Читать книгу The Pleasure Principle - Catherine Wilson - Страница 15

Lucretius’s claim that nature had experimented with unsuccessful animal species that lacked the right structure to maintain themselves and reproduce was well known to the 18th- and early-19th-century theorists with whom Darwin was familiar. (One of them was his own grandfather, Erasmus Darwin, the author of a long poem on the origins and evolution of life). The early, hostile reviews of On the Origin of Species all mentioned its relationship with the Lucretian text. One reviewer complained, for example, that there was nothing new in Darwin’s ‘speculative’ cosmogony. ‘It is at least as old,’ he said, ‘as Democritus and Epicurus, and has never been presented with more poetic beauty than by Lucretius.’

Darwin did not attach his own account to Epicureanism, and especially to Lucretius’s version, for obvious reasons. First, Lucretius (and grandfather Darwin) were notorious atheists, and Darwin kept or tried to keep his sceptical views on religion to himself. Second, he had to fend off the charge that his theory of evolution was a poetic fantasy or mere speculation. What, then, was he able to add to (and subtract from) the Epicurean theory that plants and animals evolved ‘by chance’ that changed its status in his mind and eventually in the minds of his early followers? How did Darwinism go beyond speculation to develop into an accepted account of the origin of the various species?

By the time the 19th century rolled around, most naturalists were doubtful that the astonishing number of different species then identified – far too many to have fitted on the Ark – including hundreds of different species of beetles, had been created by twos and on purpose. The true age of the earth had been calculated, and the former existence of the dinosaurs and the giant mammals that had once roamed Europe and Asia was generally known. Two scientific developments transformed the Epicurean theory of the natural origins of plants and animals from a somewhat implausible speculation to a well-founded scientific hypothesis. These were: the cell theory, and the notion of ‘variation’ from generation to generation.

The discovery, based on the microscope, unavailable to ancient philosophers, that all plants and animals were combinations of individual living cells, and that some cells were free-living animals like the amoeba, made it possible to think of the origins of life in terms of the first appearance of a living cell. To imagine, as Epicureanism required, an elephant emerging from a combination of atoms or even from an atomic seed in the earth was far more difficult than imagining a few single cells forming by chance and later joining up into larger cellular units.

Another obstacle for the Epicurean theory was the assumption that animals always gave birth to animals like themselves. This seemed obvious to them. Cows did not give birth to sheep, or blackbirds to swallows. This meant that they had to stick to their theory that the original prototypes of every sort of animal had sprung by chance from the earth. Although they fancied that not all of these animal types had been capable of survival and reproduction, they could not envision the descent of one kind of bird or mammal from an entirely different kind of bird or mammal.

Darwin’s breakthrough occurred when he reflected on the selective breeding farmers had carried on for millennia, choosing from the pack or flock or herd, and breeding together male and female dogs, sheep and cattle with desired characteristics. He knew that within the group, individuals varied in their qualities and that offspring were not exactly like their parents. To the idea of variation, he was able to apply the Epicurean idea of selection – success or failure in living and reproducing.

For Darwin, nature, acting unconsciously, rather than the breeder acting with intention, did the selecting when the resources needed for life were limited and predation was the rule. Animals ate and sometimes killed plants and killed and ate one another. Bacteria, fungi and poisonous plants killed animals. Plants derived nutrition from decomposing animals. Naturalists had long wondered why, if the world was created by a supremely benevolent and skilled craftsman, this was how things worked. They also wondered why trees produced so many useless seeds and short-lived seedlings; why humans produced such an oversupply of ‘spermatic animals’; and why so many children died in infancy. The grim truth was that competition for life was intense. Many individuals of a given species would starve, be eaten or die of accidents before reproducing, or fail to find or attract mates. Darwin argued that the appearance of entirely new species was the result of thousands or millions of generations of variation and selection in changing environments. The temporary stability that the Epicureans had ascribed to the world, which they saw as constantly evolving as the atoms fell into new combinations, was a feature of the individual species as well, and the mortality of the individual person applied to the whole species, whose eventual extinction was similarly inevitable.

Darwin’s contribution, to my mind, was not just to think out how natural selection might work, but to show that it could be considered a lawful process rather than one based entirely on chance. For the constantly repeated accusation against the ancient Epicureans was that the beauty, intricacy and functionality of the many forms of life could not arise from the random motions of atoms. But, in Darwin’s view, the breeder who seeks to improve his or her flock of sheep or hunting dogs, or the pigeon fancier who presents his or her fluffy tailed or brightly feathered specimens to other fanciers, is employing a technology, and wherever a technology is successful, there we expect to find laws of nature. Nature, too, must be employing a technology to create the succession of living forms of the past near 4 billion years.

To be sure, nature is not aiming to improve any individual species or the livestock or biomass of the planet itself. She is not trying to make animals or entire species faster, smarter or more beautiful. In fact, nature is not trying to do anything. But she mercilessly eliminates some members of each species who aren’t keeping up with the others in producing, and in some cases raising to maturity, offspring who will have their own offspring. As a result, the face of living nature changes in ways we can often explain. Species have appeared and disappeared over the eons, and for this to have happened, there must be laws of nature underlying these changes. Chance – or what we think of as chance, namely coincidence – nevertheless plays a role. Many organisms perish, not because they lack strength, speed, cunning or good metabolisms, but just because they were in the wrong place at the wrong time. A good example is the class of dinosaurs that just happened to be inhabiting the earth 65 million years ago when it was hit ‘by chance’ – though fully in accord with the laws of physics – by an asteroid that wiped them all out.

The Lucretian account of the formation of the cosmos and the evolution of animals, and the Judaeo-Christian account of the divine creation of the world, were recognised as rivals from the early medieval period onwards. Their combat has been long and persistent, but also somewhat hidden from view, which is why Darwin receives too much credit for thinking out the basic idea of evolution by natural selection and too little credit for realising that variation was the key that could solve the problem of the origin of new species. The rivalry was not for a long time manifested in open debate because of the severe criminal penalties attached to blasphemy, a capital crime in earlier periods of Judaism, Christianity and Islam, and because of the ubiquity of censorship in many parts of Europe.

Why were ideas about the origins of life so dangerous? It was thought that if too many people began to take seriously accounts of the natural origins of life, they would cease to believe that they were created by and responsible to the God who had created them. If they stopped believing they were responsible to God, they would stop believing that obedience to God’s commands and their rulers was obligatory and that disobedience would be harshly punished. If they stopped believing that obedience was obligatory, they would become libertines, criminals and revolutionaries.

Today, the fear that motivated execution for heretics and resulted in the banning, confiscation and burning of scientific books takes a different form. It is not fear of revolutionary violence that explains the persistence of Creationism and intelligent design theories. Some Creationists would probably like to overthrow their secular governments by force of arms and replace them with theocracies. The fear is rather that if the Epicurean–Darwinian theory is true and intelligent design false, divinities and religious texts are not sources of moral authority, and eternal life is not the reward for faith. In that case, there is no reason to obey the Ten Commandments or all the moral ordinances of one’s own church. Moral anarchy, by which Creationists usually understand homosexuality, adultery, abortion and divorce, and the breakdown of the family and society, will result.

If the divine-command theory of morality were the only option, and if the inescapability of death actually spoiled our lives, worries about the social and psychological effects of accepting evolutionary theory might be justified. But it was Darwin himself, drawing on a long tradition of secular British moral theory as well as his own observations of birds and mammals, who first argued that certain forms of altruism characterised group living animals, contributing to their survival. Conscience, or a moral sense, would inevitably arise, he declared, in any social animal that had developed intelligence comparable to that of a human being.

More recent research on primates and young children has confirmed that the moral sentiment of empathy and the disposition to help others, along with a preference for fairness, are to some extent prefigured in our evolutionary ancestors and wired into us from birth. These endowments can be strengthened and extended, as Darwin saw, through formal learning, or weakened by experience and indoctrination. And despite having no conception whatsoever of the descent of one species from an entirely different one, the ancient Epicureans had a serviceable theory of natural morality that I’ll explore in Chapter 6. They showed how it was possible to live cheerfully and ethically as a mortal.