The Universe Within by Neil Shubin Page B

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 hiddento 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’smicroscope. 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 ofbacteria. 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 tocatch 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 innumerablemicroscopic ones.
    Anton van Leeuwenhoek and his microscope. (Illustration Credit 5.2)
    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