Make your own monster
- Mutants: On the Form, Varieties and Errors of the Human Body by Armand Marie Leroi
HarperCollins, 431 pp, £20.00, May 2004, ISBN 0 00 257113 7
- Jacob’s Ladder: The History of the Human Genome by Henry Gee
Fourth Estate, 272 pp, £20.00, March 2004, ISBN 1 84115 734 1
On 24 August 1848 an advertisement in the Brooklyn Eagle triumphantly announced a performance by ‘the most extraordinary and interesting man in miniature in the known world’. Charles Sherwood Stratton was a perfectly formed 25-inch-tall midget, who weighed only 15 pounds. It had been the idea of the Victorian freak show impresario Phineas Taylor Barnum to present him in the guise of ‘General Tom Thumb’. Before long, the general’s imitations – ‘in full military costume’ – of Napoleon Bonaparte and Frederick the Great, and a varied repertoire including a ‘Scotch song’ and a rendition of the polka, would make him a wealthy man. Following his hugely successful London debut at the Princess’s Theatre four years earlier (the Illustrated London News had described him as ‘a little monster’), he had received three separate invitations to visit Queen Victoria at Buckingham Palace. His unexpected success spawned a host of copycat acts including ‘Anita the Living Doll’, ‘Leonine the Lion Woman’, ‘Chang the Chinese Giant’, ‘Jo-Jo the Dog-Faced Boy’ and John Merrick, the ‘Elephant Man’. But by the turn of the century, the mood of the public had changed and the public display of such ‘human prodigies’ – as they preferred to be called – had become unacceptable in many countries. The profession of ‘museum freak’ was in terminal decline.
Such discontinuous variations on the human form are rare, but we are used to the continuous everyday variations that comprise the full spectrum of the ‘normal’. They leave the basic body plan intact, and are the stuff of evolution by natural selection. The more ‘monstrous’ variations are unlikely to be of direct significance in evolutionary processes, but they do offer invaluable insights into the way animal form is generated.
Unusual characteristics can have environmental causes: the skin of the 19th-century freak show exhibit the ‘Blue Man’ was ‘the colour of a Maltese cat’ as the result of the prolonged administration of silver nitrate for dubious medicinal purposes. Most variation in human form, however, occurs because the genes responsible for every part of our internal and external make-up come in different versions. Each of these arises from a process of random gene modification called mutation, which is largely caused by errors of copying, or the damage done by mutagens such as UV light or chemicals. Occasionally, mutations pass permanently into the genetic record. The frequency with which this happens has itself evolved: if too many errors are introduced into the genome of an organism, its core information will melt away; too few, and there would be insufficient variation for evolution to work with.
In Mutants, Armand Marie Leroi argues that in order to understand how people’s bodies are constructed, biologists need now to focus their attention on the bestiary of human variation, both normal and extreme. As people are not clocks, we cannot simply take them apart and reassemble them to investigate their inner workings, for both practical and ethical reasons. As a result, we must either study nature’s own random ‘experiments’ on human form, as evidenced in ‘normal’ variation and developmental errors, or focus our attention on animals. The latter strategy has proved enormously useful; new technologies enable genes to be inserted or deleted as required, so that their effects on form can be studied. The genomes of flies, worms and fish have been randomly mutated using chemicals or radiation so as to generate bestiaries of bizarre mutants whose detailed mechanics can then be unravelled. Such models are the source of the vast majority of what we currently know about the way animals – including humans – are made.