The Seeds of Life Page 13

  In truth, this was a theory to set nearly anyone’s head spinning. In Adam’s body were testicles; in those testicles were sperm cells; in those sperm cells were miniature proto-humans; in their testicles were micro-miniature proto-humans, who had testicles of their own, within which… and so on, forever. (If one of those infinitesimally small proto-humans happened to be female, she might grow up to have children with some man; his sperm cells would contain miniature proto-humans whose sperm cells contained even tinier proto-humans, and the whole process would continue along that new branch of the family tree.)

  To modern minds, the theory seems impossibly far-fetched, and biology textbooks for a century have delighted in mocking it. But the mockery is misguided. This silly-sounding theory was espoused by men who were not in the least bit silly. Many of them were brilliant, and all of them were serious. (It is worth noting, too, that nearly everyone in the 1600s believed that the Earth was a mere six thousand years old. That meant that Adam and Eve lived only a few hundred generations ago, which made the sequence of Russian dolls a bit less daunting to contemplate.)*

  What would strike a later age as impossibly far-fetched impressed the seventeenth century as grand and inspiring. In a sense, the doctrine was a counterpart to today’s string theory, the “theory of everything” that many of the most esteemed figures in physics have been laboring on for decades. Both theories purported to explain nothing less than the nature of reality; both gleamed with intellectual rigor; both took abstraction so far that theorists swooned and experimentalists shuddered.

  When physicists today discuss their work, they take for granted that their theories are impossibly arcane. That is not a sign of trouble, as they see it, but merely a fact about the world. Edward Witten is sometimes hailed as the greatest living physicist. In a recent interview, he waved aside objections that string theory is so far from what humans can picture or experiments can test—it bristles with such mysteries as extra dimensions that hide, curled up, so that we cannot see them—that it is more poetry than science. Those complaints were beside the point. “The majesty of string theory” was the point. “The universe wasn’t made for our convenience,” Witten snapped. In the 1600s, thinkers might have grown dizzy at the notion of an infinite succession of ever-tinier living beings, one within the other, and of those lives unreeling across endless centuries. What of it? Who said that finite man can grasp the ways of his all-wise, all-seeing Creator? The proper response to the theory, one early scientist observed, was “holy awe.”

  Nor did it count as a mark against the theory of preformation that, even armed with their newfangled microscopes, scientists could not see these infinitesimally small dolls. They carried on unfazed, like Einstein and his fellow scientists in the twentieth century who deduced the existence of atoms they could not see. Preformation’s great virtue was intellectual, not visual. It did not reveal the world, but it made sense of it. As one naturalist proclaimed, in rhyme:

  We must believe

  What Reason tells: for Reason’s piercing Eye

  Discerns those Truths our Senses can’t descry.

  You cannot explore what you cannot imagine. In the 1600s and 1700s, scientists could not imagine a world without God. Tied to a particular notion of the divine plan, they fashioned an argument whose every link they deemed indisputable. They ran into trouble not because they indulged in wild flights of imagination but because they had such faith in logic that they followed their argument no matter where it led them. Mesmerized by the power of reason, earnest scientists ran alongside Alice and through the looking glass.

  IT WAS FAITH IN A PERFECT, ALL-POWERFUL GOD THAT PROVIDED the sturdiest pillar for this new doctrine. But other strong arguments bolstered the same case. Look at a tulip bulb, observed the French philosopher and priest Nicolas Malebranche, in 1672, and you can see the tulip’s structures already present in miniature. This is still a classroom exercise today.

  A renowned Italian biologist named Marcello Malpighi reported an analogous finding, in 1674, this time in chickens. Like Aristotle and Harvey before him, Malpighi had examined chicken eggs as they developed, day by day. Unlike his predecessors, he had used a microscope rather than his naked eye. Within a new-laid egg, Malpighi informed the Royal Society, he could already discern the embryo’s structure. This was exactly in keeping with the doctrine of preformation. Malpighi was one of the great authorities on the microscope, and his judgment carried weight. (He was mistaken, though, because he did not realize that the embryo starts growing before the egg is laid. What he took to be the embryo’s earliest moment was actually a scene from later on in the tale.)

  These reports of tulips and chickens were scattered examples, but scientists’ hope and expectation was that they foretold the general story. Like the first crocuses of spring, they carried a message not of flukiness but of bounty soon to come. As microscopes improved, countless new organisms would no doubt unveil their own preformed, tidily bundled structures.

  But in the meantime, even before microscopes had gained the power to show those preformed structures, they had revealed sights that made that outcome seem inevitable. Every facet of every creature ever examined, no matter how tiny and elusive, turned out to be exquisitely made. That didn’t prove that every blurry, out-of-focus image concealed a sharp image within, but it certainly implied such a conclusion. Jonathan Swift, who was fascinated with both telescopes and microscopes, wrote his famous lines on the flea in 1733:

  So, Nat’ralists observe, a Flea

  Hath smaller Fleas that on him prey,

  And these have smaller Fleas to bite ’em;

  And so proceed ad infinitum.

  The words “ad infinitum” were more than a clever rhyme. Swift and his contemporaries took literally the notion that living creatures could grow smaller forever. A century later, with the advent of cell theory, biologists would learn that nature comes with size limits. Living organisms are made of cells, it would turn out, and anything alive must be at least one cell big. (We can imagine an infinitely tiny cell, but in practice there can be no such thing because even one-celled organisms must contain certain fixed-size parts, like water molecules.) But in the 1700s, microscopists’ astonishing reports seemed to tell a different story.

  So did the brilliant success of the newest and most powerful weapon in the physicists’ armory. This was calculus, a kind of conceptual microscope that Isaac Newton and his followers used to dissect the workings of the heavenly clockwork. Newton’s invention (to his fury, his rival Gottfried Leibniz had made the same breakthrough) was built explicitly on the idea of “infinitesimals,” which were infinitely short distances and infinitely brief stretches of time.

  Since the days of Zeno and his infuriating paradoxes, about four hundred years BCE, mathematicians and philosophers had been terrified by the notion of infinity. To contemplate infinity was to flirt with madness. The great intellectual breakthrough that Newton and Leibniz achieved late in the 1600s—the breakthrough that had eluded Archimedes and all his successors for nearly two millennia—was finding a way to freeze-frame the moving, changing world by slicing it up into infinitely many still images. Then, with reality pinned down like a slide under a microscope, they could zoom in and examine each scene in close-up.*

  Archimedes and any of the others might have done it. Mathematics requires no equipment beyond pen and paper, and the Greeks had mastered all the necessary intellectual tools. What they lacked was nerve. Newton and Leibniz had nerve in superabundance. They harnessed infinity and revolutionized the world. For scientists in the 1600s and 1700s, the moral seemed plain: If the key to understanding the physical world was to look in ever greater close-up, why wouldn’t exactly the same key unlock the secrets of the living world?

  ANTONY VAN LEEUWENHOEK, FAR TOO IMPATIENT A CHARACTER to wander for long in the thickets of philosophy, rarely spoke out on the Russian doll theory. He preferred to focus on making the case for the sperm, and not the egg, as the key factor in conception. Occasionally, though
, in brief passages in his letters to the Royal Society, he ventured into the open. In a letter in August 1688, he boiled his argument down to a single axiom, like a line in Euclid: “God, Lord and Omniscient Maker of the Universe, makes no new creatures.” That single premise contained implicit within it the whole theory, much as Adam’s loins contained the whole history of humankind.

  Leeuwenhoek took pains to head off likely criticisms of his spermist views. He warned his fellow scientists that they might find it almost unimaginable that “in an Animalcule from the Male sperm, which is so incredibly small, so great a mystery as a Human body can be enveloped.” But there were no limits to the miniature marvels the microscope had revealed. Why shouldn’t the animalcule theory be true, when Leeuwenhoek had seen millions upon millions of tiny, complicated creatures occupying a space no bigger than a grain of sand?

  Yes, it was astonishing, he scolded. Of course it was! But what was the point in wailing, “I can’t believe it!” Like it or not, it seemed likely that “an animalcule from the male seed of whatever members of the animal kingdom, contains within itself all the limbs and organs which an animal has when it is born.” (He never explained just how those embryos would grow, but the idea seems to have been that they would unfold along built-in lines, a bit like those toys for toddlers where a tiny, nondescript bit of sponge dropped into water opens up into a duck or a dinosaur.)

  Leeuwenhoek went out of his way to emphasize that he did not believe that the proto-human within the sperm cell was a minuscule but perfectly proportioned human being. His claim was only that the proto-human contained all the parts that would one day grow to make a proper human. During the course of development those proportions might change drastically; nearly any sort of stretching and shifting was possible. The point was merely that no new parts could appear out of the blue.

  In the meantime, new evidence had come along to bolster Leeuwenhoek’s case. Just as he had proclaimed, living creatures had been preformed all along.

  The evidence came from a most unlikely direction.

  THIRTEEN

  THE MESSAGE IN GOD’S FINE PRINT

  SINCE EARLIEST TIMES, HUMANS HAD DONE THEIR BEST TO IGNORE the whole buzzing, biting, teeming insect world. Butterflies and bees were fine, but who didn’t despise flies and fleas? And then, for scientists at least, the world shifted. Starting late in the 1600s, they focused intently on insects, with fascination and deep respect. These tiny, intricate creatures were important in their own right, scientists explained, but that was the least of it. More important, insects pointed to truths that applied across the living world, all the way to humans.

  One reason for the focus on insects was practical: they were easy to find, easy to study, and short-lived. Like fruit flies in modern-day genetics labs, insects made ideal research tools for scientists eager to probe the secrets of sex and growth. But, as so often was the case in the 1600s and 1700s, the deeper reason had to do with religion.

  The more that scientists scrutinized insects, the more they found to marvel at, from the brilliant sheen of a beetle’s shell to the intricate structure of a fly’s compound eyes. They drew what they took to be the inescapable conclusion: here was new insight into God’s cosmic design. By the time they were done, they felt confident that they had seen to the heart of the mystery. They knew not just how insects develop and grow, but how all life grows. This was the fruit of attending God’s message even when he chose to express himself through the least likely of messengers.

  Think of how people furnish a home, the argument went. Anyone might make a fuss over the chairs and rugs in the living room, where visitors were sure to congregate. But if a seldom-visited back bedroom was impeccable, too, that spoke of genuine care and diligence. So it was, scientists reckoned, with insects—even a slapdash creator might do his best on a handful of showy creations, comets and chestnut trees and human beings. But only an infinitely patient, infinitely skilled artist would employ his full powers on the tiniest, most hidden facets of the natural world. “The Deity is as conspicuous in the structure of a Fly’s paw,” one French naturalist declared, “as He is in the bright Globe of the Sun itself.”

  Book after book set out the message. The title of one—The Theology of Insects, or Demonstration of the Perfection of God in All That Concerns Insects—spoke for all the others. The lowliest creature inspired hymns to Divine Wisdom. “What has been said of the lilies of the field may be justly ascribed to the Ichneumon fly…,” one writer exclaimed. “Solomon in all his glory was not arrayed like one of these.”*

  God’s delicate craftsmanship demonstrated a virtuoso’s talent, just as a spinning wheel in a doll house would be more impressive than one built to an ordinary scale. But the breadth of God’s handiwork—the sheer number and variety of insects, each one perfectly constructed—made the story yet more impressive. One early scientist expressed his awe in rhyme:

  FIGURE 13.1. Artists as well as scientists marveled at the intricacies of insect design. This meticulously observed watercolor, from around 1575, is by the Flemish artist Joris Hoefnagel.

  God is greatest in ye Least of things

  And in the smallest print we gather hence

  The world may Best read his omnipotence.

  Jan Swammerdam, the pious Dutch anatomist who flourished in the 1660s and ’70s, was among the greatest of the scientists who took insects to be coded messages from God. “And God created great whales,” the Bible tells us. Swammerdam preferred to point to the other end of the spectrum. “I offer you the Omnipotent Finger of God in the anatomy of a louse,” he exclaimed, for in that tiny body “you will find miracle heaped on miracle.”

  In the strange process of insect development, Swammerdam saw the key to human development, too, as we shall see. In particular, he saw irrefutable proof of the Russian doll theory, which he was one of the first to describe. His discoveries would win him acclaim but never contentment. Unhappy, ambitious, guilt-racked, brilliant, Swammerdam reproached himself for his base motives. “I have striven night and day to surpass others and to raise myself above them with ingenious inventions and subtle techniques,” he confessed. How could his research truly honor God when his heart was so impure?

  But he worked incessantly. Hour upon hour, for days on end, he stared through his microscope at the intestines of the butterfly or the sex organs of the bee. (It was Swammerdam who found, in 1668, that the “king” bee was actually a queen. The scientific world reeled in astonishment.)*

  In his quest to sort out the riddles of sex and conception, Swammerdam roamed throughout the animal kingdom. “All God’s works are governed by the same rules,” he declared, and therefore insight might come from any direction. Swammerdam had done pioneering work on the human ovaries and uterus, as we have seen, and later he moved far beyond humans and far beyond dissections.

  Taking up a single, newly fertilized frog egg, he tried to dissect it in the hope of unveiling the secret mechanism within. Swammerdam was a talented artist and a brilliant anatomist, adept at the most demanding microsurgery, but he had taken on an impossible task. In short order, he noted forlornly, he had reduced an intricate arrangement of tissue to nothing but a broken mess, “crushed, and otherwise disturbed by my handling it.” To probe the egg with razor and tweezers was akin to plucking apart a spider web while wearing mittens.

  Such blundering was rare. The mark of Swammerdam’s style was a delicate hand and a reverential eye. Often he contented himself with painstaking observation. He studied the mating behavior of frogs with attentiveness and a kind of fondness. “The male Frog leaps upon the female and when seated on her back… he most beautifully joins his toes between one another, in the same manner as people do their fingers at prayer.” The image presumably came immediately to the mind of the devout Swammerdam.

  FIGURE 13.2. Mating snails as depicted by Swammerdam. The spiraling shapes at the center are the animals’ penises.

  Snails, too, drew Swammerdam’s sympathetic gaze. He described their curious mod
e of sex in a chapter of his masterpiece, The Book of Nature, and he decorated the title page of another book with a pair of snails in flagrante. Snail sex proceeds, appropriately, at a snail’s pace, perhaps because there is a great deal to negotiate. Snails are hermaphrodites, and over the course of slow-motion sexual bouts lasting two or three hours, each partner tries to impregnate the other.

  In Swammerdam’s account of these slow and slimy hijinks, the fs in the place of ss rendered the text almost quaint. The snails go about their bufinefs, he explained, and then, “After all is finished, the little creature, having wantonly consumed the strength of life, becomes dull and heavy; and thence calmly retiring into its shell, rests quietly without much creeping, until the furious lust of generation gathers new strength.” Omne snail post coitum triste est.

  MANY ANIMALS INTRIGUED SWAMMERDAM, BUT INSECTS OBSESSED him. Since childhood, he had collected them with fanatic energy, trapping and netting and trading and buying thousands upon thousands of prizes. His father maintained a famous cabinet of curiosities, a mini-museum in his Amsterdam home that featured such miscellaneous wonders as Roman coins and colossal snakeskins. Young Swammerdam had amassed his own cabinet, but he stuck almost entirely to insects.

  This fascination—“an almost uncontrollable passion,” in the words of one early biographer—persisted to the end of Swammerdam’s life. The study of insects proved the ideal way for him to combine his anatomical skills with his mission of honoring God. By 1669, he had been out of medical school for two years. To his father’s dismay, he devoted his time almost exclusively to collecting insects rather than patients. The old man cut his son off. Who would throw away a lucrative career so that he could study vermin?

  Swammerdam waved aside such worldly questions. When others read of his discoveries, they would worship God with newfound fervor. He would slay his enemies not with the jawbone of an ass, like Samson, but with the genitals of a cheese mite or a stag beetle. “What atheist who considered the inexhaustible artistry of the internal organs of [these] animals would not be ashamed and dumbfounded, my Lord?” he cried.