jac 30.3–4 (2010)

The Rule of Thumb

Tom Tyler

Animal superiority lies in the hand; man’s in the thumb.

—L’Apertigny

Three myths are often recounted regarding the human thumb. The firstconcerns that durable phrase “rule of thumb,” which dates back at leastto the seventeenth century, and means, roughly speaking, an approximatebut serviceable method based on experience rather than precise calcula-tion. It has been suggested that the expression derives from the traditionin British common law which permitted a husband to “chastise” his wifeso long as the switch or rod used was no thicker than his thumb. Calls havebeen made to boycott all use of the phrase on account of this distastefulderivation. In fact, there is no evidence to suggest that the phraseoriginated in domestic abuse: it does not appear in legal history, in whichuse of the thumb as any kind of standard is rare. On the other hand,however, irrespective of whether this practice was officially sanctioned bylaw, it is clear there certainly existed a popular belief that, within these“reasonable” limits, wife-beating was tolerable. Thus, although the originof the perfectly innocent phrase “rule of thumb” does not lie with violentabuse, it seems that the thumb was perceived as a de facto standard in thisregard.1

The truth of the second myth is similarly gruesome. It is generallybelieved that the “thumbs up” gesture, widely employed across Europeand elsewhere, originated in the Roman Colosseum. When a bestedgladiator lay prone, the crowd would advise the emperor on his fate eitherby showing upturned thumbs whilst crying “Mitte!” (release him!), or, withtheir thumbs turned down, pollice verso, by calling out “Iugula!” (slay

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him!). The emperor would confirm their verdict, or not, according to hiswhim. From this grisly origin, it is supposed, come our modern thumbsignals meaning “okay” and “not okay.” In fact, pollice verso does notmean a downturned thumb, but simply a turned, or moving thumb: thosewho wanted the gladiator slain presented their thumb in full sight, perhapsjabbing it in the motion of a stabbing (see Juvenal 3.36). Those who wantedto spare him, meanwhile, kept their thumbs out of sight, pollice compresso.Thus, simply showing your thumb in any way meant just one thing:“Iugula!”2 In the Colosseum, then, we find a different but no lessoppressive rule of thumb.

Finally, and it is on this third myth that I would like to dwell, we oftenhear that it is opposable thumbs that make humans the unique kind of beingthat they are. The importance of the thumb has been recognised sinceancient times. Galen tells us (1.22) that Hippocrates called it the “greatfinger” (μεγας, megas), and Aristotle was in no doubt as to its value:

One finger extends out of the side of the hand, and is short and thick,not long; for just as, if there were not a hand at all, one could notgrasp, so too one could not grasp if this finger were not growing outof the side. For it squeezes from below upwards, while the otherssqueeze from above downwards. And this must happen if it is tobind things together strongly, like a strong clamp, in order that,though one, it may be equal to many. (687b)

For the ancient Greeks, the thumb was the αντιχει (antikheir),meaning “another hand” or a “second hand.” The preposition anti meansboth equal and opposed to, the thumb’s importance deriving precisely fromthe fact that it is considered equal in strength to the other fingers, andopposes them. According to Macrobius, the thumb “always has as muchwork to do as a whole hand” (7.13.14), whilst Isidore tells us that it“opposes the other fingers with strength and power,” for which reason itis called in Latin the pollex, from pollere (to be powerful, to exertinfluence) (9.1.70). Montaigne devoted a short essay to this “masterfinger,” quoting from Martial, Horace and Juvenal, amongst others.Albinus, the eighteenth century anatomist, suggested that in the thumb thehand had been given an assistant, an additional “little hand” (290). Theanthropologist Marvin Harris has argued that, “the length and strength of

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the human thumb give us a uniquely precise grip, powerful yet delicate.This grip, almost as much a hallmark of humanity as bipedalism andbraininess, has helped to make us the supreme artisans of the animalkingdom” (28). And most recently, in September 2008, scientists huntingfor the genetic enhancers most likely to have contributed to humanevolution, seeking that is to “understand, at a molecular level, what it meansto be human,” announced that the fastest evolving noncoding sequence ofthe human genome yet identified turned out “to play a unique human-specific gene activating role in a region of the developing limb thateventually forms the junction of the wrist and thumb, and also extendspartially into the developing thumb.” The press release accompanying thearticle in Science suggested that this genomic region “may have contrib-uted to the evolution of the uniquely opposable human thumb.”3 It is thesemarvellous, uniquely opposable thumbs, we are told, which permit humansto engage in all those dextrous, significant activities that have made themveritable masters of the animal kingdom. As we will see, accounts of theimportance of opposable thumbs suggest a rule of thumb all their own.

Paeans to the Perfect Pentadactyl Hand

In the pages that follow, I wish to consider this proud, perhaps evenexultant characterisation, which Stanley Cavell has called “the romanceof the hand and its apposable thumb” (41–42). In particular, I want toexamine the claim, often made in both popular and professional writings,that opposable thumbs, and the hands they make possible, are unique tohumanity, an exceptional endowment and the marker of a distinctive placewithin the natural world. Are opposable thumbs the key to the hand? Is thethumb and the grip it provides really a “hallmark of humanity”? Is it thumbs,those “little hands,” that make human hands true hands, the only perfectand complete hands? And is there such a thing as an inhuman hand? Ananimal thumb? What would such an inhuman member look like? To beginto answer these questions, I would like to start with the work of anineteenth century writer, and to explore what his work can tell us aboutcontemporary understandings of the hand and thumb.

In 1833, the surgeon, anatomist and natural theologian Charles Bellpublished the fourth of the Bridgewater Treatises, a series of eight texts

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devoted to the task of demonstrating the “Power, Wisdom, and Goodnessof God, as manifested in the Creation.” Bell’s treatise was entitled TheHand: Its Mechanism and Vital Endowments as Evincing Design. Thehand, Bell argued, is the organ that corresponds most remarkably withman’s capacities (2). In it, a large number of properties that are sharedwith the brutes are brought to perfection. The combination of strength withvaried, extensive and rapid motion; the form, relations, and sensibility ofthe fingers and thumb which permit unprecedented holding, pulling,spinning, weaving and constructing: all these correspond to the superiormental capacities with which man has been endowed, allowing him tocarry out whatever he conceives (252–53).

We ought to define the Hand as belonging exclusively to Man—corresponding in its sensibility and motion to the endowments ofhis Mind, and especially to that ingenuity which, through means ofit, converts the being who is weakest in natural defence, to be theruler over animate and inanimate nature. (18)

Man is superior to the brutes with regard to his mind, allowing him to existin every climate and to survive on every variety of nutriment, but it is thehand that makes all this possible and which, “by its correspondence withthe intellect,” allows him “universal dominion” (41). Bell refers time andagain to the perfection of the human hand, a perfection that speakssimultaneously of the benevolence of a divine Author and the preeminenceof the recipient of that design (15, 252, and passim).

Is the hand unique to man? There are certainly creatures, Bell admits,who possess appendages that look or function, more or less, like hands,some of which come equipped with what seem, to a greater or less extent,like thumbs. The remarkable tail of the spider monkey “answers all thepurposes of the hand” (19), and a “vulgar admiration is excited by seeingthe spider-monkey pick up a straw, or a piece of wood, with its tail” (15).This, of course, is not a hand, however, and further, when we look at theend of the monkey’s arm we find the “thumb” to be so small that it hasalmost disappeared (90). The elephant possesses “an instrument, like ahand, in the proboscis,—to minister to the mouth, to grasp the herbage, andlift it to its lips” (332). This trunk, although called manus in Latin, is surelynot a hand, however. Bell defended the supposedly “faulty composition”

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of the sloth, and even noted that he climbed “hand over head,” but he mostoften refers to those three-fingered appendages as claws (30). Of thelight-boned bats, the hand-wings (Chiroptera), Bell notes that “thephalanges or the rows of bones of the fingers, are elongated so as hardlyto be recognised” (74–75). But, setting aside Bell’s confident assertionthat the Hand should be defined as exclusively human, what of those othercreatures whose limbs’ ends are more clearly comparable to human handsthan the claws and wings of sloth and bat? What of the panda’s dextrouspaw, complete with extended, gripping thumb.4 What of those species offrog who possess not just five but six fingers to a limb? What ofchameleons, who have two opposable digits on each hand? Is the tale toldof uniquely human opposable thumbs another myth, another suspectattempt to rule by thumb?

The anatomist and anthropologist Frederic Wood Jones distrustedpaeans to the hand, both old and new:

It would be a difficult matter to find the author who, writing of thehuman forearm and the human hand, has not seen in them the veryhighest and most perfect development of the fore-limb foundanywhere in the animal kingdom. It has long been customary tolavish praise upon this culmination of human perfections, or climaxof evolutionary advances, as writers of different periods havejudged it. (Arboreal Man 43)

Jones observed that changes in these “almost inexhaustible eulogies” after1859, the date of publication of Darwin’s Origin of Species, were largelysuperficial. The hand and forearm came to be regarded “not as awonderful and specially designed structure, but as the perfected productsof accumulated ages of evolution—the last thing in animal developmentand specialization” (45). Here, in miniature, was the classic misunder-standing of Darwinian theory: evolution as progress. Humanity is no longerspecially created, but instead specially evolved, the culmination and acmeof evolutionary processes (45–46). Man, now sitting at the very top of thegreat chain of being, gazes down first at the horses, dogs and his fellowmammals, and then on to the lizards, fish, and assorted series of “lower”creatures. “A foolish argument,” says Jones, “may be permitted in dealingwith a folly” (45). We should imagine, he suggests, an equine anatomist

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producing a Bridgewater Treatise on The Construction of the Hoof ofthe Horse, followed shortly after by a Descent of the Horse. The humanforelimb would undoubtedly suffer badly, and these hypothetical workswould thus, he suggests, be a most healthy tonic for human anatomists andphilosophers alike.

The hand, far from being a specialized highpoint of the evolutionaryprocess, is in fact a rather archaic appendage. Aristotle drew specialattention to the fact that the five fingers are separate and distinct (687b),but as Jones demonstrates, pentadactylism is the “hallmark of primitive-ness” (Principles of Anatomy 22). These five fingers collectively point,he shows, toward “something extraordinarily primitive about the hand thathas been preserved and passed on to man” (Arboreal Man 20).5 Thepentadactyl limb is an ancient attachment, predating even mammalian life.Separate and distinct digits belong to numerous members of the massivesuperclass Tetrapoda, the four-limbed vertebrates, which includes am-phibians, reptiles, birds and mammals. It was from the very earliesttetrapods, the so-called “four-footed fish” who would go on to dragthemselves into the inviting new shallows and wetlands of the lateDevonian, 365 million years ago, that we modern tetrapods inherit ourflexible fingers. The origins of the five fingered human hand reach backa long way indeed.

The division of the hand is certainly what makes it so flexible, soversatile, but that does not make it either unique to humanity or anevolutionary highpoint. In fact, the creatures whom we might moredeservingly describe as “advanced” are those that have evolved beyondthe ancient, pentadactyl condition. This move away from the “primitive,”6

toward increasing specialisation, manifests as a diminution in the numberof digits. The most ancient of the Devonian tetrapods were Acanthostegaand Ichthyostega. As Stephen Jay Gould explains in his essay “EightLittle Piggies,” research published in the 1990s demonstrated that mem-bers of these two genera, though still confined entirely to water, had notfive, but six, seven or even eight digits on each limb.7 Fingers have actuallybeen lost in the intervening millennia, as species specialise. It is amongstthe ungulates, the hoofed beasts, that this “digital reduction” has been mostfully accomplished (Jones, Principles of Anatomy 21). Bell himselfdiscusses that “most perfect piece of mechanism,” the horse’s hoof, so

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well suited to the extensive plains and steppes where these great creaturesoriginally roamed (Bell 94–98). Considering the remarkable combinationof strength and elasticity in this fine apparatus, Bell observes that there isjust a single digit enclosed in the horse’s bony hoof. It is this specializationthat allows the horse to run such great distances at such high speed. But,as Jones points out, the unspecialised human fore-limb “is far more like thatof a tortoise than it is like that of a horse” (Arboreal Man 46). If theauthors of those two hypothetical texts had sought to derive their highlyspecialized limbs from those of a more primitive form, they would, “withfar more justice” than humans, have regarded their race as the last effortin evolutionary chronology (45).8

Between Thumb-Catching and Taxonomic Nominalism

Horses’ hooves are clearly not hands. So just how many fingers does ahand have to lose before it becomes some other appendage? Is it just thethumb, the digit which, as in the case of Bell’s spider monkey, is usuallythe first to go?9 What of those, like the six-fingered frogs, and polydacty-lous Acanthostega and Ichthyostega, who have more than five digits?Can a hand have too many fingers? We return to the question: what makesa hand? Wittgenstein provided a playful image with which to illustrate thestate of affairs, so often encountered by philosophers, wherein they seemto know what it is they wish to discuss, but manage to perplex themselvesfrom the outset:

I have been talking about the game of “thumb-catching.” What’swrong with that? “Thumb-catching”: holding the right thumb,say, in the left hand, then trying to grasp it with the right hand.The thumb “mysteriously” disappears before it can be grasped.(27n5)

How are we to avoid the Scylla of simply defining the hand as exclusivelyhuman, as did Bell, and the Charybdis of Wittgenstein’s thumb-catching,whereby a seemingly simple, working definition remains permanentlyelusive?10 The concepts of analogy and homology, as deployed byevolutionary biology, will prove helpful.

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The anatomist Richard Owen, some-time colleague and critic ofDarwin, was the first English writer to distinguish clearly, and thereby tostandardize, the terms analogy and homology. An analogue (from theGreek άνά meaning “up to” and λόγος meaning “ratio”) is the appropriatedescription for “a part or organ in one animal which has the same functionas another part or organ in a different animal” (668). A homologue, on theother hand (deriving from ομος meaning the “same”), is “the same organin different animals under every variety of form and function” (674).Owen was not entirely clear in explaining just what counts as “the same”organ in different animals, but Darwin himself adopted Owen’s terms, andelaborated definitions of his own which went some way to addressing theissue. Analogous structures are those that depend on similarity of function,as do the wings of insects and of birds for instance, whereas homologousorgans result from “their development from corresponding embryonicparts . . . as in the case of the arm of man, the fore-leg of a quadruped, andthe wing of a bird” (430, 434–35). An analogue, we might say, is that whichhas the same function, though it need not be the same organ; a homologue,on the other hand, is the same organ, though it need not have the samefunction. The elephant’s trunk, grasping at appetising herbage, may insome ways be analogous to the human hand, but it is by no means ahomologue of that appendage. Similarly, the panda’s “thumb,” though itappears in roughly the right position, and is very effectively employed togrip bamboo, is not a true thumb, since, as Gould has explained, it derivesfrom the radial sesamoid bone rather than from the corresponding bonesin a human hand (“The Panda’s Thumb”).11

Owen developed the concept of an archetype to explain the homologi-cal organs evident across vertebrate species. He viewed this archetype asa kind of Platonic model from which the frames of actual species areconstructed. He used a picture of the archetype for his personal emblem,and chose an appropriate maxim: “The motto is ‘the one in the manifold,’expressive of the unity of plan which may be traced through all themodifications of the pattern, by which it is adapted to the very habits andmodes of life of fishes, reptiles, birds, beasts, and human kind.”12 As Gouldexplains (“Eight Little Piggies” 63), Darwin considered this archetype “asmore than idea,” understanding it to represent, in fact, an ancestralvertebrate form. In amending the concept of homology to designate

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“development from corresponding embryonic parts” he gave to it a moreimmediately material meaning than Owen had intended. Owen, anevolutionist but one who rejected Darwin’s theory of natural selection, hadin mind a purely abstract “primal pattern,” not some ancestral species.Charles Bell, however, writing a little before Owen and Darwin, had beendeeply critical of all those “modern works on Natural History” whichsuppose “that the same elementary parts belong to all animals” (43). Herecognized that different creatures have similar organs in similar positions,but he argued that each of these creatures was specially designed,specially “adapted,” to their environment. Similarities between the organsof different species are the result of similarities in the functions that theyneed to fulfil (Bell 42–43, 166–70). In each case, organs are moulded bya Benevolent Creator with “perfect accommodation” to their uses (166),and attempts to find some underlying structure are no more than “verytrifling pursuits” which have the effect of “diverting the mind from thetruth” (43). Bell denied altogether the “very curious opinion” (168) thatelementary parts are “transposed” (43) in order to modify an archetypicalcreature to a particular environment. In short, Bell denied homology, ineither its idealist or materialist forms.

For Bell, then, species are individually created and therefore essen-tially unrelated, a view that the philosopher of science Ron Amundson hasdubbed taxonomic nominalism (32–34). The taxonomic nominalist doesnot deny the reality of species per se: they exist as distinct and uniqueentities in the world, to be sure. But for such a nominalist, the taxonomiccategories into which these entities are placed—genus, family, class,etc—do not represent objectively real relationships: such categories arepurely human creations. Those similarities between species or organs thatmight be identified are just that, mere similarities of form, coincidences thatare due entirely to similarities of function. For the taxonomic nominalist,then, similar organs in different species are never, strictly speaking(homologically), “the same.” Traces of this determinedly anti-homologicalperspective persist in the writings of those who would separate, absolutely,the human hand from the terminal organs of all nonhuman limbs. Heidegger,notoriously, would countenance no relation between the human hand andother varieties of vertebrate appendage. The human body is, for Heidegger,“something essentially other than an animal organism” (“Letter on

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Humanism” 228) precisely because it possesses the hand, which is“infinitely different” from the mere “grasping organs”—paws, claws, orfangs—of other creatures (What is Called Thinking 16). His insistenceon this distinction displays an implicit special adaptationism in which thehand evinces man’s unique place within Being.13

To the extent that humanistic thinkers insist on an absolute differencebetween species or between appendages, they exhibit a taxonomicnominalism as pronounced as Bell’s. When the human body is characterisedas “essentially other” than an animal organism, or the opposable thumb as“uniquely” human, taxonomic nominalism has already been assumed. Thewriter who denies that there might be nonhuman hands, who asserts thatthe difference between human hand and animal paw is “infinite,” does nomore than define the hand as human. Homology is by no means adequateto establish identity: hooves are not hands. But an implicit and uncriticalanthropocentrism here manifests as a vestigial taxonomic nominalism, adenial of structural homology, which precludes the very possibility ofrecognising identity between similarly-located appendages in differentspecies. Degrees and kinds of functional similarity, which might bemeasured or assessed, become irrelevant when the opportunity to identifyappendages as “the same” has already been ruled out. Such taxonomicnominalism sustains thereby a prejudicial rule of thumb, a long accepted,rough-and-ready measure of all things, which upholds Man as “the rulerover animate and inanimate nature.”

Inhuman Hands

Schopenhauer was outraged at the deceitful double-dealing so oftenencountered in considerations of the animal kingdom. More than once hefelt compelled to draw attention to the “vile and mean trick” wherebydifferent terms are employed in order to describe the activities and bodiesof animals, from those used for their human equivalents (Parerga andParalipomena 2.370). This miserable artifice is, he says, undoubtedly thework of “European priests and parsons,” and it is thus that they “concealunder a diversity of words the perfect and complete identity of the thing”(Basis of Morality 176–77). This duplicitous practice is evident when we

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consider the question of the nonhuman hand. Even should we grant Bellthat the elephant’s proboscis is only analogically a manus, and concede toGould his observations regarding the non-homological nature of thepanda’s thumb, there yet remain many pairs of hands which, though theydo not belong to human beings, should nonetheless be called by no othername. In his discussion of the thumb, Bell turns to the chimpanzee. Heprovides an illustration of the extremity of an “adult Chimpanzee, fromBorneo,” to demonstrate how the thumb extends no further than the rootof the fingers, which peculiarity distinguishes this member from the humanhand. This five fingered appendage he calls instead a paw (113–14).

Figure 1: Bones of Chimpanzee’s Paw.

Earlier in his treatise, Bell had already argued that monkeys do not havehands. He tells us that, although we might be tempted to describe the handas “an extremity in which the thumb and fingers are opposed to each other,so as to form an instrument of prehension,” we would thereby include theorgans of monkeys. But those monkey members are, he suggests, moreproperly to be considered feet, employed as they are for the purpose ofprogression by climbing and leaping through the branches of trees (18–19).The pragmatist philosopher and social psychologist George Herbert Meadreiterated precisely this point when he drew attention to the fact that thedominant function of a monkey’s “so-called hands” is locomotion (65).Further, the physician and primatologist John Napier, in his engaginglywide-ranging book Hands, could not quite bring himself to classify the

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monkey’s appendages as “true hands.” Employed in both a locomotor andmanipulatory role, these organs constitute a compromise, he argues: thecombination of “expert handling of objects with efficient locomotion”justifies our referring to a “foot-hand” (76).

Denying to monkeys the possession of “true hands,” or suggesting thatthey bear only feet, on the grounds that their grasping organs are employedfor brachiation, is unwarranted. Napier opens the chapter of his bookdevoted to the function of the hand with a discussion of opposition. Thisis, he says, perhaps the hand’s most important movement, which underliesall the skilled procedures of which it is capable. “The hand without a thumbis at worst, nothing but an animated fish-slice, and at best a pair of forcepswhose points don’t meet properly” (55). But, although opposition of thethumb is one of the hallmarks of humanity, it is not, Napier emphasises,unique to that species (56). Napier defines opposition more precisely thanis usual, as the movement “by which the pulp surface of the thumb is placedsquarely in contact with—or diametrically opposite to—the terminal padsof one or all of the remaining digits” (55). In addition to the requisiterotation of the thumb, a key factor in achieving this pulp-to-pulp contact isthe proportionate lengths of thumb and index finger: the shorter acreature’s thumb, the more difficult opposition becomes. The ratio of thesetwo digits is expressed as the “opposability index,” a figure calculated bymultiplying the length of an individual’s thumb by 100, and then dividing bythe length of the index finger (57). The opposability index provides a usefulindication of the manipulatory capacity of different hands. The meancalculation for those dextrous human hands, for instance, is 65. Most OldWorld monkeys are fully capable of opposing their thumbs, and thebaboons and mandrills in particular, whose opposability index lies closestto that of humans (mean: 57–58) are expert manipulators.14 Napierhimself recounts the delicate thumb and finger movements employed bothin feeding on seeds, grains and young grass shoots, and in the importantactivity of grooming. Though these appendages are also tasked with thebusiness of locomotion, they remain without question supreme manipula-tory organs. They are, as Schopenhauer would surely insist, hands byvirtue both of their structure and function.15

Even were we to permit Bell his monkey feet, what of that chimpanzee“paw”? What should we make of the five-fingered appendages of the

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apes? Bell argued that “it is upon the length, strength, free lateral motionand perfect mobility of the thumb, that the superiority of the human handdepends” and in this he was essentially correct (113–14). Opposition is byno means unique to the human hand, but what is distinctive about the“perfect” opposition of which the human thumb and fingers are capableis the “broad area of intimate contact between the finger-tip pulps of theopposing digits” (Napier 56). This greater area of sensitive contact, alongwith the complex underlying movements of opposing human fingers,makes possible the considerably more accomplished manipulation of smallor fragile items than is possible for other apes. Napier distinguished twobasic patterns of prehensile action, the power grip and the precision grip(62–66), and it is in the latter, which depends on a sophisticated form ofopposition, that the human hand excels.16 The chimpanzee thumb, bycontrast, although it is certainly opposed, is smaller and less dextrous thanin humans (mean opposability index: 43). A chimp will struggle to bring thethumb across the hand, to touch the tips of the ring and little fingers, andthese same fingers have difficulty crossing the hand in “ulnar opposition”to the base of the thumb (Wilson 24). As a result, the grip of thechimpanzee hand is neither so precise, nor so versatile, as that of thehuman.17

Galen had long ago drawn attention to the imperfections of the apehand. He was quite emphatic on the matter when he came to discuss thethumb:

Tell me, O noble sophists and clever accusers of Nature, have youever seen in the ape this finger that is commonly called the antihandand that Hippocrates calls the great finger? And if you have not seenthe ape’s thumb, will you have the effrontery to say that it is just likethe human thumb? If you have indeed seen one, I suppose you sawthat it is short, slender, distorted, and altogether ridiculous, just asthe ape’s whole body is. . . . Then what advantage is there in havingfour fingers well formed if the thumb is so poorly arranged that itcannot even be called the great finger? Surely this is its conditionin the ape, where it is separated only slightly from the forefinger, andis utterly ridiculous besides. And so, in this instance also, Natureis just, as Hippocrates often used to call her, because she hasbestowed a ridiculous body on an animal with a ridiculous soul.(1.22)18

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Galen has a good deal more to say about how ludicrous the ape is, prettyto children, but no more than a play-thing, a “laughable toy” (107). Theape’s hand, like the whole body, is no more than a caricature of the human,he suggests. But we should note that though this thumb may be small—perhaps even ridiculously small—and the hand may seem to him aludicrous, laughable distortion, Galen does not doubt for a moment both thatit is a thumb, and that we are dealing here with a hand.

Napier insists that apes possess true hands. Even when employed toassist in terrestrial locomotion, these members are not placed flat on theground like the “foot-hand” of the monkey, but are made to bear weighton the semi-clenched dorsal side, in the characteristic knuckle-walk of thegorilla and chimpanzee. These apes, Napier argues, walk not on feet buton their hands. Further, like monkeys, apes are expert in the handling ofobjects. Chimpanzees in particular, despite their small thumbs and lowopposability index, are enthusiastic tool users, employing a wide-ranging“tool kit” for a huge variety of tasks, from termite “fishing rods” tohammer-stones and weapons.19 Napier’s talk of “true hands” (76, 151)implies at times a prescriptive characterisation that recalls Heidegger’sabsolute separation of hand and merely “grasping organ,” and his use ofthe phrase “‘perfect’ opposition” (56, 59), despite the scare quotes, cannothelp but evoke Bell’s contention that the matchless human hand demon-strates divine design. Despite these echoes of an anti-evolutionaryanthropocentrism, however, Napier is fully committed to the essentialrelatedness of primate hands. Though they may be superficially unalike,laughably so if we share Galen’s sense of humour, Napier is emphatic that“the ape and human hand are cast from the same mould. . . . Dissimilaritiesbetween ape and human hands are largely quantitative” (76). These handsare homologous. It is by rejecting a prejudicial taxonomic nominalism, ahumanistic belief in hands that are “infinitely different” from all otherorgans, that we are able to recognise particular modes and degrees ofsimilarity. This is not to replace absolute difference with “perfect andcomplete identity”: the disparities between the hands of humans and thoseof other apes are many and varied (Wilson 130–32). Similarly, thoughopposable thumbs are by no means unique to human beings, even byNapier’s more demanding reckoning, they are employed by differentspecies in different ways. But in recalling the commonality of origin, the

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development from corresponding “embryonic parts,” we are prompted toappreciate that sufficient similarity here exists to designate ape andhuman appendage alike as hands. Bell presents us not with a “chimpanzee’spaw,” as he would have it, but a chimpanzee’s hand. Or does he?

Coda: A Murdered Child

Bell was wrong about the limb, but he was also mistaken regarding theidentity of its owner: not only was it a hand, but it did not belong to achimpanzee either. That short, thin thumb is characteristic of the orangu-tan (Napier 76), native to the islands of Borneo and Sumatra in South-eastern Asia; the chimpanzee, who has a slightly larger thumb, is anAfrican ape.20 The naturalist and explorer Alfred Russel Wallace took aparticular interest in orangutans during his expedition to the MalayArchipelago (1854–62). Having shot and examined a good number, heengaged in the ongoing debate, to which Owen himself had contributed,regarding the ape’s correct classification.21 In a paper published in 1856,he recounts how, after killing a mother orangutan, he acquired a baby andresolved to raise him (“Infant ‘Orang-Utan’”).22 The naturalist describesthe infant’s endearing antics as he was suckled with rice water and bathed,as he dangled nonchalantly from his specially constructed climbing frame,and as he clung tenaciously to Wallace’s beard. “When restless it wouldstruggle about with its hands up to catch hold of something, and might oftenbe seen quite contented when it had some bit of rag or stick grasped in twoor three of its hands.” (387) Wallace became quite enamoured, and wasmost upset when the inevitable came to pass. Maintained on an inadequatediet of biscuits and sweet potatoes, the orphaned orang died after just threemonths of captivity: “I much regretted the loss of my little pet . . . whichhad afforded me daily amusement and pleasure by its curious ways andthe inimitably ludicrous expressions of its little countenance.” (390)Wallace’s laughable toy was a play-thing no more.

It was just two years later, whilst suffering from some tropical fever,that, according to his own account, the principle of evolution by naturalselection occurred to Wallace in an Archimedean flash (WonderfulCentury 380–81; My Life 1.360–63). He dashed off a paper describing

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his theory, prompting a reluctant Darwin finally to make public the findingson which he had been sitting for so many years. Wallace’s paper waspresented, alongside Darwin’s, to the Linnaean Society in July 1858.Famously, however, Wallace would later break with Darwin on the matterof the extent to which natural selection can be employed as an explanatoryprinciple. Although it can probably account, he believed, for “all thevarieties of structure, all the wonderful adaptations, all the beauty of formand of colour, that we see in the animal and vegetable kingdoms,” Wallacedeveloped reservations when it came to the question of humanity. In apaper titled “The Limits of Natural Selection as Applied to Man,” Wallaceargued that humans possess a number of traits that go far beyondimmediate biological need—brain size, abstract thought, nakedness, voice,moral sense, consciousness—which must therefore have developed bysome means other than by natural selection.23 Additionally, he was unableto see how an organ as remarkable and “perfect” as the human hand, sofull of latent capacities that remained unrealised by “palæolithic man andhis still ruder predecessors,” could have evolved unless in anticipation ofthe needs of civilized man (“Limits of Natural Selection” 349). Apes, heasserted, “make little use of their separate fingers and opposable thumbs.They grasp objects rudely and clumsily, and look as if a much lessspecialized extremity would have served their purpose as well.” An“intelligent power” seemed to Wallace a much more likely explanationthan mere natural selection for this remarkable appendage which, heargued, is fully utilised as a hand only by humanity (349–50).

These were the old prejudices of human exceptionalism. Darwin, soonto publish the Descent of Man, was concerned for the welfare of theirtheory: “I hope you have not murdered too completely your own and mychild.”24 On reading Wallace’s arguments, he wrote to him: “As youexpected, I differ grievously from you, and I am very sorry for it. I can seeno necessity forcalling in an additional and proximate cause in regard toman.”25 Just as Wallace’s inadequate care had killed the infant orangutan,by seeking hands and “higher developments” outside the processes of hisown theory, Wallace deprived human evolution of its natural environment.A rule of thumb, as we saw, is an approximate but serviceable methodbased on past experience rather than precise calculation. Such pragma-tism has its place, but dangers arise when we fail to reflect on that

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experience, when an uncritical reliance on a tried and tested rule of thumbsanctions the repressive exercise of privilege and prejudice, when thethumb itself rules our thinking. The hand makes humans, we are told, notjust the supreme artisans of the animal kingdom, as Harris would have it,but, according to Bell, rulers over animate and inanimate nature; thatoppressive, opposable thumb secures universal dominion. But just as weshould free ourselves from the conviction that the downturned thumboriginated as a fate-sealing signal in the Colosseum, and from the folketymology that would derive the phrase “rule of thumb” itself fromdomestic abuse, so we should eschew the myth that opposable thumbs, andthus perfect hands, originate with humanity. There is no one, true Hand,evincing design or anything else, but a multitude of particular hands, eachgripping and grasping after their own fashion. We must guard against thelong established practice of assigning to humanity and its members someexceptional, mythic origin, lest we endanger both the integrity of ourthought, and the welfare of those to whom we would deny our commonancestry and homological affinity.

Oxford Brookes UniversityOxford, United Kingdom

Notes

1. The key text here is Kelly, though compare his interpretation of theevidence with that of Freyd and Johnson. The suggestion that woodworkingprovided the true origin of the phrase also has no supporting evidence (Kelly342, n6).

2. Outside the amphitheatre, it seems that a downturned thumb was actuallya sign of approbation, and an upturned thumb its opposite; see the thoroughaccount of the myths and misunderstandings surrounding ancient thumb ges-tures in Morris et al. (Chapter 16).

3. The team called this element “human-accelerated conserved noncodingsequence 1” (HACNS1) (“HACNS1 gene enhancer”). See Prabhakar et al.

4. The Romans, in fact, also called bear paws manus.5. See also p. 46. On this primitiveness, see also Tuttle (3).6. The human hand is not primitive in the sense that it is crude, of course:

successive modifications and refinements have made it an extremely delicate andaccomplished manipulative organ; see, e.g. Wilson (127–46).

7. See Clack.

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8. Jones concedes that such arguments are likely to appeal only to compara-tive anatomists from the kingdom of the Houyhnhnms (46).

9. See Gould’s discussion of the loss of digit number one (“Eight LittlePiggies” 69–74).

10. On the problems associated with defining the hand anatomically, seeWilson (8–9).

11. This did not stop the Romans also calling bear paws “manus.”12. Letter from Richard Owen to his sister Maria, 1852, quoted in Gould (“Eight

Little Piggies” 63). For discussion of Owen’s archetype, and Darwin’s transfor-mation of it into an ancestor, see Amundson (76–106).

13. I discuss the ostensive role played by Heidegger’s hand, and its parallelswith the special adaptationism of Genesis, elsewhere (“Like Water in Water”).

14. Lacking rotation and thus pulp-to-pulp contact, New World monkeys andprosimians exhibit only what has been called “pseudo-opposability” (Napier 58).

15. Napier refers to them as such, in fact, throughout the rest of his text.16. On the chimpanzee’s powerful “double-locking grip,” see Napier (27–28).17. On chimpanzee precision grips, see Butterworth and Itakura, and Marzke

(96–97, 103–04). On the importance of the overall “grasping repertoire” of thewhole hand, and not just the flexibility of the thumb, see Wilson (128–29), andespecially Marzke, whose work complicates the degrees and modes of precisiongripping, and moves beyond its equation with relative thumb length. On theevolution of the human thumb, its muscles, and the complex range of movementsof which it is capable, see Wilson (136–39).

18. The “apes” dissected by Galen were actually baboons and Barbarymacaques, a species of tail-less monkey; see Morris and Morris (123).

19. See McGrew, especially the tables listing tools organised by regionaldifferences amongst cultural groups (177–97). On orangutan material culture, seevan Schaik, et al.

20. The size, shape and arrangement of the metacarpals, phalanges andscaphoid bones further indicate that this can only have belonged to an orangutan;Colin Groves, personal communication. Illustrations comparing the hands of anumber of apes and monkeys can be found in Schultz (reprinted in Jones andLederman 13 and, partially, in Wilson 22), and in de Waal and Lanting (27).

21. By his own count, Wallace shot sixteen orangutans during the expedition;see Wallace (“On the Orang-Utan”) and Wallace (Malay Archipelago 51-74).

22. The account is repeated, with minor changes, in The Malay Archipelago(53-57).

23. This paper developed ideas that Wallace had briefly voiced, anony-mously, the year before (“Charles Lyell”).

24. Darwin to Wallace, 27 March 1869 (More Letters 2.39).25. Darwin to Wallace, 14 April 1869 (Life and Letters 2.116).

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