Mutants (22 page)

N
EGRITOS
. P
ORT
B
LAIR
, A
NDAMAN
I
SLANDS C
.1869–80.

Theories about the cause of pygmy shortness long antedate sure knowledge of their existence. The
Geranomachia
was a favourite theme of Attic artists, who knew only two things
about pygmies: that they were short and that they did not like cranes. A red-figure rhyton from the Classical period therefore shows an achondroplastic dwarf clubbing a bird. The diagnosis of achondroplasia is unambiguous – the limbs of the bird’s assailant are short and bowed, yet his torso, head and genitals are of normal size. Pompeii has yielded a fresco, now in the Naples Museum, in which bands of pygmies hunt crocodiles while others are consumed by hippos, and yet others copulate energetically on the banks of the Nile. These Roman pygmies are not deformed, but rather have the large heads and spindly limbs of emaciated three- or four-year-old children. The oddness of these images is perfectly excusable, since none of the artists had ever seen a pygmy; they were depicting the fabulous by appealing to the familiar. More surprisingly, as recently as 1960 a leading anthropologist and expert on pygmies asserted that they are small because of an achondroplastic mutation. Little is known about what makes pygmies short, but this is certainly wrong.

That pygmy proportions are not the result of any known pathology is clear from the skeleton collected by Emin Pasha. It shows that pygmies have limbs that are beautifully proportioned, but that differ from those of taller people in subtle ways. The action of natural selection over the course of tens of thousands of years has made a form more gently sculpted than the dramatic mutations familiar to the clinical geneticist. Studies of children fathered by tall African farmers on pygmy women suggest that pygmy smallness is probably not due to a single mutation, since the children have a height intermediate to that of the parents. So several genes are probably responsible for pygmy
shortness. We do not know what these genes are, but we do have some idea of what they do. Careful measurements of pygmies (and thousands of them have been measured) show that compared to taller people, pygmies have relatively short legs but relatively long arms. They also have heads and teeth that are relatively large for their torsos. They have, in fact, not only the height, but also the linear proportions of an eleven-year-old British child.

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.

T
HIBAUT
-F
RANCESCO AND
C
HAIR
-A
LLAH
-L
UIGI
, V
ERONA C
.1874. F
ROM
A
RMAND DE
Q
UATREFAGES
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 frontiers 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.