The Universe Within (13 page)

This answer led to a whole new puzzle. The more Barghoorn looked at Tyler’s slides, the more ancient species he saw. Each sample was brimming with algae spores, filaments, and the remains of thousands of single-celled animals. The basement of rock on our planet wasn’t devoid of life but teeming with it.

Now the “inexplicable mystery” lay not in the missing life but in understanding the plethora of living things that were once hidden from our view. When did life get its start on the planet? What did the earliest living things look like? Because there was a world of questions to ask and creatures to find, a new kind
of paleontologist emerged—one whose life’s goal was to recover microscopic fossils from rocks billions of years old.

Hunting for fossils in the first 2 billion years of Earth’s history has special challenges. Rocks of the right type to hold super-ancient fossils are likely to have been eroded away, baked by internal heat, or transformed by various movements of Earth’s crust. Let’s say you actually manage to find ideal rocks. How can you tell that a microscopic bleb or filament was once a living thing and not some mineral or inclusion in the rock? The science of early life is one of constructing multiple lines of evidence, from the shape and structure of the putative fossils to the chemistry of the rocks that hold them. The hunt is for creatures that not only look like single-celled forms but also reveal the chemical workings of metabolisms.

With this playbook, Stanley Tyler, Elso Barghoorn, and their scientific descendants exposed the hidden reality inside the rocks: the earliest fossils are now known to be over 3.4 billion years old. Life arose early in the history of our planet and, once off to that start, expanded rapidly to become a menagerie of different kinds of
bacteria, algae, and their relatives.

Despite their incredible diversity, the organisms that dominated the first billions of years of the history of our planet share one important thing. They are all single celled and microscopic. Some of them lump together to form colonies, but no individual dwelling on Earth for the first 3 billion years was larger than a grain of rice. Big, in the world of living things, had yet to come about.

“That one’s dead,”
Thomas
Barbour, the director of Harvard’s Museum of Comparative Zoology, shouted while considering a frog lying motionless on the grass in front of him.

On the roof above Barbour stood his colleague Professor Philip Darlington, holding a bucket of frogs with one hand. With the other, he was pitching the frogs one by one onto the lawn five stories below.

Barbour nodded as each frog hit and remained motionless in the grass below his feet. When Darlington descended with his empty bucket, he asked Barbour how the animals withstood the impact. Seeing the frogs strewn about, Barbour offered, “All dead.”

Darlington was a naturalist of the old school: when he wasn’t teaching courses at Harvard College, he was off in the jungle collecting new species, beetles in particular. Tales of his days in the field are legendary, including the time he was grabbed by a
crocodile, pulled to the bottom of a stream, and, as the crocodile began to consume him, kicked himself free. Hiking miles to safety with shredded legs and hands, he wrote to his wife later that night only that he had an “episode with a crocodile.”

In the midst of his explorations in the 1930s, debates were raging about how animals dispersed to new places around the globe. This was the era before
plate tectonics, and there were two major ways to explain
animal distributions: either there were land bridges between continents—now lost—that allowed animals to walk from place to place, or animals could be blown by wind, water, and storm. Darlington was a firm believer in the latter and his boss, Thomas Barbour, in the former.

The frog “experiment”—something we would obviously never perform today—began as an argument. During coffee at the museum one afternoon, the two got into a tussle about the theories and made a wager. Barbour held that dispersal by wind was impossible because animals would die upon impact. Darlington countered that wind dispersal would work over considerable distances for small animals. The two agreed on the rooftop test of the theory.

And what of Darlington’s dead frogs?

Within minutes after the impact, each frog arose and hopped away. Soon the grass was filled with frogs bounding in different directions. Darlington proved his point.

Of course, there is nothing unique about frogs that allowed them to survive such a fall; this ability is a reflection of their size. Small animals accelerate more slowly during a fall than do large ones, since they experience more air resistance for a given
mass. In describing this phenomenon,
J. B. S. Haldane, one of the founders of evolutionary
genetics, said, “You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away.… A rat is killed, a man is broken, a horse splashes.”

Let’s say you want to
predict what an animal can do—how long it lives, how it moves about—and what it looks like without ever having seen it. A number of factors may be influential: the kinds of foods the creature eats, where it lives, where it sits in the food chain, and so forth. People have explored this issue by cataloging measurable traits that creatures possess and hitting the data with a number of different statistical tools to gauge which measurement accounts for the differences we see. In analysis after analysis, one factor reigns supreme in its predictive power—size. Know a creature’s size, and you can make educated guesses about much of its biology, including its resting heartbeats per minute (smaller animals have higher heart rates), its perception of danger (larger animals have less fear), even its life span (in general, larger means longer).

Virtually every part of the world we experience is influenced by our size, even how we visualize size itself. The size and shape of our pupils, eyeballs, and lenses influence our visual acuity just as the shape and structure of the different components of our ears affect the sound frequencies we hear. Because ours is a world tuned to the predators, prey, and other entities of our ancestors’ worlds, we are like a radio that can receive only a small number of channels; vast portions of the world remain hidden
to us. Extending our gaze beyond the limitations of our biology has meant seeing our size, and ourselves, in a brand-new light.

Anton van Leeuwenhoek (1632–1723) spent much of his career as a draper and found himself needing to develop magnifying glasses to assess the quality of his fabrics. Becoming fascinated by the properties of glass, he manufactured new kinds of lenses that magnified objects many times beyond the tools common to his trade at the time. He tweaked the shape of the glass again and again, each time seeing smaller things, ultimately magnifying objects two hundred times. With each new lens he crafted, he was exploring a new world.

Van Leeuwenhoek was famously secretive about how he crafted his lenses. For centuries it was thought that he polished the glass into ever-finer slivers. Then, in 1957, a science writer for
Scientific American
speculated on van Leeuwenhoek’s trade secret: he made his lenses by heating glass rods and pulling them apart. Reheating the broken end made a little ball at the tip. When this little glass bead was separated from the rod, he mounted it in a mechanical contraption that held both the specimen and the bead at a set distance. Peering through the glass bead revealed its magnifying properties, and the bent glass served as a kind of lens.

Everything became fodder for van Leeuwenhoek’s
microscope. In one famous experiment he took the plaque from an older gentleman’s mouth and put it in his scope. In it, van Leeuwenhoek found “an unbelievably great company of living animalcules, a-swimming more nimbly than any I had ever seen up to this time.… Moreover, the other animalcules were in such enormous numbers, that all the spittle … seemed to be alive.” This is thought to be one of the earliest known descriptions of
bacteria. He looked at pond water and found a carnival of life inside—from algae to microbes—and later described human semen as containing little tadpole-like creatures.

People flocked to see van Leeuwenhoek’s cabinet of wonders in his house in Delft. There, they became the first humans to
catch a glimpse of a novel world. For thousands of years all of human knowledge was centered on the universe we can hear, touch, and see with our natural-born senses. By extending beyond our biological inheritance, van Leeuwenhoek revealed we are all big creatures living in a world chock-full of innumerable
microscopic ones.

Just a few decades before van Leeuwenhoek’s revelations with a microscope,
Galileo Galilei (1564–1642) was doing the exact opposite: grinding glass to make a telescope. With the most powerful telescope of his day, equivalent to a large set of binoculars from an outdoors store today, Galileo was able to see Venus’s
phases, that Jupiter had
moons rotating around it, and that huge
nebulae populate the sky.

Van Leeuwenhoek looked down through a microscope to find a small world. Galileo looked up to the sky and revealed a huge one, with incomprehensibly large planets and vast distances. In van Leeuwenhoek’s world, we are humbled by the diversity of microscopic life beneath our noses and within our bodies; in Galileo’s, by the sheer size of the world around and above us.
How did this new humility come into being? By finding new ways to use glass.

Around 1633, over twenty years after
Galileo constructed his telescope and described the rotation of the bodies of the solar system, he was found guilty of heresy and sentenced to be imprisoned for the remainder of his life. Because he was already seventy years old, he was placed under house arrest, first in Siena and later in his own home in Florence. During this period of confinement, Galileo spent about five years writing about physics. He was forbidden to publish in Italy, so a Dutch printer,
Louis Elzevir, secreted his manuscript out of the country.

Galileo’s book—different from any science exposition we are familiar with today—consists of a fictional conversation among three men who set out to explore the fundamental laws of the universe. Their conversation holds the beauty of mathematics applied to the world around us.

On day two of the confab, the three explore the laws that govern the shapes of all objects. What happens to objects when they get bigger? How do small objects differ from big ones? Think of
trees: short trees can get by with relatively narrow trunks, but tall trees are an entirely different matter. Assuming the properties of the wood are the same, tall trees will need proportionally wider trunks to protect them from bending and breaking. This simple relation between size and shape defines much of the world around us. A lithograph of upper leg bones from Galileo’s book reveals it all. A mouse femur and an elephant femur are similar in many ways, because they have the same joints, and they are composed of similar bones. But the elephant femur is proportionally much wider than that of the mouse. Just as with the tree trunks, larger size necessitates new shapes. This relationship holds for dinosaurs and elephants as much as it does for bridges and buildings. And the reason, as Galileo recognized, is because larger entities have to deal with ever-increasing effects of gravity.