Mutants

by Armand Marie Leroi

  By ‘linear proportions’ I mean the relative lengths of torso, arms and legs. Pygmy men have the broad chest and shoulders of adult men anywhere, and pygmy women have fully adult breasts and hips. But the juvenile linear proportions of pygmies immediately suggest two devices by which they should come to be so small. Perhaps they simply stop growing at age eleven. Alternatively, perhaps they grow for as long as taller people do (until age eighteen or so), but very slowly.

  In principle it should be easy to distinguish between these two ways of being small – it is just a matter of measuring many pygmy children of known age to see when they stop growing. But pygmies do not know how old they are. They have no calendar and so no interest in birthdays. Occasionally, however, pygmy children have been measured. Schweinfurth traded a dog for an Aka called Nsévoué and attempted to bring him back to Europe, but they did not get far before the child succumbed to dysentery. In 1873 another attempt was made, but this time it was the explorer who died. Giovanni Mani, an Italian following Schweinfurth’s trail, traded a dog and a calf for two Aka children, Thibaut and Chair-Allah, and headed north only to expire from the rigours of his journey. The children, however, went on and arrived in Rome in June 1874, where they were presented to King Victor Emmanuel II and then bequeathed, along with Mani’s diaries, to the Geographical Society of Italy.

  The geographers, entranced by their acquisition but puzzled what to do with it, passed the children on to Count Miniscalchi-Errizo, a Veronese nobleman. Redubbed Francesco and Luigi, they flourished under the good Count’s care and were soon speaking, reading and writing Italian with panache. Thibaut-Francesco taught himself piano and would pick out delicate airs though his fingers spanned less than an octave. Schweinfurth visited the boys in 1876 and recorded with delight the sight of them sauntering down the streets of ancient Verona with local friends.

  THIBAUT-FRANCESCO AND CHAIR-ALLAH-LUIGI, VERONA C.1874. FROM ARMAND DE QUATREFAGES 1895 THE PYGMIES.

  The intellectual progress of the two boys was much commented on in the scholarly journals of the day, not least because it refuted the belief that pygmies might not be too bright. That this notion existed at all was partly Schweinfurth’s fault. Although he had evidently been fond of Nsévoué, the published account of his travels, The heart of Africa, gives a rather damning estimate of his friend’s ability and character. But the learned men who streamed through the Palazzo Miniscalchi to view Chair-Allah-Luigi and Thibaut-Francesco were less interested in the boys’ conversation than in simply standing them against a wall and measuring them. Before they had even left Africa, Chair-Allah-Luigi and Thibaut-Francesco had been measured by at least seven scientists, and the pace picked up in Rome. The age of the boys remains in some doubt, but they were thought to be eight and twelve when they arrived in Italy, and they lived there for nearly six years. As they grew, a curious thing was noticed. They didn’t have a pubertal growth spurt.

  A newborn infant grows about eighteen centimetres (seven inches) in its first year. This extraordinary rate is not maintained; rather it drops smoothly, year by year, to about five centimetres (two inches) per year. At around the age of twelve for boys, ten for girls, this decline is reversed and growth rate leaps up, albeit only temporarily. Although familiar to any adolescent, the pubertal growth spurt is a rather difficult thing to measure. In 1759 the French aristocrat and friend of Buffon, Philibert Guéneau de Montbeillard (yet another count), began measuring his newly born son, and continued to do so at six-monthly intervals until the boy’s eighteenth birthday. This same boy was eventually guillotined by Robespierre, but the record of his growth remains one of the most perfect of its kind. Though de Montbeillard – or rather Buffon, who wrote up the results –failed to realise it, the data show a beautiful pubertal growth spurt. At the age of thirteen, de Montbeillard’s son’s growth rate spiked at twelve centimetres (nearly five inches) per year. This is a very human thing. Male chimpanzees and gorillas pack on muscle at adolescence and baboons’ snouts elongate, but no other primate shows this sort of skyward leap.

  The pubertal spurt is driven by a burst of growth hormone. Pygmies might, then, be expected to have growth hormone levels much lower than those of taller people; but curiously, they don’t. Their shortness seems to be due to a relative lack of another growth-promoting molecule called insulin-like growth factor-1, or IGF-1. As implied by its name, IGF-1 is structurally rather similar to insulin – the hormone of sugar metabolism. Growth hormone regulates the IGF gene so that levels of the two hormones in the bloodstream tend to rise and fall in synchrony. But each hormone makes a unique contribution to growth.

  The proof of this is the mini-mouse. A normal laboratory mouse weighs around thirty grams when fully grown. This is rather larger than Mus musculus in its natural habitat (cellars, attics, barns); generations of la dolce vita in the world’s laboratories have made the geneticist’s mouse tame, slow, and slightly corpulent. Be that as it may, if a defective growth-hormone receptor gene is engineered into a laboratory mouse (rather as occurs naturally in Ecuadorean dwarfs), it grows up to be only half the size of a normal mouse. If a defective IGF gene is engineered into another mouse it grows up to about one third the normal size. If these two miniature mice are crossed, the result is the mini-mouse in which both genes are defective and that weighs, when fully grown, only five grams.

  This, for a mammal, is minute. It is almost as small as the smallest of all mammals, the bumblebee bat of Thailand, which weighs around two grams. A British five-pence piece weighs 3.2 grams; a euro-cent 2.4 grams; a dime two grams. An adult human that was the same relative size as a mini-mouse would weigh as much as a fourteen-month-old child – a result that suggests that neither the pygmies of the Congo, nor the dwarfs of Ecuador, nor even Joseph Boruwlaski, small as they are, even begin to approach the limits of human smallness.

  CRETINS

  Schweinfurth’s discovery set off a global hunt for other pygmies. Little people had always cropped up in explorers’ logs and local myths in this or that part of the globe. Such tales had never received much credence, but in the 1890s they were assiduously collected and analysed. Suddenly there seemed to be pygmies in Guatemala, the Yucatan, the Cascade Range of British Columbia, the Atlas Mountains of Morocco, Sicily and the Val de Ribas of Spain. An archaeologist claimed the existence of a race of Neolithic pygmies in Switzerland. Perhaps all these little people were related; perhaps they were the remnants of an earlier, shorter, version of humanity.

  The fossil record shows otherwise. Our direct ancestor, Homo erectus, was about 160 centimetres (five feet two inches) tall; Homo neanderthalensis was about 170 centimetres (five feet six inches) tall; and early anatomically modern humans (‘Cro-Magnon man’) were only a little shorter. To be sure, there are short people in various parts of the world. Adult men of the Yanomamo tribe who live at the headwaters of the Orinoco and Amazon rivers have an average height of only 153 centimetres (five feet). The Papua New Guinean highlanders who live on Mount Goliath are also small. The enormous differences among people from around the globe show that the size we are is very malleable. We cannot be sure that smallness evolved independently in African pygmies and Asian negritos, but elsewhere in the world, smallness has evolved again and again.

  I say evolved, but a note of caution is required. Most small people live in remote and impoverished parts of the world. It is difficult to know just how tall they would be if fed a protein-and calorie-rich supermarket diet. No one believes that African pygmies would grow much taller if transported en masse to California, but we would do well to remember that the children of Mayan refugees who moved to Los Angeles in the 1970s gained an additional 5.5 centimetres (about two inches) over their relations who stayed in Guatemala.

  It is even possible that the most recent, and probably the last, pygmy tribe to be discovered will prove not to be pygmies at all, but rather people with a severe and rather specific nutritional deficiency. In 1954 a Burmese soldier marching through the montane forests near the joint fronti
ers of Burma, India, Tibet and China came across a village of small people. He was not quite the first to do so. Before Burma’s independence, a series of British explorers – lean, lone Indian Army officers – had traversed back and forth across the region where the four great rivers of Asia, the Irrawaddy, Salween, Mekong and Yangtse, descend from the Tibetan Plateau. Their reports are scanty, but consistent. They record the existence of an ethnically distinct group of ‘dwarfs’ who seemed to have their centre in the upper reaches of the valley of the Taron, a remote tributary of the Irrawaddy. The dwarfs were variously called Darus, Nungs, Naingvaws, Hkunungs or Kiutzu. They were elusive and no one had studied them at any length, yet most accounts agreed that they were a cheerful and hardy, if notably dirty, people who tattooed their faces, lived in tree houses, and were often enslaved by the taller hill-tribes such as the Lisu. A Captain B.E.A. Pritchard measured some Nungs and found they had an average height of 158 centimetres (five feet two inches). He later drowned while trying to ford the Taron after the Nungs cut the bridge that spanned it.

  In 1962 the Burmese government decided to find out more. A caravan of military men and physicians walked for two weeks across razor-backed ridges and rope-bridged ravines to the Taron Valley. Their study was published in one of the world’s most obscure journals, the Proceedings of the Burma Medical Research Society, but it is clear and comprehensive. The Burmese found ninety-six people living in two villages. Disappointingly, there were no tree houses and no tattoos, but the men had an average height of only 144 centimetres (four feet eight inches). This was as short as the shortest African pygmies. Yet these people, who called themselves Taron after the river on which they lived, were clearly of Tibeto-Burman stock, and spoke a Tibeto-Burman language. Subsistence farmers of a meagre sort, they lived in conditions of abject poverty and squalor. Three generations previously, the Taron said, they had crossed over from Yunnan; a landslide had blocked the pass through which they had come and they had been in Burma ever since.

  DARU OR TARON. UPPER BURMA C.1937.

  Who were they? The Burmese weighed up the evidence and decided that the Taron were probably identical to the Nungs of earlier reports, and therefore a race of genetically short people. How many more of them there were, and their precise origins, were questions left unanswered. The hypothesis that they were true pygmies appeared to be supported by the fact that they lived in close proximity to taller people whose diets seemed no worse than theirs. Yet there were disquieting aspects to the Taron. Of the ninety-six living in the two villages, nineteen were mentally defective. This is a high proportion, even allowing for the fact that they were inbred (pedigrees showed many first-cousins marriages). Several had severe motor-neuron disorders and were unable to walk. And the Taron themselves claimed that when they had come from China they had been of normal size; only in Burma had they become small. That is all we know of the Taron, and we are not likely to know more soon – foreigners have not been allowed into Upper Burma for decades. But it is possible that the Taron are not so much pygmies, or even dwarfs, but rather simply cretins.

  It is not a pretty word, but it is the correct one. Cretins are people who are afflicted from birth by a mix of neurological and growth disorders. Traditionally, they have been classified into two types: ‘neurological’ cretins who are mentally defective, have severe motor-neuron problems and tend to be deaf-mute; and ‘myxedematous’ cretins who have severely stunted growth, dry skin, an absence of eyelashes and eyebrows and a delay in sexual maturity. A peculiarly vicious form of myxedematous cretinism, in which growth and sexual development simply stop at about age nine, is found in the Northern Congo. These Congo cretins may be in their twenties and still show no sign of breasts or pubic hair, menstruation or ejaculation, and they never grow taller than 100 centimetres (three feet three inches). This is an extreme. The Taron may have a milder form of the same disease.

  Cretinism is a global scourge. In 1810 Napoleon Bonaparte ordered a survey of the inhabitants of the Swiss canton of Valais; his scientists found four thousand cretins among the canton’s seventy thousand inhabitants. The location is telling. As the Taron Valley lies in the foothills of the Himalayas, so Valais lies at the base of the Alps. Swiss cretins have not been spotted since the 1940s, but a belt of cretinism still tracks most of the world’s other great mountain ranges: the Andes, the Atlas, the New Guinea highlands, the Himalayas. What these areas have in common is a lack of iodine in the soil. People and animals alike rely on their food for a ready supply of iodine, but in many parts of the world, especially at high altitude, glaciation and rainfall have leached most of the iodine out of the soil so that the very plants are deprived. Cretinism is caused by a diet that contains too little iodine. Globally, about one billion people are at risk of iodine deficiency; six million are cretins.

  MYXDEMATOUS CRETINS AGED ABOUT TWENTY, WITH NORMAL MAN. CONGO REPUBLIC 1970.

  In the Gothic cathedral of Aosta, ten kilometres south-east of Mont Blanc, the choir stalls are decorated with portraits of cretins. They were carved to keep their fifteenth-century viewers mindful of the unpleasantness of Eternal Torment: a local version of the fabulous creatures and demonic creatures of misericords elsewhere. Many of the cretins have a curious feature: their necks are bulging and misshapen; one even has a bi-lobed sack of flesh hanging from his throat large enough to grasp with both hands. Just over a hundred years after Aosta Cathedral was built, Shakespeare would write in The Tempest: ‘When we were boys/Who would believe that there were mountaineers/Dew-lapp’d like bulls, whose throats had hanging at them/Wallets of flesh?’

  The Aosta cretins and Shakespeare’s mountaineers were goitrous. Goitre is an external manifestation of an engorged thyroid, a butterfly-shaped organ located just above the clavicles. Like cretinism, it is a sure sign of iodine deficiency. When first discovered in 1611, the thyroid was thought to be a kind of support for the throat, a cosmetic device to make it more shapely. In fact it is a gland that makes and secretes a hormone called thyroxine. The thyroid needs iodine to make this hormone, and should iodine become scarce, the thyroid attempts to restore order by the rather drastic device of growing larger. The result is at first a swollen neck, then a bulging neck, and finally, in elderly people who have lacked iodine all their lives, an enormous bag of tissue that spreads from beneath the chin onto the chest, and that contains vast numbers of thyroid tissue nodules, some of which are multiplying, others of which are dying, yet others of which are altogether spent. In England this is called ‘Derbyshire neck’.

  A goitre is an ugly but useful thing to have, particularly for a pregnant woman. Thyroxine is yet another hormone, albeit not a protein, that promotes cell proliferation in the bones of foetuses and growing children. It also controls the number of cells that migrate down the growth plate to swell and die before forming bone. A foetus gets the thyroxine it needs from its mother; should it not get enough it is born cretinous. Lack of dietary iodine during childhood can also cause cretinism. And cretinism can also be, albeit rarely, a genetic disease. Many human mutations are known that disrupt the production of thyroxine, its storage, its transport around the body, or its ability to dock to its receptor.

  There is also a class of mutations more vicious by far than those that simply cause thyroid malfunction. These mutations affect the pituitary. Among the hormones that the pituitary produces is one that controls the thyroid. This hormone, thyrotropin, regulates the way that the thyroid absorbs iodine, the rate at which it manufactures thyroid hormone, and the way it grows and shrinks according to need. The pituitary is the thyroid’s check and its balance. Goitre is a witness to its workings. The pituitary monitors the level of thyroid hormone that circulates around the body and, should it perceive a want, begins producing thyrotropin, which then spurs the thyroid to greater efforts – in the extreme, spurs it to make a goitre. Children who have defective pituitaries are dwarfed for want of growth hormone and cretinous for want of thyroxine.

  But the vast majority of the world’s cases of
cretinism are caused by a simple lack of dietary iodine. The tragedy of six million cretins is that the cure and the prevention of the disease is known, and costs next to nothing: it is simply iodised salt. It was the legislated spread of iodised salt in the early twentieth century that eliminated European goitre and cretinism within a generation, so that today these diseases are little more than folk-memories. Indeed, iodine deficiencies are so utterly forgotten in the developed world that outside medical and scientific circles the term ‘cretin’ exists only as a casual term of abuse. What is more, ‘cretin’ survives where comparable epithets have been justly banished from decent conversation. The word simply has no constituency, no defenders. Are the Taron of Upper Burma cretins? Is their smallness part of the vast and glorious tapestry of human genetic diversity, or are they merely victims of a peculiar form of high-altitude poverty? Were we to hear that there are no longer tribes of little people in the vertiginous gorges of the upper Irrawaddy, should we cheer or lament?

  IL COLTELLO

  Nearly fifteen hundred years ago, while working on a remote Aegean island, Aristotle made an observation that was at once banal, beautiful and chilling. ‘All animals,’ he wrote, ‘if operated on when they are young, become bigger and better looking than their unmutilated fellows; if they be mutilated when full grown, they do not take on any increase of size…As a general rule, mutilated animals grow to a greater length than the unmutilated.’

  By ‘mutilation’ Aristotle meant castration. Hence the banality of his observation that merely repeated facts as well known to any fourth-century Greek farmer as to any modern one. What makes the observation beautiful is that Aristotle thought to write it down. He has taken a barnyard commonplace, that gelded rams, stallions and cockerels are larger than intact animals, and made a scientific generalisation of it – one, moreover, that still stands. What makes these facts so chilling is that when he spoke of animals, Aristotle also meant men.