GROWING BONES
A newly born infant has a skeleton of filigree fineness and intricacy, a skull as soft as a sheet of cardboard but scarcely as thick, and femurs as thin as pencils. By the time the child is an adult all this will have changed. The femur will have the diameter of a hockey stick, and will be able to resist the impact of one as well, at least most of the time. The skull will be as thick as a soup plate and capable of protecting the brain even when its owner is engaged in a game of rugby or the scarcely less curious customs of the Australian Aborigines who ritually beat each other’s skulls with thick branches.
What makes bones grow to the size that they do? In 1930 a young American scientist, Victor Chandler Twitty, tackled this question in a very direct way. Taking a cue from the German Entwicklungsmechanik, Twitty chose to study two species of salamanders: tiger salamanders and spotted salamanders. Closely related, they differ in one notable respect: tiger salamanders are about twice as big as spotteds. The experiment he carried out on them was of such elegance, simplicity and daring that seventy years later it can still be found in textbooks.
Twitty began by cutting the legs off his salamanders. The Italian scientist Lazzaro Spallanzani of Scandiano had discovered in 1768 that salamanders can regrow, should they need to, their legs and tails. Since then, thousands of the creatures have lost their legs to science. One luckless animal had a leg amputated twenty times – and grew it back each time. It is sometimes facetiously remarked among scientists that happiness is finding an experiment that works and doing it over and over again. Twitty, however, was more ingenious. As the stumps of his salamanders healed, and as their tissues reorganised into limb-buds, he once again put them to the knife. He then took the severed limb-buds of each species and grafted them onto the stumps of the other.
The question was, how big would the foreign limbs grow? There were, Twitty reasoned, two possibilities. As the grafted buds grew into legs, they might take on the properties of their host, or they might retain their own. If the first, then a spotted salamander limb-bud grafted onto a tiger salamander should grow into a hefty, tiger salamander-sized leg. Alternatively, the spotted salamander limb-bud might simply grow into the small leg that it usually does. The result would be tiger salamanders with three large legs and one tiny grafted one, and spotted salamanders with three tiny legs and one large grafted one – in short, lopsided salamanders.
Twitty expected that the foreign legs would grow as large as the host salamanders’ normal legs. By the 1930s it was known that hormones have an immense influence over human growth. One, produced by the pituitary gland, had even been dubbed ‘growth hormone’, and clinicians spoke of people with an excess or deficiency of this hormone as ‘pituitary’ giants and dwarfs. If tiger salamanders were larger than spotted salamanders, it was surely because they had more growth hormone (or something like it) than their smaller relatives. Foreign limbs should respond to the hormone levels of their hosts no less than ordinary limbs and should become accordingly large or small. The control of growth would be, in a sense, global – a matter of tissues being dictated to by a single set of instructions that circulate throughout the whole body.
There is no doubt that hormones do play a role – a vital role – in how large salamanders, people, and probably all animals become. But the beauty of Twitty’s experiment is that it showed that, however important hormones are, they are not responsible for the difference between large and small salamanders. Against expectation, his salamanders proved lopsided. It seemed as if the grafted limbs, in some ineffably mysterious way, simply knew what size they should be regardless of what they were attached to. It was an experiment that showed the primacy of the local over the global, and that each salamander leg contains within itself the makings of its own fate.
The reward of these experiments was, for Twitty, enduring fame of a modest sort. More immediately, in 1931 he got to go to Berlin. He went to work at the laboratory of Otto Mangold, husband of Hilda Pröscholdt of organiser fame, at the Kaiser Wilhelm Institute. There he met some of the great biologists of the day: Hans Spemann, Richard Goldschmidt and Viktor Hamburger, who together had made Germany pre-eminent in developmental biology. Neither Twitty’s research at the Kaiser Wilhelm, nor his later career as a much-loved Stanford professor, are of particular interest to us, but the time and the country are. Four hundred kilometres to the south, in Munich, another young scientist with similar research interests, but of a rather different stamp, had just started medical school. This was Josef Mengele.
AUSCHWITZ, 1944
The man whose name forever casts a shadow over the study of human genetics came from a well-to-do family of Bavarian industrialists. Handsome, smooth and intelligent, he refused to join the family firm and instead studied medicine and philosophy at Munich University. He was ambitious, and desired ardently to make a name for himself as a scientist, the first of his family. By the mid-1930s he had moved to Frankfurt where he became the protégé of Otamar Freiherr von Verschuer, head of another Kaiser Wilhelm Institute, but one devoted to anthropology. The dissertation that Mengele wrote there in 1935 reflects the prevailing obsession of German anthropology with racial classification and involved the measurement of hundreds of jawbones in a search for racial differences. Two later papers are about the inheritance of certain disorders such as cleft palate. All these works are dry, factual, and rather dull. They contain no hint of the young scientist’s future career.
Mengele arrived at Auschwitz on 30 May 1943. He had been urged to go there by his mentor, von Verschuer, and it was von Verschuer too who had urged Mengele to take advantage of the, as it was put to him, ‘extraordinary research opportunities’ he would find there. By the time he arrived at the concentration camp, it contained just over a hundred thousand prisoners and the killing-machine was fully engaged.
Mengele was only one of many medical staff at Auschwitz-Birkenau, and he was not particularly senior. But after the war, it would be Mengele whom the survivors would remember. They would remember him for his physical beauty, the exquisiteness of his uniform, his charm, and his smile. They would remember him for the unfathomable quality of his personality: he was a man who could speak kindly to a child and then send it to a gas chamber. They would remember him because he was ubiquitous, and also because he was often the first German officer they saw. As the prisoners stepped from the cattle-cars onto the platform at Birkenau, they would hear him shout ‘Links‘ or ‘Rechts‘. ‘Left’ and they would die immediately, ‘Right’ and they were spared, at least for a time.
Among those spared was a thirty-year-old Jewish woman named Elizabeth Ovitz. She and her siblings arrived at Auschwitz-Birkenau on the night of 18 May 1944. They were brought there in a cattle-car containing eighty-four other people. Weak and disoriented from the journey, the Ovitzes stood on the Birkenau railway platform under the glare of arc lights. Elizabeth asked a prisoner, a Jewish engineer from Vienna, where they were. He replied, ‘This is the grave of Israel,’ and pointed to the smokestacks that towered over the camp. Forty-three years later she would write: ‘Now we realised everything that we knew before, and had tried to erase from our consciousness, would actually come about.’ Elizabeth and her siblings, twelve in all, were herded to one side. It was then that they met Mengele. Surveying them with fascination he declared: ‘Now I will have work for the next twenty years; now science will have an interesting subject to consider.’