The Invention of Nature (35 page)

Darwin’s finches from the Galapagos Islands (Illustration Credit 17.3)

The implications were revolutionary. If God had created plants and animals in the first place, did the concept of evolving species imply that he had made initial mistakes? Similarly, if species became extinct and God continuously made new ones, did this mean that he constantly changed his mind? It was a terrifying thought for many scientists. The discussion about the possible transmutation of species had been rumbling on for a while. Darwin’s grandfather Erasmus had already written about it in his book Zoomania, as had Jean-Baptiste Lamarck, Humboldt’s old acquaintance from the natural history museum in the Jardin des Plantes in Paris.

In the first decade of the nineteenth century Lamarck had declared that, influenced by their environment, organisms might change along a progressive trajectory. In 1830, the year before Darwin set sail on the Beagle, the battle between the ideas of mutable species versus fixed species had turned into a vicious public row at the Académie des Sciences in Paris.5 Humboldt had attended the fierce discussions at the Académie during a visit to Paris from Berlin, whispering a running commentary of disparaging remarks about the fixed species arguments to the scientists sitting next to him. Already in Views of Nature, more than two decades previously, Humboldt had written about the ‘gradual transformations of species’.

Darwin was also convinced that the idea of fixed species was wrong. Everything was in flux, or, as Humboldt said, if the earth was changing, if land and sea were moving, if temperatures were cooling or rising – then all organisms ‘must also have been subjected to various alterations’. If the environment influenced the development of organisms, then scientists needed to investigate climates and habitats more closely. Therefore, the focus of Darwin’s new thinking became the distribution of organisms across the globe, which was Humboldt’s specialty – at least for the world of plants. Plant geography, Darwin said, was a ‘keystone of the laws of creation’.

As Humboldt had compared plant families on different continents and from different climates, he had discovered vegetation zones. He had seen how similar environments often contained closely related plants, even when divided by oceans or mountain ranges. Yet this was confusing too because despite these analogies across continents, a similar climate didn’t always, or even necessarily, produce similar plants or animals.

As Darwin read Personal Narrative, he highlighted many of these examples.6 Why was it, Humboldt had asked, that the birds in India were less colourful than those in South America, or why was the tiger only found in Asia? Why were the great crocodiles so plentiful in the Lower Orinoco but absent from the Upper Orinoco? Darwin was fascinated by these examples and often added his own comments in the margins of his copy of Personal Narrative: ‘like Patagonia’, ‘in Paraguay’, ‘like Guanaco’ or sometimes just an affirmative ‘yes’ or ‘!’.

Scientists like Charles Lyell explained that these related plants that were found across huge distances had been produced in several centres of creations. God had made these similar species in tandem at the same time and in different regions, in a series of so-called ‘multiple creations’. Darwin disagreed and began to underpin his ideas with arguments on migration and distribution, using Humboldt’s Personal Narrative as one of his sources. He underlined, commented and devised his own indexes for Humboldt’s books as well as writing reminders to himself on sheets that he glued on to the endpapers – ‘When studying Geograph of Canary Botany look at this part’ – or jotting down in his notebook ‘Study Humboldt’ and ‘consult the VI Vol. of Pers. Narra.’ He also commented, ‘Nothing respect to Species Theory’, when the sixth volume did not yield the necessary examples.

Species migration became a main pillar of Darwin’s evolutionary theory. How did these related species move across the globe? To find an answer Darwin conducted many experiments, for example testing the survival rate of seeds in salt water to investigate the possibility of plants having crossed the ocean. When Humboldt noted that an oak that grew on the slope of Pico del Teide in Tenerife was similar to one in Tibet, Darwin queried ‘how transported was acorn … Pidgeons bring grain to Norfolk – Maize to Artic’. When Darwin read Humboldt’s account of rodents opening the hard-shelled Brazil nuts and how monkeys, parrots, squirrels and macaws fought over the seeds, Darwin scribbled in the margin: ‘so dispersed’.

Where Humboldt was inclined to believe that the conundrum of the movement of plants could not be solved, Darwin took up the challenge. The science of plant and animal geography, Humboldt wrote, was not about ‘the investigation of the origin of beings’. What exactly Darwin thought when he underlined this statement in his copy of Personal Narrative we don’t know, but it was clear that he had set out to do precisely that – he was going to find out about the origin of species.

Darwin began to think about common ancestry, another subject for which Humboldt provided plenty of examples. The crocodiles of the Orinoco were gigantic versions of European lizards, Humboldt said, while ‘the shape of our little house pet is repeated on a larger scale’ in the tiger and jaguar. But why did species change? What triggered their mutability? As one of the main proponents for the transmutation theory, the French scientist Lamarck had argued that the environment had changed, for example, a limb into a wing, but Darwin believed this to be ‘veritable rubbish’.

Darwin found the answer in the concept of natural selection. In autumn 1838 he studied a book that helped him shape these ideas: English economist Thomas Malthus’s Essay on the Principle of Population. Darwin read Malthus’s gloomy prediction that human populations would grow faster than their food supply unless ‘checks’ such as war, starvation and epidemics controlled the numbers. The survival of a species, Malthus had written, was rooted in an overproduction of offspring – something that Humboldt had also described in Personal Narrative when discussing the enormous amount of eggs that turtles laid in order to survive. Seeds, eggs and spawn were produced in huge quantities but only a tiny fraction grew to maturity. There is no doubt that Malthus provided what Darwin called ‘a theory by which to work’, but the seeds of this theory had been sown much earlier when he had read Humboldt’s work.

Humboldt discussed how plants and animals ‘limit each other’s numbers’ as well as noting their ‘long continued contest’ for space and nourishment. It was a relentless battle. The animals that he had encountered in the jungle ‘fear each other’, Humboldt observed, ‘benignity is seldom found in alliance with strength’ – an idea that would become essential to Darwin’s concept of natural selection.

At the Orinoco Humboldt had commented on the population dynamics of capybaras, the world’s largest rodents. As he had paddled along the river, he had observed how rapidly the capybaras reproduced, but also how jaguars chased them on land and how crocodiles devoured them in the water. Without these ‘two powerful enemies’, Humboldt had noted, capybara numbers would have exploded. He had also recorded how jaguars pursued tapirs and that monkeys screamed ‘affrighted at this struggle’.

‘What hourly carnage in the magnificent calm picture of Tropical forests,’ Darwin scribbled in the margins. ‘To show how animals prey on each other,’ he noted, ‘what a “positive” check.’ Here, written in pencil in the margins of Humboldt’s fifth volume of Personal Narrative, Darwin recorded for the first time his ‘theory by which to work’.

In September 1838 Darwin wrote in his notebook that all plants and animals ‘are bound together by a web of complex relations’. This was Humboldt’s web of life – but Darwin would take this a step further and turn it into a tree of life from which all organisms stem, with the branches leading to extinct and to new species. By 1839 Darwin had formulated most of the basic ideas that underpinned his theory of evolution, but he continued to work on it for twenty more years before he published the Origin of Species in November 1859.

Fittingly, even the last paragraph of the Origin of Species was inspired by a similar section in Personal Narrative, highlighted by Darwin in his own copy. Darwin took Humboldt’s evocative description of thickets teeming with birds, insects and other animals7 and turned it into his famous entangled bank metaphor:

It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us.

Darwin was standing on Humboldt’s shoulders.

1 Worried about the little space in the poop cabin, Darwin had asked the captain before the departure if he was allowed to take his own copy of Personal Narrative. ‘You are of course welcome to take your Humboldt,’ the captain assured him.

2 The Beagle also carried a missionary and three Fuegians whom FitzRoy had taken hostage on his previous voyage and brought to England. They were now to return home to Tierra del Fuego where FitzRoy hoped that they would convert their fellow Fuegians to Christianity once he had set up a missionary settlement there.

3 The entire description reads very similarly. Humboldt’s ‘the earth is shaken on its old foundations, which we had deemed so stable’, becomes in Darwin’s journal: ‘the world, the very emblem of all that is solid, moves beneath our feet.’ Humboldt wrote, ‘we mistrust for the first time a soil, on which we had so long placed our feet with confidence,’ and Darwin followed with: ‘one second of time conveys to the mind a strange idea of insecurity.’

4 Darwin also secured government funding to publish Zoology of the Voyage of H.M.S. Beagle – to ‘resemble on a humbler scale’ Humboldt’s magnificent zoological publications, he said.

5 In the corner of the fixed species argument were those who believed that animals and plants became extinct and that God regularly created new ones. Their opponents argued that there was an underlying unity or a blueprint from which different species developed as they adapted to their particular environment – variants of what Goethe had called ‘urform’. They argued that the wings of a bat or the paddle of a porpoise, for example, were all variations of forelimbs.

6 There are several hundred references to Humboldt in Darwin’s manuscripts – ranging from Darwin’s pencil marks in Humboldt’s books to notes on Humboldt’s work in Darwin’s notebooks such as ‘In Humboldt great work’ or ‘Humboldt has written on the geography of plants’.

7 Humboldt wrote in Personal Narrative: ‘The beasts of the forest retire to the thickets; the birds hide themselves beneath the foliage of the trees, or in the crevices of the rocks. Yet, amid this apparent silence, when we lend an attentive ear to the most feeble sounds transmitted by the air, we hear a dull vibration, a continual murmur, a hum of insects, that fill, if we may use the expression, all the lower strata of the air. Nothing is better fitted to make man feel the extent and power of organic life. Myriads of insects creep upon the soil, and flutter round the plants parched by the ardour of the Sun. A confused noise issues from every bush, from the decayed trunks of trees, from the clefts of the rock, and from the ground undermined by the lizards, millepedes, and cecilias. There are so many voices proclaiming to us, that all nature breathes; and that, under a thousand different forms, life is diffused throughout the cracked and dusty soil, as well as in the bosom of the waters, and in the air that circulates around us.’

18

Humboldt’s Cosmos

‘THE MAD FRENZY has seized me of representing in a single work the whole material world,’ Humboldt declared in October 1834. He wanted to write a book that would bring together everything in the heavens and on earth, ranging from distant nebulae to the geography of mosses, and from landscape painting to the migration of the human races and poetry. Such a ‘book on Nature’, he wrote, ‘ought to produce an impression like Nature herself’.

At the age of sixty-five, Humboldt began what would become his most influential book: Cosmos. A Sketch of the Physical Description of the Universe. It was loosely based on his Berlin lecture series, but the expedition to Russia had given him the final comparative data he had needed. A colossal endeavour, Cosmos was like a ‘sword in the breast that now has to be drawn’, he said, and the ‘opus of my life’. The title, Humboldt explained, came from the Greek word κόσμος – Kosmos – which meant ‘beauty’ and ‘order’, and which had also been applied to the universe as an ordered system. Humboldt now used it, as he said, as a catchphrase to express and encapsulate ‘both heaven and earth’.

And so, in 1834, the very year that the term ‘scientist’1 was first coined, heralding the beginning of the professionalization of the sciences and the hardening lines between different scientific disciplines, Humboldt began a book that did exactly the opposite. As science moved away from nature into laboratories and universities, separating itself off into distinct disciplines, Humboldt created a work that brought together all that professional science was trying to keep apart.

Because Cosmos covered a vast range of subjects, Humboldt’s research rippled into all conceivable areas. Aware that he didn’t and couldn’t know everything, Humboldt recruited an army of helpers – scientists, classicists and historians – who were all experts in their fields. Well-travelled British botanists happily sent him long lists of plants from the countries they had visited. Astronomers handed over their data, geologists provided maps and classicists consulted ancient texts for Humboldt. His old contacts in France proved useful too. A French explorer obliged by sending Humboldt a long manuscript about Polynesian plants, for example, while close friends from Paris such as François Arago were at Humboldt’s regular disposal. At times Humboldt asked specific questions or enquired which pages he should consult in which book, and at others he sent out long questionnaires. When chapters were completed, he would distribute proof pages with gaps that he requested his correspondents to fill in with the relevant numbers and facts, or he would ask them to correct his drafts.