CHAPTER ONE
SEASHELLS

Word of the marvel reached the Medici palace in Florence. The Grand Duke Ferdinand II, an aficionado of natural history, ordered that the shark be brought at once so that his court scientists could examine it. But it was too huge, and its flesh had already begun to putrefy. The fishermen hacked off the head and threw the rest of the corpse into the sea. The head was loaded onto a cart to be sent up the valley of the Arno to Florence.

The year was 1666. Florence, indeed all of Europe, was in a state of transition. The Renaissance had pretty much run its course. The Protestant Reformation was a done deal. The Age of Enlightenment, on the other hand, was barely on the horizon. It was an awkward, in-between age – reborn, reformed, but not yet enlightened.

A generation earlier, the Pope had forced Galileo Galilei to renounce his belief in the Copernican theory of the solar system. Galileo had based his opinions on his own observations of the sky, rather than on the Church-approved texts: Aristotle and the Bible. And though he accepted his punishment, he held firm to his convictions about science. True scientific knowledge came from experiments and direct observation of nature, he believed, not from books, even sacred ones. He lived out his final years in Florence, protected by the Grand Duke. Now Ferdinand’s court was home to a scientific academy founded by several of Galileo’s former pupils determined to keep his spirit alive.

Newest to the group was a diminutive, soft-spoken anatomist from Denmark named Nicolaus Steno. Only 28 years old, he was already famous for his acute powers of observation and his preternatural skill with a scalpel. His discoveries had created sensations in Amsterdam and in Paris, the twin intellectual capitals of Europe. His bold challenges to conventional theories about the heart and the brain had inevitably made him enemies, but also won him many admirers. The Florentine scientists welcomed him as one of their own. When the monstrous shark head arrived in Florence and was brought into the anatomical theater to be dissected, it naturally fell upon Steno to do the honors.

The chance capture of a shark and its dissection by a young scientist eager to prove himself before a prestigious Italian court marked the unlikely beginning to an intellectual revolution that, in its way, was as profound as that of Galileo and Copernicus. Their revolution had shifted the human position in space: It dislodged us as the fixed center of the cosmos and set our world in motion. Steno’s changed our place in time. It removed us from the center of the standard Biblical narrative and gave our world a new history. The time encompassed by this new history expanded from a mere six thousand years to nearly five billion. Vastly older than the human species, the world could no longer be claimed as our exclusive domain.

Steno discovered that the crust of the earth contained an archive of its most ancient history. Up until that time, scholars had relied only on the written word – the Bible and the texts of the Ancients – to delve into the past. To the new philosophers of the burgeoning Scientific Revolution, the past had been irrelevant: They were interested in nature’s timeless laws, not its historical development. Because no one had ever tried to read the chronicle recorded in the Earth’s geologic strata, no one grasped the stupendous changes the world had undergone over its staggeringly long past. But without this perspective, nothing about the forces that shape our physical world – earthquakes, volcanoes, erosion, climate – could ever make scientific sense. The static, mechanical concept of the world had to be replaced by a dynamic, evolutionary one.

This revolution in our understanding of the Earth, triggered by Steno, gathered momentum slowly. Not until the end of the eighteenth century was it in full swing; not until the middle of the twentieth century was it complete. It was resisted as bitterly by scientists as by theologians. It was embraced more readily by Romantic poets than by Enlightenment philosophers. Ironically, the man who launched it never publicly challenged the six-thousand-year Biblical timescale that his science eventually overturned. Yet even in his final years, which he devoted entirely to religion, he never renounced his science either.

The story of Steno is full of such ironies–and of pathos, as well. The genius of his ideas was never fully appreciated during his lifetime. He died young, at 48. At one time a scientist and darling of one of Europe’s most lavish courts, he became at the end of his life an ascetic priest. His poverty and fasting, said one friend, had reduced him to "a living corpse."

But that day in Florence he was still at the height of his scientific powers. He had a medical education that, typically for the times, had covered everything from anatomy to astrology. He had the support of a wealthy sovereign. And, most important, he had a mind given to taking unexpected leaps. From the shark, it leaped to a seemingly unrelated question, one that, old as it was, could still generate heated debate. It was not only his answer to this question, but the way he sought to prove it, that triggered the scientific exploration of the world’s distant past.

The question was this: Why are seashells often found far from the sea, sometimes embedded in solid rock at the tops of mountains? The ancient Greeks had known and written about these seashells. Medieval theologians had noticed them in the building stones of their cathedrals. Miners and quarrymen found them, as did farmers, shepherds, and travelers. Even the Pope in Rome must have noticed them and wondered, because they littered the slopes of Vatican Hill.

Today we think it natural to say that the seashells were left by a sea that once covered the land. This, in fact, was the explanation offered by the ancient Greeks. The very earliest of the Greek philosophers, the so-called Pre-Socratics, made it the keystone of their various theories of the world, six centuries before Christ. Aristotle continued the tradition, writing that the waxing and waning of the seas were part of the world’s "vital process." The land naturally experienced many inundations over the course of time.

Yet most educated people of Steno’s time rejected this idea. They thought instead that the shells grew within the Earth. Despite all appearances, the seashells were not actually seashells at all. No clams had ever lived inside the fossil clam shells; no seas had ever covered the mountains.

Bizarre as it may seem today, this idea made perfect sense to the seventeenth-century mind. Some of the more mystical currents of Renaissance thought were still popular, even among those who prided themselves for their rationality. Neo-Platonists and Hermetic philosophers had taught that all things on and within the Earth were shaped by "plastic forces" and invisible emanations from the stars. No one knew how these mysterious forces and emanations actually produced stones in the shapes of seashells, but the world was a mysterious place: No one knew how a magnet’s force caused it to attract an iron bar or orient itself toward the north. No one knew how the sun’s "emanations" made flowers grow. These things happened in front of the eyes, yet they were still mysterious. Who could say what was or was not possible in the depths of the Earth?

The theory that fossil seashells grew right there in the rocks also had the advantage of sidestepping some thorny problems faced by other explanations. There was, for example, a long tradition among Christian writers that fossil seashells were relics of Noah’s flood. The shells were tangible proof of scripture and a visible reminder of God’s power and human sinfulness. Missionaries found them useful for demonstrating to the local pagans that the flood described in the Bible had been universal, not something inflicted on the Hebrews alone.

But a closer look at both scripture and fossil seashells led to disconcerting questions. There were contradictions, some easier to reconcile than others. The shells resembled species that lived in salt water, but forty days and nights of rain would have made a freshwater flood. And how could so many shellfish become spread so widely in a flood that, according to the Bible, lasted no more than a year? Medieval monks had felt free to fudge a little in their reading of the text. Maybe it was the overflowing sea that caused the flood, not rain, as was written. Maybe it had lasted somewhat longer than the text said. It was a respectable practice. Saint Augustine and the other early church fathers had not hesitated to interpret scripture metaphorically when necessary.

There was another, stickier, problem, though, one that metaphors couldn’t easily solve. The Bible said God created the solid Earth and gave it its form in the very first week. Noah’s flood happened much later. How, then, how did seashells get inside rocks, which had supposedly already been created when the flood took place? The flood might have left shells on mountains, but not in them.

Of course, it was possible to call them a miracle, and leave it at that, but the budding scientific minds of the seventeenth century were reluctant to do this. They wanted to explain the world by natural law whenever possible. And since the Reformation, metaphorical interpretations of Scripture had become increasingly frowned upon, too. Luther and Calvin had put the Bible at the center of their faith; the plain meaning of its words were not to be trifled with.

Even the "vital processes" suggested by Aristotle offered no way out of the dilemma. It may have been a perfectly acceptable explanation for low-lying shell deposits near the coasts, but for the shells in the mountains, it could lead to dangerous ideas. Aristotle had emphasized the slowness of geographical changes. In the time it would take for an ocean to dry up, or a mountain to sink beneath the waves, whole nations might arise and perish. He imagined an eternal world–as many pagans of his time did–which put no limits at all on time, and he claimed that these natural inundations occurred again and again over the ages. For the modern seventeenth-century man, this simply could not be true. There was not enough time. Nothing of the sort had ever been seen in all the centuries of recorded history. Mount Sinai still stood as high as it had when Moses brought down the Ten Commandments. The Mediterranean Sea had not dried up appreciably, either. How, then, could geography have been overhauled many times when the world itself was known to be less than six thousand years old?

The evidence for this time limit came from the Bible, which was supposed to contain a complete history of the world. By tallying all the generations and reigns of kings recorded in its pages one could estimate the total time elapsed since Creation. The answers varied, depending on which version of scripture that one used, but none exceeded six thousand years. The most definitive and precise was the one calculated by James Ussher, the Anglican Archbishop of Armagh, Ireland.

Ussher was one of the most formidable scholars of his time; it was said that his personal library was the largest in all of western Europe. He devoted his life to compiling his chronology. The date he gave for Creation was Sunday, October 23, 4004 B.C. When he died in 1656, a year after his book was published, the world would have been 5,660 years old, by his reckoning. And he believed, as did many others, that the world was not likely to get much older. Six thousand years would be the limit for the world’s total life span.

This was also revealed in the Bible, whose words were assumed to be not only history, but prophesy. The six days of Creation in Genesis foretold that the world would exist for six ages. How long was an "age"? The Bible revealed this, too. "In Thy sight, O Lord," it read, " a thousand years are as one day." Six thousand years, then, was all the time there would ever be.

For a Christian, the world could not be eternal because only God was eternal. To say that the world was eternal denied that it had a beginning, that it had been created by God, indeed that it had been created at all. People were eternal, too, in the cyclical view of time. This raised all kinds of problems. If a person could borrow money in one cycle, and repay it in the next, which some pagans saw as a perfectly acceptable practice, then where was the urgency for a sinner to reform and repay his debt to God? And the whole idea of salvation was thrown into question if the birth, crucifixion, and resurrection of Christ were not unique events in time, but happened again and again ad infinitum. "God forbid that we should believe this," wrote Saint Augustine, "For Christ died once for our sins, and rising again, dies no more."

The Bible plainly said that the world was created, not eternal. Genesis gave the story of how it happened. Some people, including Saint Augustine, allowed that the six days of Creation were probably metaphorical – although Saint Augustine thought that six days were too long for an Almighty God who could create a universe in an instant if he wanted to. But even if one was willing to add a little slack to the Creation week, the history of the world still had to be finite. Time went in one direction, it did not loop around, it had a beginning and an end.

Given the difficulty of explaining fossil seashells in a six thousand-year-old world, and the repugnance of the only apparent alternative, Aristotle’s eternal world, the idea that the fossils grew in place was understandably attractive. The flood still had its advocates – Martin Luther notably among them – and a few daring souls even dared to openly support the eternalist solution. But to argue that the seashells actually were seashells was to swim against some strong religious and scientific currents.

This, of course, is what Steno would do. And, along the way, he would offer his ideas on the growth of crystals, the erosion of land, the growth of mountains, and, most famously, the laying down of sedimentary strata. What gelled in his anatomist’s mind was a scientific approach to the anatomy of the Earth, how its parts grew and how their development could be understood. It was, in effect, a new science, sprung almost fully formed from the mind of one man.

There was no science of the Earth’s history at the time, because the Earth was not really considered to even have a history. People had a history; not things, not nature. For the orthodox Christian, each part of the world had been created in an instant, more or less in its present form. There was no point in asking how mountains or valleys formed. They had just been created. No further explanation was necessary or even possible. If someone allowed that there had, in fact, been a few changes since Creation, these were seen as inherently chaotic. Changes could only mean the decay of God’s originally perfect Creation–changes for the worse, by definition–and so not worthy of Christian contemplation. And, finally, all important events in the six thousand years since the beginning of the world were recorded in the Bible, anyway. There was no need for any further investigation.

Unlike his contemporaries, however, Steno found not chaos but order in the crust of the Earth. It wasn’t the perfectly regular order that astronomers found in the heavens, or the mathematical order that physicists found in pendulums and projectiles. It was the order of a well-told story, a narrative in which one part follows another with inevitable logic, but the conclusion is not predictable. He found the logic by which the faulting, uplift, erosion, and stratification of a landscape and the bedrock beneath it could be put into an intelligible sequence. From the narrative he read in the rocks, he could write a history of the landscape. And the logic, if extended, could reveal the history of the entire world.

The backbone of his system was a simple but tremendously powerful idea. Recognizing that the layers of rock that entombed fossil shells were made by the gradual accumulation of sediment, he realized that each layer embodied a span of time in the past. He saw no way to measure the number of years or centuries involved, and was loathe to speculate, but it was clear that the layers, one on top of the other, formed an unambiguous sequence: The lowest layer had been formed first, the highest last. Depending on their fossils and their sediments, the layers recorded the succession of seas, rivers, lakes, and soils that once covered the land. Geologists call Steno’s insight the "Principle of Superposition." It means that, layer by layer, the history of the world is written in stone.

Just as Galileo’s telescope had opened up space to science, Steno’s strata opened up the past. In an astonishing feat of intellectual focus, Steno produced his seminal geological work in a period of less than two years; two years in which his personal life also underwent major upheavals. Equally remarkable, his new science is outlined in barely 100 pages of text and just a handful of diagrams. His 78-page masterpiece De Solido (On Solids), was originally intended as an abstract, a "prodromus," of a longer and more detailed dissertation. But that work never materialized. De Solido was his last published geological work. A few years later he entered the priesthood and gave up scientific research altogether. While in Italy he had made a controversial switch from Lutheran to Catholic, and with the zeal of a new convert he devoted the remainder of his life to the Church.

Steno’s singular approach to science made him something of an enigma to his contemporaries. His abrupt retreat from it has made him an enigma to many who have studied him since. He had a mind that was extraordinarily fertile, but extraordinarily restless. And just as he overturned many assumptions about science, history, and faith cherished in his own time, his story overturns many that are equally cherished in ours.