The diseases that changed humanity forever - Dan Kwartler
Since humanity's earliest days,
we’ve been plagued by countless
disease-causing pathogens.
Invisible and persistent,
these microorganisms
and the illnesses they incur
have killed more humans
than anything else in history.
But which disease is deadliest
varies across time and place.
Because while the march of progress
has made us safer
from some infectious threats,
human innovation often exposes
us to surprising new maladies.
Our tour of history’s
deadliest diseases begins
when humans lived in small
hunter-gatherer communities.
The illnesses these pre-agricultural
nomads encountered
most likely came from the various
animals they ate,
and the soil and water
they interacted with.
There are no written records to help
us identify these diseases,
however, some illnesses leave distinct
growths or lesions on the skeleton,
allowing bioarchaeologists
to diagnose ancient remains.
And researchers have found
that bones from this era
suggest the presence of tuberculosis
and treponemal infections.
While these conditions
are life-threatening,
the deadliest diseases are invariably
part of widespread epidemics,
and there’s no evidence
of any large-scale outbreaks
in this lengthy pre-agricultural period.
However, when humans started developing
agriculture around 12,000 years ago,
it brought a whole new crop of diseases.
Early farmers knew little about
waste and water management,
setting the stage for diarrheal
diseases like dysentery.
Much worse, the proliferation
of open fields and irrigation
created standing pools of water which
brought mosquitoes and in turn malaria—
one of history’s oldest
and deadliest diseases.
We don’t know exactly how many
early farmers malaria killed,
or how many it left vulnerable
to other lethal infections.
But we do know this mosquito-borne illness
continued to spread
through humanity’s next major development:
urbanization.
In small communities,
infectious diseases like measles
and smallpox can only circulate so long
before running out of hosts.
But in densely populated regions
with high birth rates,
fast-evolving viruses like the flu can
continually infect new individuals
and morph into various strains.
When large settlements became common,
medical science hadn't advanced
enough to effectively treat
or even distinguish these variants.
Nor was it prepared to deal with one
of the deadliest pandemics of all time:
the Black Death.
From the 1330s to the 1350s,
the bubonic plague
swept Asia, Africa and Europe,
reducing the global population
from 475 million to roughly 350 million.
Like most Afro-Eurasian diseases,
the plague didn’t cross the Atlantic
until Europeans did in the late 1400s.
But at the height of the plague
in Europe, Asia, and North Africa,
infection was almost guaranteed,
and the plague’s fatality rate
ranged from 30 to 75%.
However, the illness wasn't equally
distributed among the population.
Many wealthy lords and landowners were
able to stay safe
by hiding away in their spacious homes.
As medical knowledge became more robust,
this kind of class disparity began
reflecting who had access to medical care.
And that divide became particularly
apparent during the reign
of our next deadly disease.
By the beginning of the 19th century,
tuberculosis was already one
of the most common causes of death
in Europe and the Americas.
But the Industrial Revolution led
to working and living conditions
that were overcrowded
and poorly ventilated,
turning TB into an epidemic that killed
a quarter of Europe’s adult population.
The unhealthiest environments were largely
populated by impoverished individuals
who often went untreated,
while doctors provided wealthier victims
with the era’s most cutting-edge care.
Throughout the 20th century, vaccines
became common in many countries,
even eradicating the centuries-old
viral threat of smallpox.
The advent of vaccination,
alongside improvements
in nutrition and hygiene,
have helped people live longer
lives on average.
And today, medical advances
in rapid testing and mRNA vaccines
can help us tackle new outbreaks
in record time.
However, countless regions
around the world
remain unable to access vaccines,
leaving them vulnerable to older threats.
Malaria still takes the lives
of over 600,000 people every year,
with 96% of deaths occurring
in communities across Africa.
Tuberculosis continues to infect millions,
almost half of whom live
in Southeast Asia.
Addressing these ailments
and those yet to emerge
will require scientists to develop
new and more effective medicines.
But something governments and health care
systems can do today
is working to make the treatments we have
already accessible to all.
