Hen’s Teeth and Horse’s Toes (17 page)

Homeosis is easiest to demonstrate in arthropods with their characteristic body plan of discrete segments with different and definite fates in normal development, but common embryological and evolutionary origins. Yet analogous phenomena have been noted again and again in other animals and plants with repeated parts. In fact, Bateson’s first example after defining the term cited vertebrae in the human backbone. All mammals (except sloths, but including giraffes) have seven cervical, or neck, vertebrae (they are awfully large in giraffes). These are followed by dorsal, or rib-bearing, vertebrae. Bateson noted numerous cases of humans with ribs on the seventh, and even a few with ribs on the sixth, cervical vertebra.

Homeotic mutants are gripping in their weirdness, but what do they teach us about evolution? We must avoid, I believe, the tempting but painfully naïve idea that they represent the long-sought “hopeful monsters” that might validate extreme saltationist views of major evolutionary transitions in single steps (a notion that I, despite my predilections for rapid change, regard as a fantasy born of insufficient appreciation for organisms as complex and integrated entities). First of all, most homeotic mutations produce hopeless creatures. The legs that extend from antennal sockets or surround mouths in afflicted flies are useless appendages without proper neural and muscular hookups. Even if they did work, what could they accomplish in such odd positions? Secondly, the viable homeotics mimicking ancestral forms are not really forebears reborn. A bithorax fly bears the ancestral complement of four wings, but it attains this state by growing two second thoraxes, not by recovering an ancient pattern.

I believe that the lessons of homeosis lie first in embryology and then cycle back to evolution. As Tom Kaufman pointed out to me, they demonstrate in a dramatic way how few genes are responsible for regulating the basic order of developing parts in a fruit fly’s body. Together, the ANT-C and BX-C complexes of
D. melanogaster
specify the normal development of all the mouth, thoracic, and abdominal segments—only the two anterior segments are not subject to their control. Each complex contains only a handful of genes and each handful may have evolved from a single ancestral gene that repeated itself several times. When these genes mutate or are deleted, peculiar homeotic effects arise that usually throw development awry and lead to death.

Most importantly perhaps, these homeotic complexes display the hierarchical way in which genetic programs regulate the immense complexity of embryonic development, recognized since Aristotle’s time as biology’s greatest mystery. The homeotic genes do not build the different structures of each body segment themselves. This is the role of so-called structural genes that direct the assembly of proteins. The homeotics are switches or regulators; they produce some signal (of utterly unknown nature) that turns on whole blocks of structural genes.

Yet, at a higher level, some master regulator must be responsible for turning on the homeotics at the right time and in the right place, for we know that many homeotic mutations are mistakes in placement and timing. Perhaps this master regulator is no more than a gradient of some substance running from the front to the back end of a larval fly; perhaps the homeotic regulators can “read” this gradient and turn on in the right place by assessing its concentration. In any case, we have three hierarchical levels of control: the structural genes that build different parts in each segment, the homeotic regulators that switch on the blocks of structural genes, and the higher regulators that turn on the homeotic regulators in the right place and at the right time.

If embryology is a hierarchical system with surprisingly few master switches at high levels, then we might draw an evolutionary message after all. If genetic programs were beanbags of independent genes, each responsible for building a single part of the body, then evolution would have to proceed bit by bit, and any major change would have to occur slowly and sequentially as thousands of parts achieved their independent modifications. But genetic programs are hierarchies with master switches, and small genetic changes that happen to affect the switches might engender cascading effects throughout the body. Homeotic mutants teach us that small genetic changes can affect the switches and produce remarkable changes in an adult fly. Major evolutionary transitions may be instigated (although not finished all at once as hopeful monster enthusiasts argue) by small genetic changes that translate into fundamentally altered bodies. If classical Darwinian gradualism is now under attack in evolutionary circles, the hierarchical structure of genetic programs forms a powerful argument for the critics.

In this context, we consider the hypothetical major steps in insect evolution and recognize that homeotic mutants may help to illuminate them. Insects, with their relatively few, differentiated segments, probably evolved from an ancestor with more numerous and less differentiated segments. Initially, these less differentiated segments each bore a pair of legs (the antennae and mouthparts of modern insects are modified legs). Insects evolved by suppressing legs on the posterior segments and modifying them to antennae and mouthparts on the anterior segments. The major homeotic complexes of
Drosophila
seem to regulate just these changes—and with a minimum of genetic information. BX-C controls the posterior appendages with their suppressed legs, and its deletion causes these segments to begin a differentiation as second thoracics with incipient legs. The major mutants of ANT-C replace structures that were once legs with legs. The nature of homeotic changes is not capricious, but follows evolutionary channels.

Even the bizarre homeotics may not be devoid of evolutionary information. When Bridges and Dobzhansky described proboscipedia in 1933, they noted that a large set of coordinated changes—quite apart from the spectacular appearance of legs—all brought the mouthparts closer to the standard form of biting insects from which flies presumably evolved. (Dobzhansky, who died just a few years ago, was the greatest evolutionary geneticist of our times. Fancy, quantitative lab work often wins all the kudos while field naturalists, with their detailed and specific knowledge, are unfairly dismissed as stamp collectors. Dobzhansky’s life proves how misguided this prejudice is. Geneticists had been describing homeotic mutants for years, but none had the knowledge to recognize the subtle morphological effects that require a trained taxonomist’s eye to comprehend. Dobzhansky, the finest geneticist of them all, was a trained taxonomist and field biologist who began his work by specializing on the systematics of the Coccinellidae, or lady beetles. There is no substitute for detailed knowledge of natural history and taxonomy.)

If anyone has wondered whether homeotic mutants must find their significance only in highfalutin realms of evolutionary speculation, I close with an arresting fact. A homeotic mutation has been found in the biting mosquito
Aedes albopictus
. Yes, you guessed it. This mutation converts part of the biting apparatus into a pair of legs! The six stylets that actually pierce our skin are unaffected, but the labella, the structures that surround the stylets and contain tactile and chemosensory hairs, are converted to legs with tarsal claws at their tips. These mosquitos cannot pierce skin, both because they lack the tactile and chemosensory hairs that locate the right spot and because the stylets get entrapped in the misplaced legs.

What a wonderful and joyous idea in a world inundated with bad news—an ouchless mosquito with an extra pair of legs. Oh, don’t raise your hopes. They won’t replace the normal ones. First of all, they die because they cannot feed (although they can be artificially maintained on blood-soaked cotton balls). Even if they learned to feed by lapping instead of piercing, they would be no match for the normal kind because they have longer larval lives, increased pupal mortality, and a significant decrease in adult longevity. Still, these are the curious facts that nurture hope in parlous times—in this case, and with only a little poetic license, an enormous advantage (if only for another long-suffering creature) of putting a foot in one’s mouth.

Introduction and Background

OF CONSPIRACIES

IN HIS GREAT ARIA
“La calunnia,” Don Basilio, the music master of Rossini’s
Barber of Seville
, graphically describes how evil whispers grow, with appropriate watering, into truly grand and injurious calumnies. For the less conniving among us, the same lesson may be read with opposite intent: in adversity, try to contain. The desire to pin evil deeds upon a single soul acting alone reflects this strategy; conspiracy theories have a terrible tendency to ramify like Basilio’s whispers until the runaway solution to “whodunit” becomes “everybodydunit.” But conspiracies do occur. Even the pros and pols now doubt that Lee Harvey Oswald acted alone; and everybody did do it on the Orient Express.
²

The Piltdown case, surely the most famous and spectacular fraud of twentieth-century science, has experienced this tension ever since its exposé in 1953. The semiofficial, contained version holds that Charles Dawson, the lawyer and amateur archeologist who “found” the first specimens, devised and executed the entire plot himself. Since J. S. Weiner’s elegant case virtually precludes Dawson’s innocence (
The Piltdown Forgery
, Oxford University Press, 1955), conspiracies become the only reasonable refuge for challengers. And proposals for coconspirators abound, ranging from the great anatomist Grafton Elliot Smith to W. J. Sollas, professor of geology at Oxford. I regard these claims as farfetched and devoid of reasonable evidence. But I do believe that a conspiracy existed at Piltdown and that, for once, the most interesting hypothesis is actually true. I believe that a man who later became one of the world’s most famous theologians, a cult figure for many years after his death in 1955, knew what Dawson was doing and probably helped in no small way—the French Jesuit priest and paleontologist Pierre Teilhard de Chardin.

TEILHARD AND PILTDOWN

Teilhard, born in Auvergne (central France) in 1881, belonged to an old, conservative, and prosperous family. Entering the Society of Jesus in 1902, he studied on the English island of Jersey from 1902 to 1905 and then spent three years as a teacher of physics and chemistry at a Jesuit school in Cairo. In 1908, he returned to finish his theological training at the Jesuit seminary of Ore Place in Hastings, providentially located right next to Piltdown on England’s southeast coast. Here he stayed for four years, and here he was ordained a priest in 1912.
³
As a theological student, Teilhard was talented enough, but lackadaisical. His passion at Hastings was, as it always had been, natural history. He scoured the countryside for butterflies, birds, and fossils. And, in 1909, he met Charles Dawson at the focus of their common interests—in a stone quarry, hunting for fossils. The two men became good friends and colleagues in pursuit of their interest. Teilhard described Dawson to his parents as “my correspondent in geology.”

Dawson claimed that he had recovered the first fragment of Piltdown’s skull in 1908, after workmen at a gravel pit told him of a “coconut” (the entire skull) they had unearthed and smashed at the site. Dawson kept poking about, collecting a few more skull pieces and some fragments of other fossil mammals. He did not bring his specimens to Arthur Smith Woodward, keeper of paleontology at the British Museum, until the middle of 1912. Thus, for three years before any professional ever heard of the Piltdown material, Dawson and Teilhard were companions in natural history in the environs of Piltdown.

Smith Woodward was not a secretive man, but he knew the value of what Dawson had brought and the envy it might inspire. He clamped a tight lid upon Dawson’s information prior to its publication. He wanted none of Dawson’s lay friends at the site, and only one naturalist accompanied Dawson and Smith Woodward in their first joint excavations at Piltdown—Teilhard de Chardin, whom Dawson had described as “quite safe.” More specimens came to light during 1912, including the famous jaw with its two molar teeth, artificially filed to simulate human patterns of wear. In December, Smith Woodward published and the controversy began.

The skull fragments, although remarkably thick, could not be distinguished from those of modern humans. The jaw, on the other hand, except for the wear of its teeth, loudly said “chimpanzee” to many experts (in fact, it once belonged to an orangutan). No one smelled fraud, but many professionals felt that parts of two creatures had been mixed together at the Piltdown site. Smith Woodward stoutly defended the integrity of his creature, arguing, with flawed logic, that the crucial role of brain power in our mastery of the earth today implies a precocious role for large brains in evolutionary history as well. A fully vaulted skull still attached to an apish jaw vindicated such a brain-centered view of human evolution.

Teilhard left England late in 1912
⁴
to begin his graduate studies with Marcellin Boule, the greatest physical anthropologist of France. But in August 1913, he was back in England for a retreat at Ore Place. He also spent several days prospecting with Dawson and on August 30 made a major discovery himself—a canine tooth of the lower jaw, apish in appearance but worn in a human fashion. Smith Woodward continued his series of publications on the new material, but critics persisted in their belief that Piltdown man represented two animals improperly united.

The impasse broke in Smith Woodward’s favor in 1915. Dawson had been prospecting at another site, two miles from Piltdown, for several years. He probably took Teilhard there in 1913; we know that he searched the area several times with Smith Woodward in 1914. Then, in January 1915, he wrote to Smith Woodward. The second site, later called Piltdown 2, had yielded its reward: “I believe we are in luck again. I have got a fragment of the left side [it was actually the right] of a frontal bone with a portion of the orbit and root of nose.” In July of the same year, he announced the discovery of a lower molar, again, apish in appearance but worn in a human fashion. The bones of a human and an ape might wash into the same gravel pit once, but the second, identical association of vaulted skull and apish jaw surely proved the integrity of a single bearer, despite the apparent anatomical incongruity. H. F. Osborn, America’s leading paleontologist and critic of the first Piltdown find, announced a conversion in his usual grandiloquent fashion. Even Teilhard’s teacher Marcellin Boule, leader of the doubters, grumbled that the new finds had tipped the balance, albeit slightly, in Smith Woodward’s favor. Dawson did not live to enjoy his triumph, for he died in 1916. Smith Woodward stoutly supported Piltdown for the rest of his long life, devoting his last book (
The Earliest Englishman
, 1948) to its defense. He died, mercifully, before his bubble burst.

Meanwhile, Teilhard pursued his calling with mounting fame, frustration, and exhilaration. He served with distinction as a stretcher bearer in World War I and then became professor of geology at the Institut Catholique of Paris. But his unorthodox (although always pious) thinking soon led him into irrevocable conflict with ecclesiastical authority. Ordered to abandon his teaching post and to leave France, Teilhard departed for China in 1926. There he remained for most of his life, pursuing distinguished research in geology and paleontology and writing the philosophical treatises on cosmic history and the reconciliation of science with religion that later made him so famous. (They all remained unpublished, by ecclesiastical fiat, until his death.) Teilhard died in 1955, but his passing only marked the beginning of his meteoric rise to fame. His treatises, long suppressed, were published and quickly translated into all major languages.
The Phenomenon of Man
became a best seller throughout the world. Harvard’s Widener Library now houses an entire tier of books devoted to Teilhard’s writing and thinking. Two journals that were established to discuss his ideas still flourish.

Of the original trio—Dawson, Teilhard, and Smith Woodward—only Teilhard was still living when Kenneth Oakley, J. S. Weiner, and W. E. le Gros Clark proved that the Piltdown bones had been chemically stained to mimic great age, the teeth artificially filed to simulate human wear, the associated mammal remains all brought in from elsewhere, and the flint “implements” recently carved. The critics had been right all along, more right than they had dared to imagine. The skull bones did belong to a modern human, the jaw to an orangutan. As the shock of revelation gave way to the fascination of whodunit, suspicion quickly passed from two members of the trio. Smith Woodward had been too dedicated and too gullible; moreover, he knew nothing of the site before Dawson brought him the original bones in 1912. (I have no doubt whatsoever of Smith Woodward’s total innocence.) Teilhard was too famous and too present for any but the most discreet probing. He was dismissed as a naïve young student who, forty years before, had been duped and used by the crafty Dawson. Dawson acting alone became the official theory; professional science was embarrassed, but absolved.

DOUBTS

I was just the right age for primal fascination—twelve years old—and a budding paleontologist when news of the fraud appeared on page one of the
New York Times
one morning at breakfast. My interest has never abated, and I have, over the years, asked many senior paleontologists about Piltdown. I have also remarked, both with amusement and wonder, that very few believed the official tale of Dawson acting alone. I noted, in particular, that several of the men I most admire suspected Teilhard, not so much on the basis of hard evidence (for their suspicions rested on what I regard as a weak point among the arguments), but from an intuitive feeling about this man whom they knew well, loved, and respected, but who seemed to hide passion, mystery, and good humor behind a garb of piety. A. S. Romer and Bryan Patterson, two of America’s leading vertebrate paleontologists and my former colleagues at Harvard, often voiced their suspicions to me. Louis Leakey voiced them in print, without naming the name, but with no ambiguity for anyone in the know (see his autobiography,
By the Evidence
).
⁵

I finally decided to get off my butt and probe a bit after I wrote a column on Piltdown for other reasons (
Natural History
, March 1979). I read all the official documents and concluded that nothing excluded Teilhard, although nothing beyond his presence at Piltdown from the start particularly implicated him either. I intended to drop the subject or to pass it along to someone with a greater zeal for investigative reporting. But at a conference in France last September, I happened to meet two of Teilhard’s closest colleagues, the leading paleontologist J. Piveteau and the great zoologist P. P. Grassé. They greeted my suspicions with a blustering “
incroyable
.” Then Père François Russo, Teilhard’s friend and fellow Jesuit, heard of my inquiries and promised to send me a document that would prove Teilhard’s innocence—a copy of the letter that Teilhard had written to Kenneth Oakley on November 28, 1953. I received this letter in printed French translation (Teilhard wrote it in English) in October 1979 and realized immediately that it contained an inconsistency (a slip on Teilhard’s part) most easily resolved by the hypothesis of Teilhard’s complicity. When I visited Oakley at Oxford in April 1980, he showed me the original letter along with several others that Teilhard had written to him. We studied the documents and discussed Piltdown for the better part of a day, and I left convinced that Romer, Patterson, and Leakey had been right. Oakley, who had noted the inconsistency but interpreted it differently, agreed with me and stated as we parted: “I think it’s right that Teilhard was in it.” (Let me here express my deep appreciation for Dr. Oakley’s hospitality, his openness, and his simple, seemingly inexhaustible kindness and helpfulness. I always feel so exhilarated when I discover—and it is not so rare as many people imagine—that a great thinker is also an exemplary human being.) Since then, I have sharpened the basic arguments and read through Teilhard’s published work, finding a pattern that seems hard to reconcile with his innocence. My case is, to be sure, circumstantial (as is the case against Dawson or anyone else), but I believe that the burden of proof must now rest with those who would hold Father Teilhard blameless.

The Case against Teilhard

THE LETTERS TO KENNETH OAKLEY

The main virtue of truth, quite apart from its ethical value (which I hold to be considerable), is that it represents an infallible guide for keeping your story straight. The problem with prevarication is that, when the going gets complex or the recollection misty, it becomes very difficult to remember all the details of your invented scheme. Richard Nixon finally succumbed on a minor matter, and Sir Walter Scott spoke truly when he wrote the famous couplet: “Oh, what a tangled web we weave,/When first we practice to deceive!”

Teilhard made just such a significant slip on a minor point in his letter to Oakley. Teilhard offered no spontaneous recollections about Piltdown and responded only to Oakley’s direct inquiries for help in establishing the forger’s identity. He begins by congratulating Oakley “most sincerely on your solution of the Piltdown problem. Anatomically speaking, ‘
Eoanthropus
’ [Smith Woodward’s name for the Piltdown animal] was a kind of monster…. Therefore I am fundamentally pleased by your conclusions, in spite of the fact that, sentimentally speaking, it spoils one of my brightest and earliest paleontological memories.”

Teilhard then stonewalls on the question of fraud. He refuses to believe it at all, declaring that Smith Woodward and Dawson (and, by implication, himself) were not the kind of men who could conceivably do such a thing. Is it not possible, he asks, that some collector discarded the ape bones in a gravel pit that legitimately contained a human skull, the product of a recent interment? Could not the iron staining have been natural, since the local water “can stain (with iron) at a remarkable speed”? But Teilhard’s notion can explain neither the artificial filing of the teeth to simulate human wear nor the crucial discovery of a second combination of ape and human at the Piltdown 2 site. In fact, Teilhard admits: “The idea sounds fantastic. But, in my opinion, no more fantastic than to make Dawson the perpetrator of a hoax.”