Shadows of Forgotten Ancestors

by Carl Sagan

  Darwin was criticized by some for being a teleologist—for believing that Nature was working with some long-term end in view—and, conversely, by others for constructing a Nature in which random, purposeless variation is key. (“The law of higgledy-piggledy,” the astronomer John Herschel dismissively called it.) People had real difficulty grasping the concept of natural selection. His motives, sincerity, honesty, and ability were all questioned. Many who criticized him did not understand his argument or the cumulative power of the data he invoked in its support. Many—including some of the most distinguished scientists of the day, among them, painfully, Adam Sedgwick, his old geology professor—rejected Darwin’s insight, not because the evidence was against it, but because of where it led: seemingly, to a world in which humans were degraded, souls denied, God and morality scorned, and monkeys, worms, and primeval ooze elevated; “a system uncaring of man.” Thomas Carlyle called it “a Gospel of dirt.”

  None of these moral and theological criticisms is compelling, Darwin, Huxley, and others labored to show: In astronomy, we no longer believe that an angel pushes each planet around the Sun; the inverse square law of gravitation and Newton’s laws of motion suffice. But no one considers this a demonstration of the nonexistence of God, and Newton himself—except for a private reservation about the notion of the Trinity—was close to the conventional Christianity of his day. We are free to posit, if we wish, that God is responsible for the laws of Nature, and that the divine will is worked through secondary causes. In biology those causes would have to include mutation and natural selection. (Many people would find it unsatisfying, though, to worship the law of gravity.)

  As the debate proceeded over the years, natural selection seemed less strange and less threatening. Increasing numbers of scientists, literary figures, and even clergymen were won over. But by no means all. In July 1871, The London Quarterly Review—which eleven years earlier had published Bishop Wilberforce’s anonymous diatribe—remained unreconstructed, wholly missing Darwin’s point. “Why should natural selection favor the preservation of useful varieties only? Such action cannot be referred to blind force; it can belong to mind alone.” Not only are evolution and natural selection rejected, but so is the newly discovered law of the conservation of energy,12 one of the foundations of modern physics.

  Some of the underlying emotional reasons for rejecting natural selection were later vividly expressed by the playwright George Bernard Shaw:

  [T]he Darwinian process may be described as a chapter of accidents. As such, it seems simple, because you do not at first realize all that it involves. But when its whole significance dawns on you, your heart sinks into a heap of sand within you. There is a hideous fatalism about it, a ghastly and damnable reduction of beauty and intelligence, of strength and purpose, of honor and aspiration, to such casually picturesque changes as an avalanche may make in landscape, or a railway accident in a human figure. To call this Natural Selection is a blasphemy, possible to many for whom Nature is nothing but a casual aggregation of inert and dead matter, but eternally impossible to the spirits and souls of the righteous … If this sort of selection could turn an antelope into a giraffe, it could conceivably turn a pond full of amoebas into the French Academy.13

  Fine words. But what if undreamed-of powers lie hidden in “inert and dead matter,” given 4 billion years of preserving what works? Such objections address (and far from compellingly) only the philosophical and social implications of natural selection, and not the evidence for it.

  Naive Darwinists, including many capitalists, have self-servingly argued that oppression of the weak and the poor is a justified application of natural selection to human affairs. Naive biblical literalists, including some high officials charged with safeguarding the environment, have self-servingly argued that the destruction of non-human life is justified because the world will shortly end anyway, or because of the injunction in Genesis that we have “dominion … over every living thing.”14 But neither evolution nor the sacred books of various religions are invalidated because dangerous conclusions have been mistakenly drawn from them.

  By the 1870s and 1880s, the evidence amassed by Darwin was changing many minds. Reviews were acknowledging “the certainty of the action of natural selection,” and even the possibility that humans evolved from some lower animal.15 However, some of the conclusions of Darwin’s 1871 book, The Descent of Man, stuck in the craws of even the most sympathetic reviewers. The debate, we find, had moved into a new arena:

  We deny [animals] … the power of reflecting of their own existences, or of inquiring into the nature of objects and their causes. We deny that they know that they know, or know themselves in knowing In other words, we deny them reason.

  We return to this new level of debate later, and here note only how quickly many of the theological reservations about evolution had dissipated as Darwin’s argument became better understood. “Nothing is more remarkable,” he wrote in his Autobiography, “than the spread of scepticism or rationalism during the latter half of my life.”16

  ——

  Of innumerable modern examples of natural selection in the real world, we select one—of interest because it involves humans and because it is the outcome of an experiment, although one performed inadvertently and under tragic circumstances. Malaria is endemic among nearly half the people of the world (just before World War II, the number was two thirds of all humans). It is a serious illness associated, in the absence of appropriate medicine or natural immunity, with high mortality. Even today several million people die from it each year. When the Plasmodium parasite causing malaria is injected (usually by mosquito bite) into the bloodstream, it eventually invades the red blood cells that carry oxygen from the lungs to every cell of the body. The red blood cells are rendered sticky, adhere to the walls of very small blood vessels, and are prevented from being circulated to the spleen—which destroys Plasmodium parasites. This is good for the parasites and bad for the humans.

  People in malarial zones of tropical Africa, as elsewhere, have an adaptation to malaria, the sickle-cell trait. Under the microscope some of the red blood cells do look a little bit like sickles or croissants. But in someone with the sickle-cell trait, the altered red blood cells are surrounded by needle-like microscopic filaments that work, it is suggested, a little like a porcupine’s quills. The parasites are impaled or otherwise damaged, and the red blood cells—protected from the parasites’ sticky proteins—are then carried to the “untender mercies” of the spleen. With the parasites dead, many of the red blood cells return to their normal state, “unruffled” by the experience.17 However, when the genes for this trait are inherited from both parents, serious anemia, obstruction of the small blood vessels, and other infirmities often result. The trade-off, it is natural to think, is that it’s better for a part of the population to be seriously anemic than for most of the population to be dead of malaria.

  In the seventeenth century slave traders from Holland arrived in the Gold Coast of West Africa (present-day Ghana). They bought or captured slaves in large numbers and transported them to two Dutch colonies—Curaçao in the Caribbean and Surinam in South America. There is no malaria in Curaçao, so the sickle-cell trait conferred anemia but no compensating advantage to the slaves brought there. But malaria is endemic in Surinam, and the sickle-cell trait was often the difference between life and death.

  If now, some three centuries later, we examine the descendants of these slaves, we find that those in Curaçao show hardly any incidence of the trait, while it remains prevalent in Surinam. In Curaçao the sickle-cell trait was “selected against”; in Surinam, as in West Africa, it was “selected for.” We see natural selection operating on very short time scales, even for such slowly reproducing beings as humans,18 As always, there is a range of hereditary predispositions in a given population; the environment elicits some but not others. Evolution is the product of a hand-in-hand interplay between heredity and environment.

  ——

  At
the end of his life, Darwin called himself a theist, a believer in a First Cause. He had doubts, though:

  [C]an the mind of man, which has, as I fully believe, been developed from a mind as low as that possessed by the lowest animal, be trusted when it draws such grand conclusions?19

  Evolution in no way implies atheism, although it is consistent with atheism. But evolution is clearly inconsistent with the literal truth of certain revered books. If we believe the Bible was written by people, and not dictated word-for-word to a flawless stenographer by the Creator of the Universe, or if we believe God might on occasion resort to metaphor for clarity, then evolution should pose no theological problem. But whether it poses a problem or not, the evidence for evolution—that it has happened, apart from the debate on whether uniformitarian natural selection fully explains how it happened—is overwhelming.

  The Darwinian perspective is central to all of modern biology, from investigations of the molecular structure of DNA to studies of the behavior of apes and men.20 It connects us with our long-forgotten ancestors and our swarm of relatives, the millions of other species with whom we share the Earth. But the price exacted has been high, and there are still—especially in the United States—those who refuse to pay, and for very human and fathomable reasons. Evolution suggests that if God exists, God is fond of secondary causes and factotum processes: getting the Universe going, establishing the laws of Nature, and then retiring from the scene. A hands-on Executive seems to be absent; power has been delegated. Evolution suggests that God will not intervene, whether beseeched or not, to save us from ourselves. Evolution suggests we’re on our own—that if there is a God, that God must be very far away. This is enough to explain much of the emotional anguish and alienation that evolution has worked. We long to believe that there’s someone at the helm.

  ——

  Darwin’s transcendantly democratic insight that all humans are descended from the same non-human ancestors, that we are all members of one family, is inevitably distorted when viewed with the impaired vision of a civilization permeated by racism. White supremacists seized on the notion that people with high abundances of melanin in their skin must be closer to our primate relatives than bleached people. Opponents of bigotry, perhaps fearing that there might be a grain of truth in this nonsense, were just as happy not to dwell on our relatedness to the apes. But both points of view are located on the same continuum: the selective application of the primate connection to the veldt and the ghetto, but never, ever, perish the thought, to the boardroom or the military academy or, God forbid, to the Senate chamber or the House of Lords, to Buckingham Palace or Pennsylvania Avenue. This is where the racism comes in, not in the inescapable recognition that, for better or worse, we humans are just a small twig on the vast and many-branched tree of life.

  Natural selection has been misused by capitalists and communists, whites and blacks, Nazis and many others to grind this or that self-serving ideological axe. It’s not surprising that feminists feared that a Darwinian perspective would provide yet another cudgel for male seientists to hit women over the head with—about alleged inferiorities in mathematics or statecraft. But for all we know, such a perspective might reveal, that the raging hormonal imbalances that propel men to violence make them less than optimal for leadership of a modern state. If we believe sexism to be a prejudicial error, that fact will emerge from scientific examination, and we should favor its rigorous scrutiny by the methods of science.

  Much of the recent controversy over the application of Darwinian ideas to human behavior has been motivated by the fear of such misuse by racists, sexists, and other bigots—as indeed happened with ghoulish and tragic consequences in World War II. However, the cure for a misuse of science is not censorship, but clearer explanation, more vigorous debate, and making science accessible to everyone. If some of our proclivities are inborn, as surely must be the case, it hardly follows that we cannot learn to modify, mitigate, enhance, or redirect the resulting behavior.

  ——

  Vice-Admiral FitzRoy had been the British Board of Trade’s weatherman for more than a decade when his 1865 long-range forecast proved to be wildly, calamitously wrong. The proud, choleric FitzRoy took a terrible beating in the newspapers. When he could no longer bear the ridicule, he slit his throat, an early martyr to the predictive failures of meteorology. Although FitzRoy had spoken publicly against Darwin in the “creationism” controversy and despite the fact that the two men had not been face-to-face in eight years, Darwin took the news of FitzRoy’s suicide badly. What images from the youthful adventure they shared must have come to Darwin’s mind? “What a melancholy career he has run,” he observed to Hooker, “with all his splendid qualities.”21

  On melancholia, too, Darwin was something of an expert. These years he was depressed, exhausted, and sick most of the time. Throughout this miserable period he was consistently productive and his relationships with Emma, the survivors among their ten children, and a great number of friends seemed none the worse for it. If anything, the letters they exchanged and their written recollections testify to an openness, an emphasis on the importance of feelings, a respect for children, a harmonious family life. His daughter remembered him saying that he hoped none of his children would ever believe something just because it was he who told it to them. “He kept up his delightful, affectionate manner towards us all his life,” his son Francis wrote. “I sometimes wonder that he could, with such an undemonstrative race as we are; but I hope he knew how much we delighted in his loving words and manner … He allowed his grown-up children to laugh with and at him, and was generally speaking on terms of perfect equality with us.”22

  There were many who comforted themselves with the thought that in his last moments Darwin would renounce his evolutionary heresies and repent. There are still people today who piously believe that’s just what happened. Instead, Darwin faced death calmly and apparently without regret, saying on his deathbed “I am not the least afraid to die.”23

  The family wished to bury him on their estate at Down, but twenty Members of Parliament, with the support of the Anglican Church, appealed to them to allow him to be interred at Westminster Abbey, a few feet away from Isaac Newton. You’ve got to hand it to the Church of England. It was an act of consummate grace. For you, they seemed to be saying, who have done the most to raise doubts about the truth of what we say, we reserve the highest honor—a respect for the correction of error that is, incidentally, characteristic of science when it is faithful to its ideals.

  HUXLEY AND THE GREAT DEBATE

  Thomas Henry Huxley was born to a large, struggling, dysfunctional family in the England of 1825, where class was destiny for almost everyone. His formal education consisted of two years of elementary school. But he had an insatiable hunger for knowledge and legendary self-discipline. At age seventeen, on an impulse, Huxley entered an open competition given by a local college, and was awarded the Silver Medal of the Pharmaceutical Society and a scholarship to study medicine at Charing Cross Hospital. Forty years later he was President of the Royal Society, then the foremost scientific organization in the world. He made fundamental contributions to comparative anatomy and many other fields, and was, along the way, inventor of the words “protoplasm” and “agnostic.” Through his whole life he was committed to teaching science to the public. (More than one member of the upper classes was known to don shabby clothes in order to gain admittance to his lectures for working people.) He taught that a fair scientific examination of the facts demolished European claims of racial superiority.24 At the end of the American Civil War, he wrote that while the slaves might now be free, half of the human species—women—had yet to be emancipated.*

  One of Huxley’s interests had been the idea that all animals, including us, were “automata,” carbon-based robots, whose “states of consciousness … are immediately caused by molecular changes of the brain-substance.”25 Darwin closed his last letter to him with these words: “Once again, accept my cordial thanks,
my dear old friend. I wish to God there were more automata in the world like you.”26

  “If I am to be remembered at all,” Huxley confided late in life, “I would rather it should be as ‘a man who did his best to help the people’ than by any other title.”27 What he is actually best remembered for is delivering the punch line in the decisive debate that gained acceptance for Darwin’s ideas.

  ——

  The Huxley/Wilberforce debate is the grand climactic scene in the 1930s Hollywood movie version that might be imagined of Darwin’s life:

  A small item on the front page of The Daily Oxonian: “Annual Meeting of British Association for the Advancement of Science to Be Held Tomorrow.” The dateline reads June 29, 1860. Front page begins to spin like a roulette wheel.

  Dissolve to reveal that we are following the highly imaginative, although slightly shady Robert Chambers (played by Joseph Cotten) as he makes his way down an Oxford street. He is jostled by another man and just as he turns in annoyance, he realizes that it is none other than the pugnacious Thomas Henry Huxley (Spencer Tracy), whose conviction with regard to the truth of his friend Darwin’s controversial theory is so fierce it will one day earn him the nickname “Darwin’s Bulldog.”

  Rascal that he is, Chambers can’t resist asking Huxley if he’ll he attending Drapers reading at the British Association meeting. The title is to be “The Intellectual Development of Europe with Reference to the Views of Mr. Darwin.” Huxley claims he’s too busy.

  Knowingly, Chambers allows that “ ‘Soapy Sam’ Wilberforce is sure to be there.”

  Huxley, growing more defensive, insists that it would be a waste of time.

  Chambers says slyly, “Deserting the cause, Huxley?”