Authors: Carl Sagan,Ann Druyan
The scientific revelations of the European Enlightenment had posed disturbing challenges to the biblical account of the Earth’s origin and history. There were those who tried to reconcile the new data and new insights with their faith. They held that Noah’s flood was the primary agent responsible for the present configuration of the Earth’s crust. A big enough flood, they thought, could transform the Earth’s geology in just forty days and forty nights, consistent with an Earth only a few thousand years old. With a little spin control on a literal reading of the Book of Genesis, they felt they had managed to pull it off.
Lyell had been a lawyer for as long as he could stand it. When he was thirty years old, he abandoned the law for geology, his true passion. He wrote
Principles of Geology
to advance the “Uniformitarian” view that the Earth has been shaped by the same gradual processes that we observe today, but operating not merely over a few weeks, or a few thousand years, but ages. There were distinguished geologists who held that floods and other catastrophes might explain the Earth’s landforms, but that the Noachic flood wasn’t enough. It would take
catastrophes. These scientific Catastrophists were
comfortable with Lyell’s long time scales But for the biblical literalists Lyell posed an awkward problem. If Lyell was right, the rocks were saying that the Bible’s six days of Creation, and the age of the Earth deduced by adding up the “begats,” were somehow in error It was through this apparent hole in
would sail into history.
Hired mainly as FitzRoy’s companion and sounding board, Darwin was obliged to bear with equanimity the Captain’s politically conservative, racist, and fundamentalist harangues. For most of the voyage, the two men managed to maintain a truce with regard to their philosophical and political differences. However, Darwin was simply unable to let FitzRoy’s opinion on one particular issue go unchallenged:
[A]t Bahia, in Brazil, he defended and praised slavery, which I abominated, and told me that he had just visited a great slave-owner, who had called up many of his slaves and asked them whether they wished to be free, and all answered “No.” I then asked him, perhaps with a sneer, whether he thought that the answers of slaves in the presence of their master was worth anything? This made him excessively angry, and he said that as I doubted his word we could not live any longer together.
Darwin fully expected to be kicked off the ship. But when the gunroom officers heard of the row, they vied with each other for the privilege of sharing their quarters with him. FitzRoy calmed down and actually apologized to Darwin, rescinding the eviction. Possibly, Darwin’s evolutionary views emerged, in part, out of his exasperation with FitzRoy’s inflexible conventionalism, and the necessity of the young man to suppress for five years the counterarguments that were welling up inside him
Perhaps it was the legacy of his grandfathers that enabled Darwin to detect the inconsistencies and injustices that other members of his social class would not see. At the very beginning of his book,
The Voyage of the Beagle
, he tells of a place not far from Rio de Janeiro:
This spot is notorious from having been, for a long time, the residence of some runaway slaves, who, by cultivating a little ground near the top, contrived to eke out a subsistence. At length they were discovered, and a party of soldiers being sent, the whole were seized
with the exception of one old woman, who, sooner than again be led into slavery, dashed herself to pieces from the summit of the mountain. In a Roman matron this would have been called the noble love of freedom: in a poor negress it is mere brutal obstinacy.
Darwin had been lured to South America by the prospect of discovering new birds and new beetles, but he couldn’t help noticing the carnage the Europeans were inflicting. Colonial arrogance, the institution of slavery, the extirpation of countless species for the enrichment and entertainment of the invaders, the first depredations of the tropical rain forest—in short, many of the crimes and stupidities that haunt us today—troubled Darwin at a time when Europe was confident that colonialism was an unalloyed benefit for the uncivilized, that the forests were inexhaustible, and that there would always be enough egret feathers for every millinery shop until the Day of Judgment. In part because of these sensitivities, in part because Darwin always wrote as clearly and directly as he could—striving to communicate to the greatest number of people—
The Voyage of the Beagle
is still a stirring and accessible adventure story.
However, this book has watershed status because it was during the course of the expedition it recounts that Darwin began to amass the great body of evidence—not intuition, but data—that makes the case for evolution by natural selection. “At last gleams of light have come,” he was later to write, “and I am almost convinced that species are not (it is like confessing a murder) immutable.”
The Galapagos is an archipelago of thirteen good-sized islands and many smaller ones lying off the coast of Ecuador. If all the species on Earth were immutable, then why did the beaks of the otherwise very similar finches on islands separated by no more than fifty or sixty miles of ocean vary so dramatically? Why narrow, tiny, pointy beaks on the finches of one island and larger, parrot-like curved beaks on the finches of the next? “Seeing this gradation and diversity of structure in one, small intimately related group of birds,” he later wrote in
, “one might really fancy that, from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.” (These volcanic islands, we now know, are less than 5 million years old.) And it wasn’t just the finches that raised such problems, but the giant tortoises and the mockingbirds, too.
Back in England, Henslow and Sedgwick had been reading Darwin’s
letters aloud at meetings of scientific societies. When Darwin returned home in October 1836, he found he had acquired something of a reputation as an explorer and naturalist. His father was now well pleased with him, and all talk of a parsonage ceased. The same month he met the geologist, Lyell, for the first time. Though not without its rough spots, it was to be a lifelong friendship.
Darwin made important contributions to geology. His interpretation of coral reefs—that they mark the locations of slowly subsiding sea-mounts that had once been islands—was substantiated on the
and corresponds to the modern understanding. In 1838 he published a paper arguing that earthquakes, volcanoes, and the thrusting up of islands are all caused by slow, intermittent, but irresistible global motions in the semi-liquid interior of the Earth. This “almost prophetic”
thesis, as far as it goes, is part and parcel of modern geophysics. In his 1838 Presidential Address to the Geological Society, William Whewell mentioned Darwin’s name (in the context of this work) more than twice as often as any other geologist, living or dead. In geology, following Lyell, as in biology, Darwin championed the idea that profound changes are worked little by little over vast intervals of time.
In 1839, he married his cousin, Emma Wedgwood. Through ten children and more than four decades they shared a deep, loving, and almost entirely harmonious relationship. During their early married life he was writing down, but certainly not for publication, his first tentative sketch for a theory of evolution. Their rare differences were over religion. “Before I was engaged to be married,” he wrote in his autobiography, “my father advised me to conceal carefully my doubts, for he said that he had known extreme misery thus caused with married persons.”
A few weeks after their wedding, she wrote to him:
May not the habit in scientific pursuits of believing nothing till it is proved influence your mind too much in other things which cannot be proved in the same way, and which if true are likely to be above our comprehension?
Years later, Darwin wrote at the bottom of Emma’s letter,
When I am dead, know that many times,
I have kissed and cried over this.
He tried his best to avoid the public version of this domestic tension. Our past was then a dark and shameful secret. To expose it would have been perceived by many as an affront to the prevailing religious norms and as an assault against human dignity. But to suppress it would have been to reject the data because the implications were disturbing. Darwin recognized that if he was to convince anyone he would have to support his argument with a compelling body of evidence.
In 1844, a sensational book, fundamentally pseudoscience, called
Vestiges of the Natural History of Creation
was published. Robert Chambers, the encyclopedist and amateur geologist who was its anonymous author, claimed that he had traced human ancestry all the way back to … frogs. Chambers’ reasoning was half-baked (although no more so than Erasmus Darwin’s) but its audacity attracted a great deal of attention. Nagging doubts about Creation were beginning to bubble to the surface, and Darwin felt that he should write down his own theory in as irrefutable a form as possible. He expanded a short essay, begun two years before, into a two-part work entitled “On the Variation of Organic Beings under Domestication and in the Natural State” and “On the Evidence Favourable and Opposed to the View That Species Are Naturally Formed Races Descended from Common Stock.” However, he was not ready to publish. He wrote a letter to Emma that he asked be considered as a codicil to his will. In the event of his death, he wanted her to
devote £400 to its publication and further will yourself … take trouble in promoting it—I wish that my sketch be given to some competent person, with this sum to induce him to take trouble in its improvement and enlargement.
He felt he was on to something important, but feared—perhaps especially in view of his frequent bouts of illness—that he would not live to complete the work.
In what superficially seems an odd next move, he now put his evolutionary studies aside and for the next eight years devoted his life almost exclusively to barnacles. His great friend, the botanist Joseph Hooker, would later observe to Darwin’s son, Francis, “Your father had Barnacles on the brain from Chili [Chile] onwards!”
It was this
exhaustive project that really earned him his credentials as a naturalist. Another close friend, the anatomist and brilliant polemicist Thomas Henry Huxley, observed that Darwin
never did a wiser thing … Like the rest of us, he had no proper training in biological science, and it has always struck me as a remarkable instance of his scientific insight, that he saw the necessity of giving himself such training, and of his courage, that he did not shirk the labour of obtaining it … It was a piece of critical self-discipline, the effect of which manifested itself in everything [he] wrote afterwards, and saved him from endless errors of detail.
Darwin had not been the only scientist to get a jolt from Chambers’
. Alfred Russel Wallace, a surveyor who had become a naturalist, was also unimpressed with Chambers’ arguments, but also intrigued by the notion that there was a knowable process at work in the evolution of life. In 1847, he traveled to the Amazon in search of factual support for this idea. A fire on the ship taking him back to England consumed every one of his specimens. Wallace persevered, setting off to the Malay Peninsula to gather a new collection. In the September 1855 issue of
Annals and Magazine of Natural History
, his paper “On the Law Which Has Regulated the Introduction of New Species” appeared.
By this time, Darwin had been wrestling with such problems for two decades. Now, it was entirely possible that his claims of priority to the solution of life’s greatest mystery would be snatched away. If science were in the business of conferring sainthood, the conduct of Darwin and Wallace towards one another would have earned it for them both. Darwin wrote a letter of hearty congratulation to Wallace in which he mentioned how long he’d been working on the same problem.
Darwin’s friends Huxley and Hooker prodded him to quit stalling and write the paper that would make an ironclad case for evolution. He complied and was nearing its completion in 1858, while Wallace, now in Indonesia and sick with malaria, tossed and turned, grappling with the question “Why do some die and some live?”
Emerging from his stupor, he understood natural selection. He wrote “On the Tendency of Varieties to Depart Indefinitely from the Original Type” and promptly mailed it to Darwin, asking him to use his judgment about
what should be done with it. Darwin was distressed to see how very close Wallace’s work was to his own writings of 1839 and 1842. In 1844 he had combined them into an essay, but it remained unpublished. Darwin turned to his friends for guidance on how to deal ethically with this dilemma. Hooker and Lyell came up with a wise solution: Present both the Wallace paper and a version of Darwin’s unpublished 1844 essay at the next meeting of the Linnaean Society and publish them together in the Society’s
Thereafter, Wallace always spoke of evolution as being Darwin’s theory and Darwin always credited Wallace with its independent discovery. Darwin now applied himself to the task of writing the book that would cause so much trouble.
On November 24, 1859,
The Origin of Species
was published. The first edition of 1,250 copies was snapped up by the booksellers. Darwin had been careful to make only one reference to humans in the whole book: “Light will be thrown on the origin of man and his history.”
Anything more from his pen on this delicate matter would have to wait another twelve years, for the publication of
The Descent of Man
. His restraint fooled no one. Given its formidable armamentarium of data, there could be no reconciling
with a literal rendition of Genesis.