The Day the Universe Changed - James Burke [127]
As for the absence of man from the earlier fossil levels, clearly in the case of such a vast time-scale it was likely that he had not been present at the earliest times. Further proof of Lyell’s views lay in the difference between the flora and fauna on both sides of the Andes. In the Pacific Darwin also saw proof of continuing processes when an island rose out of the sea during an earthquake.
Soon after his return to England, Darwin found the answer to the remaining puzzle. If Lyell were right and the processes were gradual and uniform instead of frequent and catastrophic, the number of extinct species still had to be accounted for. In some cases climatic change might have provided the necessary conditions, but it was not clear why some species had been successful while others had died out.
Darwin discovered the answer in September 1838, in a book called Essay on the Principle of Population by Thomas Robert Malthus, a clergyman and economist. Writing in 1798 at a time when the wars with France had caused the price of grain to rise very high, bringing the last great famine to Britain, Malthus was influenced by the French theorist Turgot who believed that investment in agriculture could only bring diminishing returns. In his essay Malthus set out the argument that the best to be expected from agriculture would be arithmetical increase of crops. Production would increase as a multiple of 2, then of 3, 4, 5, 6, and so on. This increase would provide enough food to encourage reproduction and in consequence the population would grow. However, population growth would be not arithmetical but geometrical, that is by multiples of 2, 4, 8, 16, and so on. According to Malthus the only way of checking this rise in population during times of plenty would be to take social and moral decisions such as late marriage and contraception. Without such restraint the population must inevitably rise faster than the food supply.
Malthus seemed to find support for his views in the figures of the first census of 1801, which showed an enormous increase in the population during the previous years. Not long before Darwin read the essay, Malthus had been successful in getting the Prime Minister, William Pitt, to withdraw his bill providing for supplementary workhouse grants to be paid to poor agricultural workers. Malthus’argument was that if the workhouse were made too attractive a prospect, large families would have less fear of starvation and the birth rate would rise. The increase in population would need extra poor relief, which in turn would encourage more breeding, and so on.
Darwin adopted Malthus’theory that population is limited by subsistence and, in the absence of moral restraint, will increase, and that as a result survival will be a matter of constant competition for limited resources. The key sentence for Darwin was: ‘It may safely be pronounced therefore that the population, when unchecked, goes on doubling itself every twenty-five years, or increases in a geometrical ratio.’On this model, Darwin wrote:
A struggle for existence inevitably follows from the high rate at which all organic beings tend to increase. It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms; for in this case there can be no artificial increase of food, and no prudential restraint from 258 marriage.
Nature, red in tooth and claw. Victory in the constant struggle for survival goes to the strongest.
This, then, was evidence in the modern world