The Seeds of Life

ONE

ONWARD TO GLORY

BY THE LATE 1600S, THE ERA WHEN THE SCIENTIFIC WORLD began to take on its modern shape, explorers had circled the globe and mapped the heavens. They had calculated the weight of the Earth, traced the paths of comets that cut the sky only once in a lifetime, and divined the secret of the Milky Way. They had uncovered the mathematics at the heart of music and discovered the laws of perspective, so that an artist armed only with a paintbrush could pin reality to his canvas. But for thousands of years, long after Columbus and Magellan and Galileo, the deepest scientific riddle of all lay unsolved.

Where do babies come from? Such geniuses and creators of the modern era as Leonardo da Vinci and Isaac Newton did not know. They knew, that is, that men and women have sex and as a result, sometimes, babies, but they did not know how those babies are created. They did not know that women produce eggs, and when they finally discovered sperm cells, they did not know that those wriggly tadpoles had anything to do with babies and pregnancy. (The leading theory was that they were parasites, perhaps related to the newly discovered mini-creatures that swam in drops of pond water. This was Newton's view.)

Not until astonishingly recent times—in 1875, in a seaside laboratory in Naples, Italy—was the mystery of where babies come from finally solved.

Until then everything to do with conception and development was wrapped in darkness. For centuries, scientists struggled to find out if the woman merely provides a fertile field for the man's seed, or if she produces some kind of seed of her own. They did not know how twins come to be. (Too much semen? Two bouts of sex in quick succession? Sex with two different men?) They did not know if conception is more likely on the night of a full moon or a new moon or if timing makes any difference at all. They did not know, though they assumed, that a baby has only one father, as it has only one mother. They did not know why babies resemble their parents, and sometimes one parent more than the other.

Where do we come from? How does life begin? These were the most urgent of all scientific questions. The world is festooned with mystery and miracle. But not everyone has wondered why the stars shine or why the Earth spins. Every person who has ever lived has asked where babies come from. For millennia, the deepest of thinkers (and every ordinary person) had pondered this cosmic riddle.

No one had a clue.

PART OF THE REASON FOR THE PERPLEXITY WAS STRAIGHTFORWARD. We tend to forget how astonishing the story of life truly is. We've heard the explanation so often that we take it to be common sense. Every fourth grader knows where babies come from. Both parents contribute equally, we learn early on, the mother providing an egg and the father sperm. Each month one of a woman's ovaries releases an egg, which travels through a Fallopian tube toward her uterus. If a couple has sex at the right time, some of the millions of sperm cells in a man's semen make their way from her vagina and cervix toward that egg. One of those sperm cells may fuse with the egg. In time that newly merged cell divides into two joined cells, and then into four and eight and so on. After nine months, a new human being bursts, howling, into the world.

The truth is so far-fetched that it is a wonder that anyone believes it.

In textbook accounts of science, far-seeing researchers systematically gather facts and pile them in sturdy and imposing towers. The story of sex and babies was nothing like that steady advance toward a goal. The scientists who finally solved the case ventured off course for decades at a time. They raced at top speed down long, dark alleys chasing suspects who turned out to have airtight alibis. They concocted elaborate scenarios that collapsed in fantasy. They wandered in a daze, stymied by observations they could not fit into any pattern. They found some clues by deep and careful investigation and others by tripping over them as they raced in the wrong direction in the dark.

Progress came in fits and lurches, but that is the way with all true mysteries. Only in old-school television does insight arrive on cue, just in time for the closing credits. The problem was not that the scientists were incompetent—they were human and fallible, but many were dazzlingly intelligent, and nearly all were diligent—but that the truth was so well concealed.

To crack the case, scientists would need new tools, notably the microscope, and new ideas, notably the insight that the body is made of cells, trillions upon trillions of them, which all arise from a single progenitor. More than tools and ideas, they would need whole new ways of thinking. Suppose, for a moment, that some early savant had somehow leapt to the true conclusion that a living organism begins as a single cell. What then? Immediately scientists would have found their path blocked by a Sphinx posing a bewildering follow-up riddle—how does that single tiny cell "know" how to transform itself into a gurgling, six-pound baby?

Tackling that question would have required these early scientists to understand that a living organism could assemble itself! Through most of the history of the world, this was unthinkable, as outlandish as the idea that a cathedral could build itself. Today it is a concept hammered into every student who takes high school biology.

The path to that insight was tangled and difficult. It required, among other things, drawing analogies from machines like player pianos and, later, computers, that carried out complicated actions by following instructions written in code. In the twentieth century, such mechanical devices would lead to the discovery that life itself followed instructions written in a genetic code. But in the 1600s and 1700s no such machines existed; no one could look at the ghostly motions of a player piano's keys, governed by a musical roll, and shout, "Eureka!"

Instead, scientists looked around them in every direction for clues to the riddles of conception and development. How could it possibly work? Baffled but determined, they ventured down the most unlikely paths. They studied insects with obsessive care, for example, in the hope that those startling transformations—a wriggling caterpillar inside its cocoon emerges as a butterfly with gossamer wings!—would throw light on the changes in infants and babies. They studied fish and frogs and dogs and deer to see what they shared in the way of anatomy and mating behavior. They tackled the narrowest of questions—How do snails, which have both male and female genitals, sort out who will do what to whom?—and the grandest of themes—Do living organisms possess a "vital force" that sparks them to life?

Often a quest that started in one direction ended far afield, in a landing spot no one had anticipated. The search for the vital force, for instance, led to strange and dangerous experiments with electricity and lightning, and even an encounter with Dr. Frankenstein and his monster.

In hindsight, that zigzag progress seems inevitable, for two seemingly different questions were deeply entangled. The question, Where do babies come from? proved impossible to separate from What is life? Thus, straightforward inquiries about sperm and eggs and anatomy opened up into profound riddles about the nature of living organisms. Scientists who merely wanted to know about the body's nooks and crannies found themselves wondering what the world was made of. How could it be that the same, ordinary stuff that forms lumps of mud and murky puddles, when rearranged in the right way, can burst into crying, crawling life?

This was, moreover, an era when science and religion wrapped around one another, so that every statement about life implied a judgment about God the Creator. With one peek through a microscope, a scientific observation could provoke a religious battle.

The search for the solution to the sex and conception mystery would consume careers and span centuries. My focus is on the heart of the tale, from about 1650 to nearly 1900. During that time, scientists in half a dozen countries—in Holland, France, England, Germany, Italy, even the newborn United States—would pass the torch, or burn their hands and drop it. It is surprising, in hindsight, that it did not take them longer.

THEY SET OUT, NOT WITH HESITANCY OR TREPIDATION, BUT WITH eagerness and swagger, for their peers had just won a colossal victory. In a torrent of discoveries all through the 1600s, physicists and astronomers had demonstrated that the universe was a clockwork, the stars and planets its cogs and wheels. Spirits and demons had been banished. Nature obeyed laws and equations, not caprice. Comets were not heavenly messengers. God was a mathematician.

The seventeenth century was a tumultuous age, bubbling over with intellectual ambition. The roll call of genius went on and on. Shakespeare, Galileo, Rembrandt, Descartes, Newton were not busts on a library shelf but flesh-and-blood titans who wielded almost unfathomable powers. The secrets of the human heart and the natural world seemed destined to give way before them.

The scientists in that starry roster shared not merely an ambition but a way of thought. From Galileo and Newton on, they believed with an unshakable faith that their mission was to study God's creation and proclaim the glory of his craftsmanship. This they had begun to do, and when they rattled off the list of their triumphs they were making a twofold claim. First, they had done great things. They had unraveled the rainbow and harnessed the tides. Second, and just as important, they had cracked a cosmic code. They had found out how to think of the world: it was an encrypted message written by God.

The world was not just beautiful, like a painting that moved onlookers to delight; it was a beautifully constructed riddle that contained secrets within secrets. Humankind's highest task, these early scientists fervently believed, was to solve that riddle, the better to honor the Creator. (And why had God made matters so difficult? If he wanted trembling homage, why not arrange the stars to spell out BEHOLD in letters of fire? For the devout scientists of the 1600s, the answer was plain. God had given humankind its defining gift, a far-ranging intellect, and he meant for us to use it.)

The book of nature was written in the language of mathematics, Newton and his contemporaries insisted, and only the mathematically literate could read it. This was an austere view. Romantic poets would later howl that the scientists' "cold philosophy” had drained the world of its sap and energy, as if a lush Gauguin landscape had been set aside in favor of a diagram in a geometry textbook.^* But despite their somber mathematical talk, the scientists of the seventeenth century tackled the world with gusto and high hopes.

They talked of God the mathematician, but they seemed to picture him in less imposing terms. Francis Bacon, one of the pioneers of the Scientific Revolution, took this to an extreme. His God seemed less the Almighty on a celestial throne than an indulgent parent who had devised an Easter egg hunt for a pack of toddlers. God "took delight to hide his works," wrote Bacon, "to the end to have them found out."

Bolstered by their successes in understanding the physical world, scientists made bold plans to continue their advance, this time moving to living creatures. If the proud heart could be understood as a pump, the rest of the body seemed sure to follow. Muscles and bones and arteries would play the roles of levers, pulleys, and pipes; food would serve for fuel; filters and springs, plumbs and bellows, would all have their natural counterparts.

In time, the body would yield its secrets like a watch opened up on a craftsman's bench. Humans and animals would show themselves as more wondrous versions of the ingenious mechanical figures that adorned the clock towers of Europe's cathedrals and emerged, on the hour, to march a few proud steps and raise trumpets to their metal lips.

The inner workings of life, the deepest mysteries of how animals move and breathe and reproduce, would be unveiled. God, who had placed the stars in the sky and carved towering mountains, had surely lavished even greater care on the details of a bird's wing and a whale's fin and, especially, on the human beings he had fashioned in his own image.

Scientists pictured the living world as a straightforward target. The inanimate world, with its hurtling planets and remote, untouchable stars, seemed more forbidding, and, indeed, Newton and his peers had needed to invent a mathematical language to describe it. Even today, we think of physics, with its black holes and hidden dimensions and parallel universes, as the realm of the incomprehensible. Biology, in contrast, deals with everyday, literally down-to-earth objects like dogs and plants and snails. Scientists had conquered physics even so. Biology would fall, too. They would make quick work of it.

They didn't. The bold men of science raced off to take on the mystery of life and promptly face-planted. Life was messy, it turned out almost at once, fragile and unpredictable and maddeningly coy about its secrets. A cannonball in flight plainly has no desire to go this way rather than that. Why shouldn't a few simple laws suffice to describe its motion? But consider the gulf between a chunk of metal and a sunflower craning toward the light, or a dog tugging on its leash, or a human being. On the one side, mere matter. On the other, breathing, pulsing life. How could the same sort of laws account for both?

Planets were easy; plants were hard. And sex and reproduction proved hardest of all. For nearly three hundred years, from about 1600 until nearly 1900, the question of where babies came from defeated one thinker after another. The vanquished lay in heaps, like soldiers on a battlefield. Late in the 1700s one scientist took the trouble to compile a list of failed theories. Scanning the centuries, he tallied "262 groundless hypotheses." ("And nothing is more certain," one eminent biologist remarked at once, "than that his own system is the 263rd.")