Per the suggestion of a friend, albeit one that came about three weeks ago, I’ve decided to write an entry about how theories can be supplanted when new ones that make more sense and come with more evidence are proposed. I feel that this draws parallels to the world of politics, where changing your mind based on new information is viewed as “flip-flopping”, whereas if you never change your mind, you are a “strong leader.” The comic Bizzaro did a nice job of illustrating this once, but I can’t find a link to it.
Anyway, as an example of my above point, let’s discuss the Miasma theory of disease, and how it has been supplanted by the germ theory. (Quick definition of theory = “comprises a collection of concepts, including abstractions of observable phenomena expressed as quantifiable properties, together with scientific laws that express relationships between observations of such concepts” (from Wikipedia page on scientific theory.)
The Miasma theory of disease holds that many diseases such as chlamydia, cholera, and even Black Plague were caused by bad/polluted air. (Miasma come from the Greek for “pollution.”) Perhaps one of the best-known instances of the miasma theory being put into large practice is in the cholera outbreaks of the 1850s in London. Until John Snow deduced in 1854 that cholera was being spread via the dirty water in the London slums, the theory that it was being spread by dirty air was the going idea. This idea even made acceptance of Snow’s theory difficult, and prevented sanitary measures from being introduced in a timely fashion.
Florence Nightingale was also a big proponent of miasma theory. That doesn’t discredit her work, however, because due to her strong belief that bad air was causing various infectious diseases, hospitals became more and more sanitary. (And started to smell better!) Others who accepted miasma theory made the connection between dirtiness and disease, but they did not understand that it was the germs in that dirtiness that was actually making people sick.
Enter germ theory. This theory, like many in science, was highly controversial when it was proposed. (Imagine that, controversy in science…) I can definitely see why though: “Wait, so you doctors are telling me that what’s making me sick are these tiny little things that I can’t see and that live inside of me?” Kind of hard to believe, right?
Germ theory is actually much older than Anton van Leeuwenhoek and Louis Pasteur. An ancient Hindu text called the Atharvaveda mentions living agents as the cause of disease. In 36 BC, On Agriculture was published, and in it a warning about locating a home near a swamp, due to minute organisms that can float through the air and cause sickness.
It wasn’t until 1676 that the first of many scientists (van Leeuwenhoek) made the first crucial discovery that would go on to help prove germ theory: observing bacteria under a microscope. That proved the existence of microorganisms. Ignaz Semmelweis contributed to the theory in 1847, by lowering child mortality rates at a Vienna hospital after making doctors wash their hands between autopsies and delivering a child. John Snow, with his observations about cholera, added more evidence. Pasteur, between 1860 and 1864, added even more backing with his evidence against spontaneous generation of bacteria.
Robert Koch, in 1890, really added the final blow against miasma theory, and gave the best weight to germ theory with his postulates. These 4 rules, with following experiments, essentially proved germ theory (and are still used today in the study of new diseases):
- The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy animals.
- The microorganism must be isolated from a diseased organism and grown in pure culture.
- The cultured microorganism should cause disease when introduced into a healthy organism.
- The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
Germ theory has supplanted miasma theory because it has been tested many times, has a large body of evidence behind it, and is frankly the more logical explanation. The practice of germ theory has resulted in antibiotics and sterile treatments (thank you Lister), and is now a cornerstone of clinical microbiology. Only delusional people still believe miasma theory. 🙂