNAthat serves two facial functions. To entertain these simplistic genetic fantasies is to take oureyes off the developmental processes that truly matter. Wilder
ARRESTING FEATURES s 59revealed these processes by creating and ordering a series ofimages (not unlike a geologist conveying the erosive power ofwater using time-lapse photography). Thus, the next face inWilder’s series, presented below, now shows two eyes—close-set but nonetheless distinct—and, for the ﬁrst time, a nose. The nose’s appearance in its proper location seems almostrefreshing, as if the world has been made right again. But wheredid it come from? Glance back and forth between the varioussketches and the answer presents itself: That “thing” above thecyclopic eye is a nascent nose (a proboscis in technical jargon), itspath to the middle of the face blocked by eyes that have notgotten out of the way. In Wilder’s words, written a centuryago, “the nose, which is prevented from coming down in theusual manner through a downward growth of the fronto-nasalprocess, remains above the double eye and presents a shapesomething like a proboscis, decidedly abnormal, but character-istic of all monsters in whom there is no space between the eyecomponents.”9 Two more sketches from Wilder’s “Cosmobia” series depicting a properly located but rudimentary nose (left) and a fully formed nose (right).
60 S FREAKS OF NATURE But even the nose depicted here, having squeezed throughthe narrow space afforded by the barely separated eyes, is only“a small and narrow nose rudiment, usually with a single mediannostril.” When the eyes provide more space, as shown in theﬁnal sketch in this series, a normal nose results. We now know much more than Wilder did about how thedeveloping eyes inﬂuence the developing nose. In particular, theeyes do not begin as a single centrally located eye-ﬁeld thatthen divides and moves laterally to produce two eyes.10 Rather,the eye-ﬁelds begin as a continuous line of cells awaiting achemical trigger that suppresses activity in the eye ﬁeld’s centralregion. When this suppression occurs, the line of cells is dividedinto two separate eye-ﬁelds that can then develop further intotwo properly placed eyes. Like cars arriving at a crowded intersection, the group ofcells that will produce a nose cannot move along until the eyeﬁelds have given way. The nose cannot go around, and so itmust wait for an opening and that opening must arrive on time.Otherwise, the face will be stuck with that oddly shaped andpositioned proboscis that signiﬁes the cyclopic infant. The fact that the same cells that build a nose can so easily pro-duce a tubular proboscis reﬂects a fundamental developmentalprocess—called induction—whereby interactions between neigh-boring tissues stimulate changes in gene activity and producenew tissue. In other words, body parts arise when cells of onetype interact with neighboring cells of another type, with theinteraction producing gene activity that induces the development
Enlargement of Wilder’s sketch of a cyclopic infant to show the proboscis located above the eye (left). A young elephant (right).of the body part in question. Aquiline nose here—ungainlyproboscis over there. Does the shape of the proboscis of the cyclopic infant remindyou of the trunk of an elephant? If so, perhaps—and here I amreally speculating—elephants evolved trunks by manipulatingthe developmental interactions among the cells that produceeyes and proboscis. This speculation seems a bit less fancifulwhen we compare the fetus of a normal elephant11 with thatof a cyclopic mouse,12 as shown on the following page. Nowthe striking resemblance between their enlarged proboscises iseven more apparent. Thus, not only does the nasal cavity of anelephant resemble the bony socket for a cyclopic eye, but theﬂeshy trunk that connects to the nasal cavity also resembles thenose of a cyclopic fetus. Whereas the former resemblance maybe superﬁcial, the latter may reﬂect a deep embryological link. Although this embryological link between the proboscisesof elephants and cyclopic infants is speculative, the lesson illus-trated by Wilder’s sketches is not: The same tissue can growto be a nose or a proboscis depending upon the nature of thelocal cellular interactions. In the case of the nose, avoiding the
An African elephant fetus ﬁfty-eight days after conception (left). An embryonic mouse engineered without the sonic hedgehog gene (right); note the enlarged proboscis.development of an unsightly proboscis depends upon the timelymovement of cells from one locale to another. ——Around the same time as Homer, 7,000 miles west of Crete inTlatilco, a small village on the outskirts of present-day MexicoCity, sculptors were representing a different category of facialdisﬁgurement. Their striking creations would mesmerize thearchaeologists who unearthed them 3,000 years later. Thesesmall ceramic ﬁgurines depict gracefully rendered female forms.Most are naked, with bulging thighs, slim waists, blunted arms,and heads adorned with fancy hair-dos. Each face is fully real-ized, often giving the impression of a mask concealing the trueface underneath. A few dozen of the ﬁgurines offer much more than merestylized representations of the female form. These ﬁgurinesare typical in every respect but one: the presence of two facesoccupying the single head. Scholars have usually interpretedsuch sculptures as representations of mythological or spiritualbeings. Indeed, why would we think anything different aboutthese two-faced Neolithic ﬁgurines?