Darwin's Island (15 page)

If Zacarias Moussaoui, sentenced to life in solitary for his supposed ties to the Twin Towers outrage, were allowed reading material in his soundproofed Colorado cell he might learn something from both Dickens and Darwin about why he feels such hatred for those who do not share his views. As books are not available, he may wish instead to spend his solitary hours in contemplation of the expression of a condemned prisoner as the electricity passes through his head, which is said - in an echo of the great naturalist’s own observations - to be of ungovernable horror.

CHAPTER IV

THE TRIUMPH OF THE WELL-BRED

Charles Darwin was worried about his plans for marriage. Perhaps the whole idea was a mistake because of the time that would be wasted on family life at the expense of science. His diary records how he agonised over the pros and cons of matrimony, and his decision to ‘Marry, marry, marry!’ And marry, in the end, he did.

His spouse was his cousin, Emma Wedgwood. In falling for a relative he stuck to a clan tradition. The Darwins, like many among the Victorian upper crust, had long preferred to share a bed with their kin. Charles’s grandfather Josiah Wedgwood set up home with his third cousin Sarah Wedgwood. Their daughter, Susannah, chose Robert Darwin, Charles’s father. Charles’s uncle - Emma’s father - had nine offspring, four of whom married cousins. The evolutionist’s own marriage was in the end happy, with ten children (and when his wife was in her forties he wrote that ‘Emma has been very neglectful of late for we have not had a child for more than one whole year’). Even so, in Queen Victoria’s fecund days the Darwin-Wedgwood dynasty did less well than most, for among the sixty-two uncles, cousins and aunts (Emma and Charles included) who descended from Josiah, thirty-eight had no progeny that survived to adulthood.

Six years after his wife’s last confinement Darwin began to think about the dangers of inbreeding, in particular as they applied to his own choice of spouse. His concern was picked up from another of his cousins, Francis Galton, the founder of eugenics, who had pointed out the potential dangers of marriage within the clan.

Charles was anxious about his children. His tenth and last, Charles the younger, died while a baby; he was ‘backward in walking & talking, but intelligent and observant’. Henrietta had a digestive illness not unlike that of her father and took to her bed for years, and he feared that his son Leonard was ‘rather slow and backward’ (which did not prevent his later marriage to his own cousin or his acceptance of the Presidency of the Eugenics Society), while Horace had ‘attacks, many times a day, of shuddering & gasping & hysterical sobbing, semi-convulsive movements, with much distress of feeling’. His second daughter, Elizabeth, ‘shivers & makes as many extraordinary grimaces as ever’. George’s problem was an irregular pulse, which hinted at ‘some deep flaw in his constitution’ and, worst of all, his beloved Annie expired at the age of ten, throwing her parents into despair. As he wrote, ‘When we hear it said that a man carries in his constitution the seeds of an inherited disease there is much literal truth in the expression.’ Once he even wrote to a friend that ‘We are a wretched family & ought to be exterminated.’ Might his own illness and that of his sons and daughters be due to his own and his ancestors’ choice of a relative as life-partner? Was inbreeding a universal threat?

His first statement of concern came three years after
The Origin
, as an afterword to his book
On the Various Contrivances by which British and Foreign Orchids are Fertilised by Insects, and on the Good
Effects of Intercrossing
. The last paragraph of that hefty work, most of it devoted to botanical minutiae, ends: ‘Nature thus tells us, in the most emphatic manner, that she abhors perpetual self-fertilisation. This conclusion seems to be of high importance, and perhaps justifies the lengthy details given in this volume. For may we not further infer as probable, in accordance with the belief of the vast majority of the breeders of our domestic productions, that marriage between near relatives is likewise in some way injurious,—that some unknown great good is derived from the union of individuals which have been kept distinct for many generations?’

The idea that children born to related parents might suffer harm was already in the air. The first study of its risks came in 1851 when Sir William Wilde (father of Oscar) found, in work years ahead of its time, an increased incidence of deafness among the progeny of cousins. Sir Arthur Mitchell, the Deputy Commissioner in Lunacy for Scotland, had earlier claimed that in the inbred fishing communities of north-east Scotland the average hat size was six and seven-eighths, a quarter-inch less than that of their more open-minded agricultural neighbours; proof, he thought, of the malign effects of the marriage of kin upon the mental powers.

Sex within the household has a venerable history. The Pharaohs lived through generations of the habit in an attempt to preserve the bloodline of a God. Akhenaten, who lived around 1300 BC, first married his cousin Nefertiti, then a lesser wife, Kiya, and then three of his own daughters by Nefertiti and then (perhaps) his own mother. The story is confused by difficulties with sorting out quite who was who (and one of his supposed wives was in fact male), but incestuous affairs were without doubt common in ancient Egypt. Cleopatra herself may have been the scion of ten generations of brother-sister unions. The practice is condemned in Leviticus, where the Children of Israel were enjoined that ‘After the doings of the land of Egypt, wherein ye dwelt, shall ye not do.’

The belief that the children of cousins are bound to be unfit, and the desire of all rulers to control their citizens’ private lives, still fuels a jaundiced view of the joys of sex within the household. In 2008, a British government minister, in reference to the Pakistani population of Bradford, made the quite unjustified claim that ‘If you have a child with your cousin the likelihood is there will be a genetic problem.’ Many of his fellow citizens share that vague Galtonian sense that inbreeding is harmful. Most of their alarm rests on anecdote rather than on science.

All states are interested in how their subjects behave in the bedroom. For years, England based its marital rules on those of the Church of England, which descend from those of the Israelites, themselves established to put an end to the habits of the Pharaohs. In 1907, after hundreds of hours of parliamentary discussion, the statutes were at last clarified. The new legislation removed absurd anomalies such as the biologically senseless law that forbade a widower to marry his dead wife’s sister but it also firmed up the prohibition against sex with close kin, be it father with daughter, or brother with sister.

Politicians often act on the basis of prejudice. Darwin did not. When faced with a scientific question - about sex or anything else - he set out not to speculate but to discover. To learn more about inbreeding he turned again to plants.
The Effects of Cross and Self-Fertilisation in the Vegetable Kingdom
appeared in 1876. It gives an account of experiments on a wide variety of hermaphrodite plants forced to mate with themselves. His verdict was clear: ‘The first and most important of the conclusions which may be drawn from the observations given in this volume, is that cross-fertilisation is generally beneficial, and self-fertilisation injurious.’ It was ‘as unmistakably plain that innumerable flowers are adapted for cross-fertilisation, as that the teeth and talons of a carnivorous animal are adapted for catching prey’. The exchange of genes between unrelated individuals was the rule and selfing an expensive exception. What was true of plants must, he imagined, apply to animals, men and women included.

Flowering plants have long been known to have sexual habits more inventive than our own. Charles’s grandfather Erasmus’s poem
The Loves of the Plants
is a work of science in two hundred pages of Arcadian verse. Many lines deal with the balance between male and female interests (‘Each wanton beauty, tricked in all her grace, Shakes the bright dew-drops from her blushing face; In gay undress displays her rival charms, And calls her wandering lovers to her arms’ - in other words, this species needs a pollinator). His descendant asked deeper questions in plainer prose. He found that many plants live in a reproductive universe that would have shocked the shepherds of Arcady. They have a system of choice that transcends the familiar preferences of one gender for its opposite. Most retain their original nature as hermaphrodites, with male and female parts in the same flower, but they span the range from obligate self-fertilisers to others that make an absolute demand for pollen from another individual. Many among the latter group have to ensure that they do not accept genes from their close kin, and have imposed additional and refined laws of sexual choice upon their mates.

The cross-fertilisation book was a first step in the scientific study of sex. Fifteen years earlier its author had noted that ‘We do not even in the least know the final cause of sexuality; why new beings should be produced by the union of the two sexual elements, instead of a process of parthenogenesis.’ Not much has changed. We are still not certain how the habit persists in the face of its obvious drawbacks in terms of cost, stress and more - in Dr Johnson’s famous words, its expense damnable, its position ridiculous and its pleasure fleeting. Why mate, when virgin birth ensures that your own genes have a guaranteed chance of survival? Parthenogenesis - virgin birth - guarantees that all the genes of those who indulge in it reach the next generation. It looks like the obvious solution but parthenogenesis remains rare - a few lizards and fish, and about one species of flowering plant in a thousand. For a hermaphrodite, a bout of sex with oneself also ensures that the DNA is not diluted with that of an unrelated individual. For creatures with separate males and females incest - sex with a close relative - is quite effective at keeping genes in the family, but that too is frowned upon.

Plants hint at the answer. Plenty among them have, like men and women, separate sexes. Some - like the strawberry or the dandelion - have gone to the opposite extreme for they are parthenogens and propagate themselves with shoots, roots or broken fragments. The majority of the flowering kinds have taken a lesser step towards asexuality for they are hermaphrodites that bear male and female functions on the same individual.

In spite of the chance they have for sex with themselves some hermaphrodites insist on exchanging genes with a stranger. Others in that situation are, in contrast, happy to self-fertilise and will accept genes from a different flower on the same individual, or evolve flowers with both male and female structures that can fertilise themselves. That pattern marks a real step towards the abandonment of sex.

Animals, too, have often tried to give up that habit. Some, like praying mantises and certain lizards, are true parthenogens, while a few such as snails and worms are hermaphrodites. Others go in for more bizarre forms of close copulation. The habits of mites would astonish any pornographer. A certain parasite of locusts gives birth to two types of male. The first clambers back into his mother and fertilises her. With their help she then produces a second brood, with a few males included - and those males then have sex with their sisters. In another mite, a mother has sex with her grandson, the scion of her own daughter, the daughter herself a child of the mother herself and a son. Other mites confine themselves to brother-sister pairs - but they copulate before they are born.

Darwin saw that, when it comes to sex, plants are more convenient subjects for experiment than animals. Self-pollination in hermaphrodites marks a biological indulgence more extreme than the matings between cousins that so concerned him, or between sons and mothers, fathers and daughters and brothers and sisters. He set out to explore how often it took place, what it did to the health of his subjects and, with luck, to learn a little about the importance of sexual reproduction in general.

Within a few months of starting work as a planned pollinator in the greenhouse at Downe he found that the effects of inbreeding could be dramatic. With the help of a botanical condom - a fine mesh to keep out insects - and a small paintbrush he could himself, like a bee, move male cells to the female parts of a flower and could arrange that the plant received its own genes, or those of another individual.

First, Darwin noted that certain species would self-fertilise, while others refused to do so even when obliged to try. Among those that did, he discovered - somewhat to his alarm - that the habit did damage later generations. His initial experiments were on toadflax, a common yellow-flowered weed. In the wild, outcrossing was the rule. In the greenhouse, he could force his subjects to self, and soon found a large, and unexpected, effect upon the next generation. The progeny of such crosses were smaller and less vigorous than were those of plants allowed to mate with another. At first he supposed that his inbred offspring were weakly because of some disease, or because they were grown in unsuitable soil. That was not so, for however well they were treated they stayed feeble. Darwin ran through a variety of species - carnations, tobacco, peas, monkey-flowers, morning glory, foxgloves and many other garden and wild flowers. With statistical help from Francis Galton he discovered that, almost without exception, those grown from crossed seed were taller, healthier and more productive than were those from self-fertilised. Some experiments went on for several generations, and the effects of sex with a relative got worse with time. The inbreds suffered most of all when life was hard: when they were crowded, had to compete with their outcrossed kin or were moved from the greenhouse to the rigours of the open air. The malign influence of selfing applied almost as much to species that went in for it in nature as to those that almost never did so.