Is This The Biggest Mistake Science Ever Made?
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DownloadWe’re pretty solid on germ theory at this point.
The idea that many diseases are caused
and spread by pathogens too small to seen
has been locked in since the mid 19th century.
But that wasn’t the first time people came up with those ideas.
Physicians around the world had been theorizing
about the spread of infectious disease through invisible particles
as early as the 9th century.
That’s one thousand years earlier.
These scholars did everything they could to limit the spread of infection
and understand how it worked.
But if we had the basis for germ theory …
by all accounts a correct idea …
why did it take so long for it to actually take root?
Well, because right ideas don’t always win – not right away.
And sometimes wrong ideas can be pretty convincing.
So let’s take a look at why one of the most important ideas in biology
took centuries to accept.
[intro music]
Before germ theory, the main idea behind the spread of diseases was called miasma theory.
Miasma theory says that you catch diseases from bad air,
so anything that smelled bad or rotten was the reason you’d get sick.
In some ways, it makes sense why people believed this.
Places that are crowded and smelly do also tend to be hotbeds of disease.
Although we now know it’s because of the viruses and bacteria
that come with waste and crowded areas, not the air itself.
It just so happened that many of the prevention methods
against miasma
also prevented the transmission of disease from germs.
For example, people got rid of “bad air”
by swiftly removing waste and dead bodies from populated areas,
which is still an important way to prevent disease transmission
in the modern era.
But around the time of the Black Death in the 1300s,
it became clear that miasma theory was not enough to explain the spread of disease.
Some people looked for explanations to augment miasma theory,
including that the celestial energies of Mars and Jupiter
were drawing up toxic air from the earth.
And you thought Mercury being in retrograde was bad…
But some people had another idea.
They started thinking that diseases
might actually come from something other than the air:
a contagion.
Some European cities started implementing quarantines on incoming ships
to make sure that sailors weren’t bringing in any diseases with them.
That’s not to say that everyone was suddenly Team Contagion now.
But as the Black Death continued to devastate Eurasia,
people began to put more contagion-based ideas together with miasma.
Some doctors thought that while the body
could make more of a disease and spread it to others,
miasmas were what caused the initial illness.
In fact, the classic plague doctor mask was born from miasma theories
during the Black Death.
The iconic beak shape was created to store sweet-smelling things
for the doctors to breathe instead of the stinky, sick air,
and it included spices like cinnamon and myrrh.
Oh, and ground up vipers. Just for funsies.
This wasn’t even the first time in history
that people were combining miasma and contagion theories.
In the ninth century, a scholar named Qustā ibn Lūqā
hypothesized that some diseases were spread by foul air,
and others by a spark of illness that can jump from a sick person to a healthy one.
In 1546, an Italian physician named Girolamo Fracastoro
published the first known work proposing a fully contagion-based theory of disease.
Despite having no knowledge of microbes,
he theorized that diseases were spread by so-called “seeds”
that caused illness when they came into contact with people.
Fracastoro started his disease studies by looking at syphilis and animal outbreaks.
He noticed that syphilis
seemed to pass primarily from person to person through sexual contact,
and sick animals would get the entire herd sick
if they weren’t isolated.
After reading a poem that described invisible seeds floating through the air,
some fostering life and others creating disease,
Fracastoro found his analogy for contagion.
Never let anyone tell you that scientists don’t need to study the arts.
Fracastoro hypothesized that seeds of disease were all around us,
and they could multiply inside a host before spreading to other people.
They could spread through direct contact, like syphilis,
they could float through the air,
or they could be passed from person to person
through a contaminated object.
He coined the term fomites for these surfaces
that can pass on disease from one person to another, and we still use that term today.
Even though Fracastoro got many things shockingly spot on,
his ideas were mostly passed over for 300 years.
In good scientific fashion,
he presented his thoughts on seeds and contagion to his peers,
who debated and ultimately rejected it.
And it’s not that his colleagues were being unscientific
by rejecting his ideas.
At this point, Fracastoro was simply hypothesizing,
and he didn’t do any experiments to back up his claims.
It’s funny how things that we may take for granted now,
seemed like wild, half-baked ideas back in the day.
I mean, really.
Imagine our world full of tiny little dudes,
completely self sufficient and self replicating and living complex lives,
then wiping out the human population on the side.
Oh, and they’re invisible by the way.
Come on! Why would you think that when stinky air
is literally right there under your nose?
Science needed the proof of actually seeing
a whole hidden world of microorganisms
in order to accept Fracastoro’s ideas for what they were.
It’s not really Fracastoro’s fault.
He couldn’t do the experiments that his theory so badly needed.
It wouldn’t be until decades later that the first microscope was invented,
then another hundred-ish years for Antonie van Leeuwenhoek
to observe bacteria for the first time.
Even as more and more people started to buy into contagion theories,
it would still take more convincing for scientists
to fully hop on the contagion bandwagon.
Around the 18th century,
people started to split into two camps of disease theory,
and like all good rivalries, they got team names.
You have contagionists,
who were backing the idea that disease is caused by microorganisms,
and you have miasmatists,
who were backing the idea of, well, miasma.
Since miasma was already the dominant worldview,
contagionists had the burden of proof.
A lot of early contagionist ideas
were able to be explained away by miasma,
and coincidences,
like patients surviving ineffective miasma-based treatments,
fed into the preexisting beliefs.
Contagionists needed clear proof to sway the scientific community,
and throughout all this time,
they still didn’t have anything to point to
as a clear cause-and-effect from a germ to a disease.
The proof took all the way until the late 1800s,
when Robert Koch isolated anthrax bacteria from cows to infect mice,
who then got anthrax and died.
This experiment confirmed what Fracastoro
and so many others had suspected all along:
germs cause disease, not bad air.
From there, germ theory really took flight,
and a thorough series of experiments during the early 1900s
finally settled the debate.
Even if Fracastoro was just spitballing at the time,
he was vindicated eventually.
Science is a process, and sometimes that process…
takes a while.
But it’s a process that helps ideas rise to the top
when they’re supported by evidence.
And thanks to germ theory,
we have vaccines and huge advances in public health… finally.
This video was inspired by Air-borne, a new book by Carl Zimmer.
It’s a history of airborne disease and how it has shaped the world.
If you’d like to check it out, head to the SciShow Bookshop page.
This video was made possible
by the Alfred P. Sloan Foundation.
[ OUTRO ]
Key Vocabulary (50)
toward
"Go to school."
belonging
"Cup of tea."
also
"You and me."
inside
"In the house."
specific
"That book."
A third-person singular pronoun used to refer to an object, animal, or situation that has already been mentioned or is clear from context. It is also frequently used as a dummy subject to talk about time, weather, or distance.
Used to show who is intended to have or use something, or to explain the purpose or reason for an action. It is also frequently used to indicate a specific duration of time.
A function word used to express negation or denial. It is primarily used to make a sentence or phrase negative, often following an auxiliary verb or the verb 'to be'.
A preposition used to indicate that something is in a position above and supported by a surface. It is also used to indicate a specific day or date, or to show that a device is functioning.
A preposition used to indicate that people or things are together, in the same place, or performing an action together. It can also describe the instrument used to perform an action or a characteristic that someone or something has.
A pronoun used to refer to a male person or animal that has already been mentioned or is easily identified. It functions as the subject of a sentence.
A conjunction used to compare two things that are equal in some way. It is most commonly used in the pattern 'as + adjective/adverb + as' to show similarity.
Used to refer to the person or people that the speaker is addressing. It is the second-person pronoun used for both singular and plural subjects and objects.
A preposition used to indicate a specific point, location, or position in space. It is also used to specify a particular point in time or a certain state or activity.
Used to identify a specific person, thing, or idea that is physically close to the speaker or has just been mentioned. It can also refer to the present time or a situation that is currently happening.
Description
Check out Air-Borne: The Hidden History of the Life We Breathe by Carl Zimmer at https://bookshop.org/lists/scishow-recommended-reading. This video was made possible by the Alfred P. Sloan...
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