Ancient Imaginations of the Microbial World

May 27, 2017

Marcus Terenzio VarroneFigure 1. The Roman scholar Marcus Terentius Varro. Source.

There is one force that advances even more rapidly than human technology. That force is the imagination. In 1916, Albert Einstein imagined invisible ripples in the fabric of the universe that travel at the speed of light. These “gravitational waves” were not measured experimentally until 2015. In 1964, Peter Higgs theorized the existence of what we now call the Higgs boson, one of the elementary particles that makes up matter. It took five decades, 10,000 scientists and $13 billion to confirm its existence using the Large Hadron Collider. Likewise, ideas about microbial life began over 2,000 years before before Antoni van Leeuwenhoek discovered microbes.

Ancient cultures developed practices based around microbes long before microbial cells were visualized using a microscope. In 400 BC, the Greek physician Hippocrates wrote about fevers caused by “unwholesome” air found in marshy areas containing stagnant water. The idea that marsh or swamp air transmitted mysterious contagions continued during the rise of the Roman empire. Roman generals positioned army camps far away from swamps to avoid disease among soldiers. Experiments in Roman battlefield medicine also led surgeons to clean tools and bandages in boiling water before each use. Among the first sterile techniques, this practice promoted healthy wound healing even though there was no way of understanding how or why it worked.

In 30 BC, the Roman scholar Marcus Terentius Varro was among the first people to explicitly write about imaginary microscopic creatures in the air. In his series of books, Rerum Rusticarum Libri Tres, or Three Books On Agriculture, Varro wrote that “Precautions must also be taken in the neighborhood of swamps … because there bred certain animalculae which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there cause serious diseases."  Varro’s passage in On Agriculture marked the point in history when humans had advanced far enough in scientific thinking to formulate the concept of microbes.

Plasmodium drawingsFigure 2. The first drawings of the Plasmodium parasite, identified by Alphonse Laveran as the the causative agent of malaria or “marsh fevers“ in 1880. Source.

The fear of dangerous air continued for many centuries until the true causative agent of marsh fever was identified. In the Middle Ages, dangerous vapors carried by air were known as miasma. Another now familiar term for the cause of marsh fever emerged in medieval Italy in 1560: mal aria, meaning bad air. Eventually, air-based theories of disease were superseded by germ theory in the 1800s. By then well into the age of the microscope, the parasite carried by mosquitoes was identified by the French physician Alphonse Laveran in 1880. Laveran sent early drawings of the parasite (that he would later name Plasmodium) in notes to the French Academy of Medicine with the subject, "New Parasite Found in the Blood of Several Patients Suffering from Marsh Fever." By the end of the 19th century, mosquitoes were found to be the transmitting vector of the parasite. The ancient link between disease and marshes was finally complete: mosquitoes require standing water to complete their lifecycle and therefore they flourish and transmit Plasmodium to their hosts at high rates near swampy areas. At last, Marcus Varro’s foreshadowing of harmful microbes in swamps from 30 BC was verified.

Einstein famously stated that “Imagination is more important than knowledge.” Knowledge, he said, “is limited to all we know and understand, while imagination embraces the entire world, and all there ever will be to know and understand.” Today, microbes are so foundational to biology that we take what was once imaginary for Marcus Varro for granted. However with respect to many other scientific subjects, we are today much like Varro was in 30 BC. We imagine that we might live in a multiverse of many or perhaps an infinite number of universes, though we cannot observe any light beyond our universe. We imagine alien microbial life on Jupiter’s icy moon Europa, though we have not been there to collect a sample. And we are doing our best to reverse engineer the chemical origin of life on Earth billions of years ago, though no one was around then to observe it. Imagination will always be the leading edge of human exploration.

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Author: Scott Chimileski

Scott Chimileski
Senior Contributor Scott Chimileski is a Research Fellow in Roberto Kolter’s laboratory at Harvard Medical School.