Darwin's Island Read online

  Some of his travels were in search of science, but many were a quest for health. He became chronically ill very soon after his return from the Beagle trip and his heavy use of snuff and tobacco did nothing to improve his well-being. Darwin visited spas in Great Malvern, in Guildford and in Ilkley (where he received the first copy of The Origin). His later years were marked by a series of bizarre attempts to remedy his feeble state (even if he did write that illness, ‘though it has annihilated several years of my life, has saved me from the distractions of society and amusement’). The main symptom was vomiting, often brought on by stress, with the rushed last chapter of The Origin sparking off a severe episode that caused great prostration of mind and body. So severe were the attacks that he declined some invitations to stay in friends’ houses on the grounds that ‘my retching is apt to be extremely loud’.

  He tried Condy’s Ozonised Fluid, ‘enormous quantities of chalk, magnesia & carb of ammonia’, and rubber bags filled with ice and worn next to the spine. Nothing worked (although he learned to play billiards at one of the establishments and became a devotee of the pastime, which helped him to relax and, as he said, ‘drives the horrid species out of my head’). The author of The Origin was a victim of the Victorian ‘Demon of Dyspepsia’ and was joined in that unhappy throng by Thomas Carlyle, George Eliot, Charles Dickens, Florence Nightingale and the evolutionists T. H. Huxley, Alfred Russel Wallace and Herbert Spencer, together with his own brother Erasmus. Their troubles funded several pharmaceutical fortunes (including that of Henry Wellcome, which later helped pay for that Darwinian triumph, the sequence of human DNA). What his condition might have been is not known: a supposed conflict between Christian belief and rationalism, or a parasite picked up in Brazil or even, some say, the obsessive swallowing of air. He was diagnosed as having ‘waterbrash’ - heartburn, in modern parlance, the reflux of acid from the stomach - which can result from an ulcer. Dyspepsia’s nausea, depression and lassitude are, we know today, caused by a bacterium. The bug that swept through Victoria’s intellectuals might now be cured with a simple pill.

  Later in life, in part because of his health, the paterfamilias of Down House spent longer and longer periods without leaving home. He fed his household with fifty-three distinct varieties of gooseberries and three of cabbage. In his garden he carried out many experiments, helped by William Brooke, his ‘gloomy gardener’ (who was seen to laugh just once, when a boomerang broke a cucumber frame). The naturalist’s tale ends, in the tradition of the classics, with the hero’s death and his desire to join his beloved earthworms in the ‘sweetest place on Earth’, the village churchyard at Downe - a wish frustrated by fame, the establishment and the Abbey.

  Darwin’s Island retraces some of Darwin’s steps and moves his discoveries forward by a century and more. It will, I hope, help bring his less well-known work into the third millennium. Several people have helped in the preparation of this book. David Leibel, Michael Morgan, Kay Taylor and Anna Trench made helpful comments on parts of it. I thank them for their help.

  Three of my earlier volumes - on coral reefs, on the nature of maleness and on the theory of evolution itself - pay homage to the founder of the science of life, and each is an attempt to update his ideas for the modern age. There could be no better way to honour the most famous of all biologists at this time of concentrated attention on his history than to give his less celebrated works the exposure they deserve. For Charles Darwin, the five Beagle years that became part of Britain’s intellectual legacy led to four decades of intense labour within the confines of his native land. In that modest group of islands he underwent a second great voyage: not of the body but of the mind. This book traces that journey from its beginning to its end.

  CHAPTER I

  THE QUEEN’S ORANG-UTAN

  In 1842 Queen Victoria went to London Zoo. She was less than amused: ‘The Orang Outang is too wonderful … he is frightfully, and painfully, and disagreeably human.’ The animal was not a male but a female called Jenny and Charles Darwin had, some years earlier, visited its mother. He too spotted the resemblance between the apes on either side of the bars. The young biologist scribbled in his notebook that ‘Man in his arrogance thinks himself a great work. More humble and I believe true to consider him created from animals.’ Seventeen years after Victoria’s visit, in 1859, he published the theory that proved the Queen’s kinship, and his own, to Jenny, to every inmate of the Zoological Gardens and to all the inhabitants of the Earth.

  The Origin of Species caused uproar among the Empress of India’s subjects. Her Chancellor, Benjamin Disraeli, asked famously: ‘Is man an ape or an angel? My Lord, I am on the side of the angels. I repudiate with indignation and abhorrence these new fangled theories.’ Many of his fellow citizens agreed. Even so, the notion at once entered public discourse (and Punch devoted its 1861 Christmas annual to gorilla-like humans and their opposites). In time, and with some reluctance, the notion that every Briton, high or low, shared descent with the rest of the world was accepted. A quarter of a century on, W. S. Gilbert penned the deathless line that ‘Darwinian man, though well behaved, at best is only a monkey shaved’ and the idea of Homo sapiens as a depilated ape became part of popular culture, where it belongs. Victoria herself congratulated one of her daughters, the crown princess of Prussia, for turning to The Origin: ‘How many interesting, difficult books you read. It would and will please beloved Papa.’

  As the Queen had noticed, the physical similarity of men to apes is clear. In 1859, Charles Darwin came up with the reason why. A certain caution was needed to promote the idea that what had made animals had also produced men and women, and he waited for twelve years before he expanded on the subject. The Descent of Man describes how - and why - Homo sapiens shares its nature with other primates. The book uses our own species as an exemplar of evolution.

  To the founder of modern biology, man obeyed the same evolutionary rules as all his kin and shared much of his physical being with them; as the book says, in its final paragraph, he still bears ‘the indelible stamp of his lowly origin’. In moral terms Homo sapiens was something more: ‘… of all the differences between man and the lower animals, the moral sense or conscience is by far the most important. This sense … is summed up in that short but imperious word “ought,” so full of high significance. It is the most noble of all the attributes of man, leading him without a moment’s hesitation to risk his life for that of a fellow-creature.’ No ape understands the meaning of ‘ought’, a word pregnant with notions quite alien to every species apart from one. Even so, despite that essential and uniquely human attribute, every ape - and we are among them - is, like every other creature, the product of a common biological mechanism.

  The logic of evolution is simple. There exists, within all plants and animals, variation passed from one generation to the next. More individuals are born than can live or breed. As a result, there develops a struggle to stay alive and to find a mate. In that battle, those who bear certain variants prevail over others less well endowed. Such inherited differences in the ability to transmit genes - natural selection, as Darwin called it - mean that the advantageous forms become more common as the generations succeed each other. In time, as new versions accumulate, a lineage may change so much that it can no longer exchange genes with those that were once its kin. A new species is born.

  Natural selection is a factory that makes almost impossible things. It manufactures what seems like design with no need for a designer. Evolution builds complicated organs like the eye, the ear or the elbow by piecing together favoured variants as they arise. Almost as an afterthought, it generates new forms of life.

  Its tale as told in The Origin of Species turns on the efforts of farmers as they develop new breeds from old, on changes in wild creatures exposed to the rigours of nature and the demands of the opposite sex, on the tendency of isolated places to evolve unique forms, and on the silent words of the fossils that tell of a planet as it was before evolution moved on. Its pages speak
of the embryo as a key to the past and of how structures no longer of value and others that appear almost too perfect are each testimony of the power of natural selection. The geography of life, on islands, continents and mountains, is also evidence of the common descent of mushrooms, mice and men. Most of all, life’s diversity can be arranged into a series of groups arranged within groups, of ever-decreasing affinity, as a strong hint that they split apart from each other longer and longer ago.

  The Descent of Man uses that logic to disentangle the history of a single species. Unique as it might think itself, Homo sapiens is animal like all others. The book’s famous last sentence reads, in full: ‘I have given the evidence to the best of my ability: and we must acknowledge, as it seems to me, that man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his god-like intellect which has penetrated into the movements and constitution of the solar system - with all these exalted powers - Man still bears in his bodily frame the indelible stamp of his lowly origin.’

  In 1871 - and even in 1971 - the evidence for that final and provocative statement was weak indeed. Now, everything has changed. The entire evolutionary case can be made in terms of ourselves and our relatives; of apes and monkeys, of chimps and gorillas, and of men and women. Our new ability to look at genes, cells, tissues and organs in exquisite detail means that we know more about the human past than about that of any other species. Evolution is best viewed through our own eyes; and not just because we are all interested in where we came from but because advances in science mean that Homo sapiens has become the embodiment of every evolutionary idea. Darwin’s theory has not altered much in the century and a half since it was proposed. The technology used to study it has, on the other hand, been transformed.

  Technical as they have become, the tools used today to examine the past would have been familiar in their nature, if not in their details, to biologists of the nineteenth century. Charles Darwin was, among his many talents, a proficient anatomist. He used changes in the physical structure of pigeons, pigs and people as evidence for his theory. The first chapter of The Descent of Man is a somewhat ponderous account of the differences between the bones and bodies of men and apes. Dissection, once at the centre of biology (and biologists of a certain age still flinch at the smell of formalin), not long ago appeared antiquated, but now it looks very modern. Molecular biology is no more than comparative anatomy plus a mountain of cash. Its chemical scalpels cut up creatures into thousands of millions of individual letters of DNA code. Those who wield them have shown beyond all doubt the truth behind Queen Victoria’s fear that the bodily frame of Jenny the orang-utan was proof of the common ancestry of humans with apes and with far more.

  The Human Genome Project - the scheme to read off our own DNA sequence - set the seal on an enterprise which began in the sixteenth century when Vesalius opened the heart and discovered that it had four chambers rather than the three insisted on by the Greeks. Its completion was announced in 2000 and again in 2003, 2006 and 2008 (and some parts of the double helix still remain unread). A science that had been in its infancy a mere description of bones and muscles became an adolescent when The Origin of Species showed how shared structure was evidence of common descent. It has at last matured. The anatomy of DNA has become the key to the history of life.

  In a glass-fronted cabinet at University College London resides the stuffed body of the eighteenth-century philosopher Jeremy Bentham, the ‘greatest good for the greatest number’ man. His Auto-Icon, as he called it, was an attempt at a memorial that would cost less than the showy shrines then fashionable. Bentham was convinced that his idea would catch on. Two centuries later, it did. James Watson - the surviving half of the duo who unwound the double helix - was presented with his own auto-icon, a compact disc of his entire DNA sequence, which he can, if he wishes, display for public edification in a small plastic case.

  Watson’s essence is coded into a tangled mass of intricate chemistry. The egg that made him contained two metres of DNA and each of the billions of cells that descend from it as his body grows and ages has a copy. Each of those molecular sentences is written in three thousand two hundred million letters, the four bases of the familiar genetic code. Twenty years ago, when the scheme to read the whole lot off was proposed, it took months to decipher the number of letters found in this paragraph. The molecule was sliced into random bits, each was read from end to end and the whole genome stitched together with a search for places where the fragments overlap. Such methods are antique. Today’s machines pick up flashes of light from molecules tagged with fluorescent dyes, each base with its own colour, and squeezed one at a time through tiny pores. It takes no more than a few hours to read off a piece as long as this entire book, which itself contains less than one part in several thousand of the whole content of the human genome. Soon it will become possible to sequence single molecules rather than multiple copies, as is now necessary, and enthusiasts speak of machines that will read off a million DNA bases a second.

  The first human sequence cost up to a billion dollars and Watson’s version was auctioned off for a million. In 2008 the Knome Corporation offered to read off the DNA of anybody with a spare $350,000. In fact, the whole lot can now be done for a fraction of that sum. Within five years the price will drop to a few thousand dollars per genome and it will become possible to decipher the DNA of any creature at nominal cost. The web of kinship that binds life together will then be revealed in all its details.

  The raw material of evolution is, in its physical structure as an intertwined helix, simple or even elegant, but in its biology is entirely the opposite. In its details DNA is, frankly, a mess, for natural selection has been forced to build upon what it already has. Life did not emerge from engineering, but from expedience. The Darwinian machine has no strategy and can never look forward. Its tactics are based on the moment, and the genomes it makes, like the creatures they code for, are the products of a set of short-term fixes. James Watson’s molecule is marked by redundancy, decay and the scars of battles long gone. Genes - like cells, guts and brains - work, but only just.

  Human DNA contains long stretches that appear to be useless and numerous sections that are mirror-images of each other. Repetition is everywhere: of particular genes into families that carry out similar tasks and of multiplied lengths of material that seems redundant. The remnants of viruses make up almost half the total and the remainder is littered by the decayed hulks of ancient and once functional structures. All but one part in fifty of the genome was, as a result, once (mistakenly) dismissed as biological garbage.

  The genes themselves have become blurred and ambiguous as we learn more. There are far fewer than expected when the genome project was proposed - just over twenty thousand rather than the multitude then assumed to be essential. Some overlap with each other or say different things when read in opposite directions or when active in different tissues. Many contain inserted sequences of DNA that looks as if they have no function (although some of the supposed junk does a useful job while other sections cause disease should they wake up and shift position). Plenty of questions remain. How important is the part - often a small part - of each gene that codes for proteins compared with the on and off switches, the accelerators and brakes, and the rest of the control machinery? We do not know.

  Even the size of the package makes little sense. A chicken has slightly less DNA than does a Nobel laureate but half its genes are identical, or almost so, to our own - evidence, given that we last shared an ancestor three hundred million years ago, of how conservative evolution can be. A tiny plant called Arabidopsis, a relative of the Brussels sprout, has more genes than either. All this says more about how hard it can be to define what a gene actually is than about the talents of sprout versus sentient being.

  Eight decades passed between Vesalius’ dissection of the heart and the discovery of the circulation of the blood. The ge
nome is now in that transitional period. DNA’s nuts and bolts (and even some of its bells and whistles) have been dismantled, but most of those who work on it still study structure without much insight into function. William Harvey (the circulation man) saw the heart as a mere pump, and understood nothing of its exquisite system of control. Genes are much the same. Each is linked into a network with others and responds to messages from both within and outside the cell. The path from instruction to product is a labyrinth, rather than a straight line. The proteins that pour from the cell’s biological factories are not simple blocks that slot together but are folded, spliced, cut, or fused into new mixtures in a way that depends on local conditions almost as much as upon their own structure. Diseases as different as diabetes and prostate cancer may arise from damage in the same segment of DNA, while others such as breast cancer emerge from errors in several different genes. Most of the double helix is switched off the majority of the time, African genes are, on average, more active than are those of Europeans and life has begun to look far more complicated than any molecular biologist had feared.