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4 The (Evolutionary) ‘Reason forEverything’: Certainty

‘There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one … from so simple a beginning endless forms most beautiful and most wonderful have been evolved.’

Charles Darwin, On the Origin of Species (1859)

Charles Darwin, while a theology student at Cambridge University, developed a passion for beetles. ‘Nothing gave me so much pleasure,’ he would write in his autobiography, recalling how, ‘as proof of my zeal’:

One day, on tearing off some old bark I saw two rare beetles and seized one in each hand; then I saw a third and new kind, which I could not bear to lose, so I put the one which I held in my right hand into my mouth. But alas! It ejected some intensely acrid fluid that burnt my tongue so I was forced to spit it out and so it was lost.

Darwin’s zeal for beetles was quite unexceptional, for he was born into the Golden Age of Natural History, when the wonders of nature as revealed by science gripped the public imagination with an extraordinary intensity, while being also the most tangible evidence of a divinely ordained world. ‘The naturalist … sees the beautiful connection that subsists throughout the whole scheme of animated nature,’ observed the editor of the Zoological Journal of London. ‘He traces … the mutual depending that convinces him nothing is made in vain.’

There seemed no limit to the new forms of ‘animated nature’ just waiting to be discovered. In 1771 the famed maritime explorer James Cook had returned from his epic three-year circumnavigation of the world ‘laden with the greatest treasure of natural history that ever was brought into any country at one time’: no fewer than 1,400 new plant species, more than a thousand new species of animals, two hundred fish and assorted molluscs, insects and marine creatures. For his friend the anatomist John Hunter, waiting for him as his ship anchored off Deal harbour, Cook had several unusual specimens to add to his famous collection: a striped polecat from the Cape of Good Hope, part of a giant squid, and a peculiar animal ‘as large as a greyhound, of mouse colour and very swift’, known in the Aboriginal dialect as a ‘kangooroo’.

The discovery of this exhilarating diversity of life extended beyond the living to the long-since extinct. For this, too, was the great period of geological discovery of the antiquity of the earth, the strata of whose rocks revealed fossilised bones and teeth so much larger than any previously encountered as to suggest that vast, fantastical creatures had roamed the surface of the earth millions of years before man.

The immediate fascination of natural history lay in the accurate description of that teeming variety of life, but beyond that there was every reason to suppose that comparing the anatomical structure and the behaviour of living organisms such as the polecat, squid and kangaroo would reveal the long-suspected hidden laws that link all ‘animated nature’ together. The search for those laws stretches back into antiquity, seeking first to explain the ‘vitality’ of the living, the heat, energy and movement that so readily distinguish it from the nonliving, and that depart so promptly at the moment of death. The subtler, yet related, question concerned the nature of ‘form’, those elusive qualities of pattern and order that so clearly distinguish polecat, squid and kangaroo from each other, and the tissues of which they are made – as readily as a grand palace is distinguished from a humble factory, and from the bricks and mortar of which they are constructed. But the elusive ‘form’ of polecat and squid, unlike that of the palace or the factory, has the further extraordinary property of remaining constant throughout their lives, even though the ‘bricks and mortar’ from which they are fashioned are being constantly replaced and renewed. From the first natural historian, Aristotle, onwards, it was presumed that some organising principle, some ‘formative impulse’, must both determine and ensure that constancy of form.

The presiding genius of natural history, Baron Georges Cuvier (1769–1832), director of the Musée d’Histoire Naturelle in Paris, proposed two laws of that ‘formative impulse’, the laws of similarity (homology) and correlation. First, homology. Cuvier inferred from a detailed study of the ten thousand specimens in his collection that the diverse forms of animals each concealed an underlying ‘unity of type’, all being variations on the same ‘blueprint’: the wings of bird and bat, the paddle of a porpoise, the horse’s legs and the human forearm were all constructed from the same bones, adapted to their ‘way of life’ – whether flying or swimming, running or grasping.

His second law, of ‘correlation’, asserted that the various parts of every animal, its skull, limbs, teeth, etc., were all ‘of a piece’, all correlated together, being so fashioned as to fulfil its way of life. Thus a carnivore, such as a lion or hyena, would have limbs strong enough to grasp its victim and muscular enough for hunting, jaws sufficiently powerful and teeth sharp enough to rip its flesh, and so on. ‘Every organised being forms a whole, a unique and perfect system, the parts of which mutually correspond and concur in the same definitive action,’ he wrote.

Cuvier maintained that these laws dictating the harmony of the parts of the ‘unique and perfect system’ were as precise as those of mathematics. He could not specify the biological forces behind them, but they were not merely some theoretical inference. Rather, they could be ‘put to the test’, allowing him, to the astonishment of all, to ‘restore to life’ those fantastical and long-extinct creatures from long ago, reconstructing from the assorted bones and teeth of their fossilised remains a ‘megatherium’, or ‘huge beast’, a creature resembling a giant sloth which would stand on two legs to graze on leaves. ‘Is not Cuvier the great poet of our era?’ enquired the novelist Honoré de Balzac. ‘Our immortal naturalist has reconstructed past worlds from a few bleached bones … discovered a Giant population from the footprints of a mammoth.’