SEVENTEEN
THE CATHEDRAL THAT BUILT ITSELF
FRUSTRATED BY THE QUESTION OF HEREDITY, SCIENTISTS IN THE mid-1700s turned to a related mystery. This challenge was so basic that it had been overlooked, as we overlook many things we take for granted. Forget about black hair and blue eyes and other details for a minute, scientists now asked. What about this? How does a baby know how to grow at all? How does a helpless infant “know” to become a toddler and then a teen?
The question was both unavoidable and unapproachable. If preformation was not the answer, where did you begin? Perhaps there was some vital force within the body that directed its growth, as had sometimes been suggested. That had a certain ring to it, but it was too vague to help much. But consider for a minute what a proper explanation would require. One of the leading thinkers of the age, the Swiss anatomist Albrecht von Haller, wrote in 1752 that he could not imagine a “force that would be sufficiently wise to join together… millions and millions of vessels, nerves, fibers, and bones.”
A novelist and a poet as well as a scientist, Haller had talent and ambition to spare. Still, he acknowledged that when it came to the mystery of how life organizes itself, he could do little more than confess his bewilderment. Without a “building master” to supervise the assembly of the microscopic bits and pieces of the developing embryo, Haller wrote, gruesome accidents would be universal. “An eye might stick to a knee, or an ear to a forehead.”
Preformation’s great appeal had always been that it offered a way to deal with these objections, or at least to dodge them. How an embryo transformed into a baby was not a mystery because there was no transformation; there was only growth and unfolding. Just as important, preformation was a mechanistic theory, one that depicted the world as a place of pushes and pulls rather than of forces, auras, and emanations. In the early 1700s, to think in this cogs-and-wheels way marked a scientist as a sensible problem-solver and not a wooly-minded dreamer. But as preformation came under attack in the middle decades of the 1700s, the clockwork picture came to seem narrow and misguided, at least when it came to the living world.
And especially when it came to sex. Some scientists, even a few who had been the most enthusiastic about mechanistic theories of the cosmos, had been sounding the alarm for decades. Bernard de Fontenelle was a French writer famous in the 1600s and 1700s for his popular accounts of science. In his best-known book he had proclaimed flat out that “the universe is but a watch on a larger scale.” Fontenelle was a worldly, sociable man who lived to within a month of his one hundredth birthday and remained a fixture at every literary salon and elegant dance until the end (“Ah madame,” he sighed, on meeting one famous beauty, “if only I were eighty again!”). But despite his devotion to clockworks and to romance both, Fontenelle made a point of emphasizing that the two did not belong together.
As early as 1683, at the height of the Scientific Revolution, Fontenelle had mocked his fellow mechanists for overreaching. They had tried to import their clockwork explanations from physics into biology. Fontenelle would have none of it. “You say that Beasts are Machines, just like Watches?” he challenged. But everyone knew what happened when you put a “Male Dog Machine next to a Female Dog Machine.” Soon you had little Puppy Machines. “Whereas two Watches”—the machines that represented human engineering at its most sophisticated—“might be together all their Life-time, without ever producing a third Watch.”
Such objections had not risen to the status of deal breakers early on, because clockwork explanations had been so much in vogue. That faith stemmed from physicists’ success in explaining the solar system. Then Robert Hooke and Antony van Leeuwenhoek had come along and inspired hope that the microscope would do for biology what the telescope had for astronomy. That was especially easy to believe since the two inventions were so closely related. (Galileo made his observations of the microworld essentially by looking through the wrong end of his telescope.)
The pioneering generation of anatomists had shown that life’s secrets were written in minute script. The microscope seemed like the perfect tool for deciphering what one scientist called the “mystical letters” in those God-dictated texts. And anatomy was only part of the story. All the tiny building blocks that formed the world could now be studied facet by facet. One early scientist thought that in time microscopes might reveal “the Solar Atoms of light” and “the springy particles of air.”
But one of the major scientific trends of the age was the collapse of these high hopes. No matter how diligently they worked, biologists in the 1700s found that life did not come into sharper and sharper focus but grew ever dimmer and stranger and more baffling.
This was deeply disillusioning. The microscope’s all-seeing eye, Hooke had forecast in Micrographia, would confirm the mechanistic picture of the world. In the past, he noted with disdain, thinkers had indulged themselves in idle guesswork and dreamy speculation. No more. With science’s new tools, empty chatter would “give place to solid Histories, Experiments, and Works.”
Hooke had a firm idea of what those experiments would show. We might “discern all the secret workings of Nature,” he wrote eagerly in 1665, and we would see that the whole intricate system was “managed by Wheels, and Engines, and Springs [akin to those] devised by human Wit.” Even memories might have an actual, physical shape. Hooke suggested they might look something like curled-up snakes sleeping in a cave, a “continued Chain of Ideas coiled in the Repository of the Brain.”
Those hopes were soon dashed. First, technical problems proved maddeningly obstinate. You could not simply put your eye to a microscope and look around at the micro-landscape, like a sailor scanning the sea through a spyglass. Under the microscope’s lens, colors faded, and opaque objects grew transparent. “It is exceedingly difficult in some Objects, to distinguish between a prominency and a depression,” Hooke lamented, or between a reflection and a surface or a shadow and a stain.
The telescope had been easier to understand and easier to trust. You could look at a church steeple half a mile off through a telescope. Then you could walk closer and confirm that what you had seen matched reality. And when you turned that telescope to the heavens, the picture continued to make sense. The most exotic objects looked reassuringly like those we knew already—the moon had mountains, like the Earth; Jupiter had moons, like our moon; and Venus had phases, like the moon. But look through a microscope, and what you saw was baffling and unexpected.
Or hideous. We have already met scientists who cringed at the sight of wormlike sperm cells. Many other observers were just as squeamish.* Jonathan Swift, who was fascinated and repelled by science in equal measure, devoted long passages of Gulliver’s Travels to the creepiness of a world looked at too closely. At one point in the novel, which appeared in 1726, Gulliver lifted a tiny man to his cheek for a look around. From ground level, Gulliver’s skin had appeared “fair and smooth.” But now the Lilliputian recoiled in horror. “He said he could discover great holes in my skin; that the stumps of my beard were ten times stronger than the bristles of a boar, and my complexion made up of several colors altogether disagreeable.”
Swift’s judgment was mild in comparison with many of his peers. “If our eyesight were enlarged,” one horrified writer declared in 1727, a year after Gulliver’s Travels, “we should appear to be the most amazing Spectacle in the whole World: there should we see an infinite Number of Worms swimming in the Blood, and sallying from the Heart through the Arteries, and returning back by the Veins.” Everywhere you looked, whether in eyes or nose or ears, you would find countless living, burrowing animals. “We should see not only the Brain full of them, but the Flesh abounding with them, and the very Bones perforated by them; and Thousands every Moment crawling through the Pores of the skin.”
The telescope enthralled; the microscope appalled. That had not always been so. From the telescope’s earliest days, the prospect of stars stretching to infinity, stars beyond counting, had inspired awed thoughts of a might
y Creator. So had the micro-wonders seen through the microscope, at least for pioneering investigators like Swammerdam.
But even Swammerdam, perhaps the most pious of all the great microscopists, found himself aghast nearly as often as he was entranced. The natural world revealed through the microscope was not only shimmering butterfly wings but swooping death and cruel, devouring jaws. “How then can we avoid crying out, ‘O God of miracles! How wonderful are all thy works!’” Swammerdam exclaimed, only to lament, a few words later, “All nature is over-run, and covered with a kind of leprosy [that] weighs down our senses and disturbs our reason.”
Such qualms were far from universal. But as time passed, more scientists lost faith. They continued to find new microstructures, many of them dazzlingly complex, but they could not fathom why God had indulged himself in such showmanship. Once those flourishes and curlicues had inspired hymns of praise. Now the notion of endless intricate details in a mite’s intestines stirred dismay and puzzlement. God seemed less a hurler of lightning bolts than the sort of mad eccentric who devoted his energies to inscribing verses on a grain of rice.
In physics the guiding principle, at least since Newton, had been that the simplest and most elegant solution to a problem was almost certainly the correct one. This doctrine was enshrined with a name, Ockham’s razor, as a reminder of the virtue of cutting theories down to their sparest form. The telescope had only strengthened that belief. Nature was mathematical, precise, and austere. But then came the microscope, and nature seemed messy, exuberant, and overflowing.
To this day, biologists new to the subject find themselves taken aback by nature’s tolerance for make-do solutions. (The eye is wired backward, for instance, so that we have a blind spot in our vision. Similarly, we’re at risk of choking with every bite we eat because only a flap separates the passageways for food and air.) Nature’s designs represent a tinkerer’s improvisations, not an engineer’s perfectionism. Simple designs, it turns out, may not be nature’s choice. That is a hard truth to face, as Francis Crick, perhaps the greatest biologist of the twentieth century, liked to point out. (Crick had begun his scientific career as a physicist.) “Many a young biologist,” Crick observed, “has slit his own throat with Ockham’s razor.”*
That was a modern insight. Isaac Newton had proclaimed that “it is ye perfection of God’s works that they are all done with ye greatest simplicity,” and in the 1700s, Newton reigned as almost a scientific god.† It counted as a black mark against the microscope that it besmirched the view of science linked with his name. In time, the microscope would once again take on crucial importance. But that moment was far in the future.
ALONG WITH THESE PRACTICAL AND PSYCHOLOGICAL OBJECTIONS to the microscope came yet another. This time the problem was philosophical. Distressingly, staring through the microscope presented you with discovery upon discovery without ever seeming to bring you nearer to the truth. The hope had been that the microscope would let you see beneath the surface, as if you could see past a clock’s face to the cogs and gears behind it.
To everyone’s frustration, it turned out not to work that way. You could see the cogs and gears, it was true, but you could not see what role they played. To do that, it seemed plain, you had to look closer. Which, with great effort, scientists managed to do. But beneath each level of complexity they found another level just as complex. And each time they managed to bring the new image into focus, the old one slipped from sight, like a suspect disappearing into the fog.
The fear arose that perhaps the entire strategy of looking in ever more detail was misguided. If the questions you were really after were, What is life? Where does new life come from? Where do babies come from? then you might map anatomical structures more and more obsessively without drawing any closer to your goal. For modern-day scientists, the analogy might be trying to tell time by looking at the atoms of a clock, or studying the brain ever more minutely in order to learn, Where does hope come from? Where do ideas come from?
The brilliant French scientist Blaise Pascal had raised this objection early on. To look through a microscope was to dive into nothingness, he had argued, to plunge through endless layers and never touch bottom. Even inside the body of a mere flea, Pascal wrote, were “legs with joints, veins in its legs, blood in its veins, humors in the blood, corpuscles in the humors, vapors in the corpuscles,” and so on, forever. Dive as deep as you like, and would you eventually find treasure? No, replied Pascal, but only “a new abyss.”
In the beginning Pascal’s pessimism had been a minority view. Then, after days and years spent staring at drops of water and flecks of blood, other scientists began to sound the same dismaying notes. Next John Locke and other philosophers joined in. If God had meant us to see the hidden world, he would have given us eyes suitable to the task. Alexander Pope, who had a gift for putting the reigning doctrines of the day into bite-sized form, reproached scientists for not knowing their place. “Why has not Man a microscopic eye? / For this plain reason, Man is not a Fly.” The path of wisdom was to recognize that some of God’s secrets lay beyond humankind’s investigative powers.
THE END CAME QUICKLY. AS EARLY AS 1692, ONLY A FEW DECADES after he had first stared through the microscope, Hooke declared that the game was over. The “subjects to be enquired into are exhausted,” he wrote, “and no more is to be done.” The microscope, which had been greeted with such high hopes, was fit for nothing but “Diversion and Pastime.”
That had left Leeuwenhoek almost alone, except for a handful of amateur naturalists happily examining flower petals and butterfly wings. Leeuwenhoek never wavered in his devotion to the microscope, but after a decade or two of work he conceded that he would not solve the riddle of sex and development. It was not that the riddle had no answer, in his judgment, but that the answer was written in a script so tiny that it would remain forever beyond the range of even the best microscopes. What Leeuwenhoek called the “great secret” would remain a secret. He carried on undaunted, working away even knowing that he would never grasp victory.
Leeuwenhoek’s accomplished and melancholy predecessor Swammerdam had reached the same conclusion via a different path. Nature would always hold secrets in reserve because finite humans could not unravel all the mysteries spun by an infinite God. That was disheartening, even though it did testify to God’s grandeur. Leeuwenhoek, a more practical and less pious man than Swammerdam, framed things in a cheerier way. He focused his gaze on his rivals around him, not on the heavens above him. He may not have reached his goal, but he had outdistanced all his peers, and that was satisfaction enough.
By the time the grand old man closed his weary eyes for the last time, in 1723, nearly every scientist had set his microscope aside. Confused and adrift, biologists pondered their predicament. The microscope was out, which deprived them of what had seemed their most promising tool. Preformation was out, which deprived them of their guiding theory. Most important, the mechanistic approach was out, which deprived them of a framework with which to make sense of the world.
Where do babies come from? Two thousand years after Aristotle, almost a century after William Harvey, the answer seemed further off than ever.
WITH THE INTELLECTUAL STRUCTURES THEY HAD TRUSTED NOW collapsed on the ground, even geniuses wandered bewildered through the rubble. The breakdown of the mechanistic view, it soon emerged, was the most disorienting loss. Living creatures are born, and then they grow, and eventually they die. The machine view seemed to throw light only on the last of those phases. Perhaps humans and animals wore out and died much as machines rusted and broke down.
But death and decay were the easy half of the equation; what about life and growth? These were the truly enticing challenges, and the most elusive. “The history of a man for the nine months preceding his birth,” the poet Samuel Taylor Coleridge remarked, “would probably be far more interesting than all the three-score-and-ten years that follow it.” Even the most familiar examples of life and change presented dark mysteries. Whe
n trees grew taller, where did the new wood come from?* What about animals, which not only grew larger but also grew and regrew hair and antlers and other odds and ends? No machines did anything like that. And those questions arose when you pondered a single, isolated organism. Where were the machines that could make a new machine?
Scientists looked more closely at Fontenelle’s mocking comparison of dogs and clocks, from decades before. It was even worse than Fontenelle had said. If animals really were cog-and-gear contrivances like clocks, think how strange those clocks would have to be in order to reproduce. Imagine two parent clocks. To replicate themselves in the way that living creatures do, each parent clock would somehow have to spit out a mini-machine made of scavenged gears and wheels (while continuing to tell the time itself).
Those two whirring, clicking gizmos would join together, every cog and wheel fitting just so, to form a new mini-clock, which would then grow ever larger. (The new clock would grow in two senses: individual gears and wheels would grow larger, and whole new sets of perfectly spinning, turning, meshing gears would somehow come into being.) And, through this entire astonishing process, the new-made clock would have to tick along in perfect order.
No one in the 1700s had ever seen such a machine. Nor has anyone today.
WE HAVE THE GREAT ADVANTAGE OVER OUR INTELLECTUAL forebears, as discussed in the previous chapter, of knowing all about computers and other programmable machines. Without those examples to draw on, growth and development were nigh-to-impenetrable mysteries. But it is worth noting that even from today’s vantage point and with the wonders of modern technology firmly in mind, the tricks that the body pulls off still retain the power to amaze.
In modern accounts of science, the sections on how organisms grow constantly invoke “recipes” and “blueprints” and “instructions.” They should—those analogies are essential. But the familiar words may fool us into forgetting just how bizarre the process of human development (or animal development) truly is. The problem is that we hear the word “recipe” and automatically picture someone in the kitchen measuring and stirring.
The Seeds of Life Page 18
