In 1676, a Dutch textile trader with a strong fascination for microscopes, Antony van Leeuwenhoek, uncovered microbes and initiated their categorization. Two centuries afterward, a German physician in present-day Poland, Robert Koch, recognized the anthrax bacterium, marking a pivotal advancement towards contemporary germ theory. These remarkable breakthroughs, alongside others, have contributed to the foundation of modern existence as we understand it.
Indeed, germ theory has fostered medical progress that significantly curtails fatalities from infectious ailments. In the U.S. during 1900, the primary causes of death included pneumonia, influenza, tuberculosis, and gastrointestinal infections, collectively accounting for nearly half of the country’s mortality rates. Moreover, throughout much of civilization until the past fifty years, childhood was an exceedingly uncertain time due to the danger posed by diseases.
“The era we’ve known since the 1950s, and especially the 1970s, is unmatched in human history,” states MIT Professor Thomas Levenson. “Consider all the grandparents able to participate in their grandchildren’s weddings who otherwise may not have survived, as either they or the children could have succumbed to these diseases. Human progress has arisen from this extraordinary scientific evolution.”
For Levenson, two aspects of this historical path stand out. One is that it required 200 years to establish germ theory. The other is our capability to fight these ailments so effectively — something he feels we should cherish.
In his new book, “So Very Small: How Humans Discovered the Microcosmos, Defeated Germs — and May Still Lose the War against Infectious Disease,” published by Penguin Random House, Levenson examines these topics, weaving a historically rich narrative that resonates today. In discussing the evolution of germ theory, Levenson aims to shed light on “the single most lifesaving innovation that human creativity has ever produced.”
A 200-year incubation phase
The foundation of Levenson’s inquiry was the straightforward observation that van Leeuwenhoek’s discovery — coupled with his illustrations of microbes identifiable today — did not prompt tangible advancements for an extensive period.
“It’s almost precisely 200 years from the identification of bacteria to the clear proof that they impact our existence in life-and-death situations,” states Levenson. “Infectious disease is a significant issue, yet it took two centuries to recognize it. I wanted to understand why.”
Among various obstacles, numerous ideas, often relating to societal structures, hindered progress. The prevalent belief in a “great chain of being” diverted attention from the concept that microorganisms could influence human well-being. Nevertheless, some individuals acknowledged the potential that tiny organisms might transmit illness. In the late 1600s, Puritan minister Cotton Mather speculated whether certain “animacules” could each be accountable for different pathogens.
As the 19th century unfolded, a handful of isolated thinkers recognized the importance of microbes in the transmission of infectious illnesses, yet their concepts failed to gain much support. An 18th-century physician in Aberdeen, Scotland, Alexander Gordon, linked the spread of puerperal fever — a disease that fatal to new mothers — to substances doctors and midwives might carry on their hands during childbirth. A few decades later, a physician in Vienna, Ignaz Semmelweis, concluded that doctors conducting autopsies were transmitting illness to maternity wards. However, skeptics questioned whether respectable physicians could be carriers of illness, and for years, little was done to curtail infection transmission.
Ultimately, as Levenson recounts, more scientists, particularly Louis Pasteur in France, gathered sufficient evidence to establish bacteriology as a discipline. Medicine progressed through much of the 20th century to such a degree that, in the post-war period in the U.S., vaccines and antibiotics drastically reduced human mortality and distress.
Ultimately, the acceptance of new concepts, such as microbes causing illness, is influenced by “the strength of cultural assumptions and the hierarchical fabric of society,” Levenson remarks. “If you believe you’ve demonstrated that doctors can spread infections from one patient to another, but others are unable to adopt this insight due to different beliefs, that explains why it took so long to arrive at germ theory. Scientific facts may eventually prevail, but such an outcome can be delayed.”
He further notes: “This can occur when a solution becomes intertwined with factors unrelated to science.”
Science and society
Recognizing that entanglement between science and society is a fundamental element of “So Very Small,” as well as in Levenson’s numerous other writings. Science rarely exists in isolation from society. The question is how they influence one another in any given context.
“One of the themes of my work is how science truly functions, as opposed to how we are told it operates,” Levenson explains. “It’s not merely a continuous iterative mechanism generating new knowledge and hypotheses. Science is a vast human enterprise. The individuals engaged in it possess their own beliefs and cultural biases, and are part of larger societies they interact with constantly, which also possess their unique traits. These factors significantly influence what science achieves and how it does so. And this remains relevant today.”
Certainly, infectious diseases have never completely vanished from history. Some still prevail in developing nations, while the Covid and HIV/AIDS pandemics are instances where novel medical solutions needed to be established to combat emerging illnesses. Nevertheless, as Levenson points out in his book, the interplay of science and society may create further uncertainties for us in the future. Antibiotics can diminish in effectiveness over time, for instance.
“If we aspire to develop new antibiotics capable of combating bacterial infections, we must invest in their research, marketing, and regulation,” Levenson asserts. “That is not a political assertion. Bacteria behave as they do; they evolve in response to challenges.” Simultaneously, he observes that although “there has always been [human] resistance to vaccines,” the increased prevalence of this resistance today raises new issues concerning how widely vaccines will be accessible and utilized.
“So Very Small” has received overwhelmingly positive reviews in leading outlets. The Wall Street Journal noted that “With remarkable detail and authoritative prose … What Mr. Levenson’s book clarifies is that the struggle against germs is unending.” The New York Review of Books described it as “an elegant, comprehensive history of the discovery of microorganisms and their connection to diseases.”
Ultimately, Levenson concludes, “Science provides us with the material power that propels societal changes, shaping history, and science is conducted by individuals situated within specific contexts. Examining this is a delightful way to engage with broader inquiries. That holds true for germ theory as well. It reveals much about societal values and scrutinizes the society in which we currently reside.”