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[♪ INTRO]
Knowledge isn’t forever.
History is full of things like personal histories, languages, and even whole technologies and
techniques that we no longer remember. But one of the coolest things about archaeology
is that it gives us a chance to re-learn things.
So here are four examples of really cool technology we kind of lost,
how scientists are using modern techniques to study and re-learn them, and,
ultimately, why these techniques nearly disappeared.
One of the first examples of impressive ancient engineering is Roman concrete.
Rome built some truly epic buildings, and many of them are still around today,
like the Pantheon. Roman concrete was incredibly durable,
especially when we’re talking about its use in marine environments,
like building harbors. Building something that can last thousands
of years in wave-wracked seawater is truly impressive.
But with the decline of the Roman empire, people seem to have more or less
stopped using this super durable concrete on a wide scale.
And for a long time, we didn’t really know what made this concrete so durable.
I mean, we knew just a tiny bit. For instance, thanks to recipes
recorded by people like Vitruvius, historians knew that the Romans used
a different recipe than modern concrete. Concrete, in general, is a mix of aggregates,
like little bits of rocks or brick, water, and cement, and varying that recipe
can change its physical properties. The Romans used a particularly
involved mix of aggregate along with lime, seawater, and volcanic ash.
But not just any ash: It was a special kind called pozzolana,
which was dug up near Naples. This mix seems to be special,
since people would actually pay to import this ash when they were
building stuff. But we didn’t know
what actually made this mix special. In a study published in 2017, scientists
decided to find out. They got samples in the
form of long, cylindrical cores that had been drilled out of Roman ruins
and then used a microscope and X-rays to look at the minerals inside.
They found that the answer to the incredible durability of Roman concrete
lies in the chemistry inherent in the concrete, in large part thanks to the mix of both seawater
and that special volcanic ash. Silica and aluminum oxide from the
pozzolana reacts with lime and the seawater to create crystals of a mineral called
tobermorite, which reinforces the
concrete and makes it less likely to crack. Even better, further exposure to seawater causes
the growth of more tobermorite, explaining why Roman concrete did
so well in coastal projects. But if this was such cool tech,
how did the whole world just kind of seemingly forget about it?
Well, in this case, the answer partly has to do with demand.
In short, with the collapse of the Roman empire,
the nearby demand for this kind of mega-engineering went away.
It no longer made sense to build quite as grandly
or to pay for the special pozzolana to be dug up and shipped.
With less demand, the knowledge of how to make this concrete
started to fade away. It didn’t entirely disappear,
we have examples of engineers still reaching for pozzolana long after the Romans fell,
but it may have become more of a trade secret or kind of oral memory
rather than a codified recipe. It was only later, in the 1700s,
that science kind of formally recognized and “re-discovered” it again.
The moral is that technologies exist in context.
When it made sense for Roman concrete to be widely used, it was.
When it wasn’t, it faded into memory. Speaking of being widely used,
Roman concrete might make a further resurgence sometime soon.
A number of scientists have suggested that the formula, or something similar to it
using coal ash, might be a good candidate for marine uses today,
and produce fewer carbon emissions. Now onto something softer…Dhaka muslin
was a thin, high-quality fabric that came from what’s now Bangladesh.
It had been produced for centuries before eventually becoming a big hit in Europe
in the late 1700s. The material was made
of a special variety of cotton that grew along the Meghna River,
which had very short, easily frayed threads. This made the material kind of a beast to
work with and turning it into fabric required a convoluted, 16-step process
that would have required multiple households. One step could only be done on boats,
for instance, as the material needed to
be a certain level of humidity. The payoff of all this work,
however, was incredible. The material was very light and thin.
It was said that you could fit 18 meters of fabric into a pocket-sized snuff box and it
could apparently reach thread counts around 800-1200 threads per square inch.
But by the 1900s, it seems to have disappeared. So why’d we stop making it?
In short, because the British East India Company or EIC
made it impossible for farmers to make a profit off of it.
In the 1700s and 1800’s, the EIC effectively took over large portions of India
and started to muck with the system. One thing they did, for instance,
was to put the farmers into terrible financial situations where it was really
easy to go into irrecoverable debt. In the meantime, British manufacturers flooded
the market with inferior look-alikes. The end result was that the farmers,
no longer able to make a stable living off it, abandoned the practice.
And without people to continue growing it, the variety of cotton it was based on went
extinct. By the 1900s
Dhaka muslin was a thing of the past. That said, scientists are trying
to renew the industry. Luckily, the technique was
written down, so we do know how to make it, but we still need that special cotton.
And although it doesn’t grow anymore, we may be able to kind of recreate it.
And it’s all thanks to leaves preserved at the Kew Gardens.
Scientists could extract the DNA from those leaves
and form a genetic signature for this plant. Then it was off to the races, they started a
scavenger hunt for the closest wild plant near that one river and found one that’s a
potential cousin or descendant. Today, they've grown those plants
and are making something close to the original garments again.
So what can we learn from Dhaka muslin’s disappearance?
Again, it kind of comes down to economics, but in this case, specifically, trade and
colonialism were disrupting the industry. We can see this in other places too.
The Haya in Africa had a unique way of making a very high-quality steel
and were doing it long before many other people had the technology,
but the technique was nearly lost in the 1900s
when cheap European steel flooded the market. So, in both of the last two points,
the answer for why something was lost kind of boiled down to economics.
Sometimes, however, techniques are lost because they were too secret to spread around…
If you look at the history of warfare, one of the most mysterious
and terrifying weapons ever invented in the past was probably Greek Fire.
It was introduced by the Byzantine Greeks in the 600’s CE.
And it was described as a liquid that was discharged through a tube or grenade,
which could burn on water with thunderous noise and a lot of smoke.
There have been many proposed explanations for what this liquid could be,
but we don’t know exactly what it was because its identity was a secret.
It was a military asset, so the people who knew how to make it
probably didn’t want their enemies learning the process.
Figuring out what it may have been generally boils down to meticulous research
of existing historical records for clues and comparing proposed concoctions to see if
they match the expected properties. For instance, people have proposed
it’s based on saltpeter, kind of like an early gunpowder,
but others think it was probably based on crude or refined petroleum, something
like naphtha or napalm. In this case, the people who
made this stuff purposefully didn’t want a lot of people to know how it worked.
It’s been suggested that it may have been whipped up in a central lab,
sealed in containers, then delivered to the front lines.
So soldiers using it wouldn’t have ever known exactly how it was made.
Even if it was captured by the enemy, they wouldn’t know how to make it.
It's also been suggested that it may have been pretty complicated to actually use
and needed a whole system to make it work, like how to prep it, heat it, and use it.
If true, it's plausible that the process could have been compartmentalized,
so even if you knew part of the system, you still wouldn’t be able to
figure it all out by yourself. But the secrecy meant that the knowledge
of how to make this was tenuous. Some scholars suggest that only a
small number of individuals understood the whole system at any one given time.
And, eventually, as regimes were overturned and people died, the secret was lost.
So the reason the tech was forgotten was mainly due to secrecy.
And we can see this with a lot of proprietary or secret stuff, even today.
In the early 2000s, there was apparently a bit of a snafu when
the US military needed to refurbish their nukes,
but there were problems figuring out how to get more of a substance
codenamed “fogbank” because only a handful of records had survived
and most of the folks who knew how to make it had retired.
Now for something less terrifying. Painted on some of the terracotta soldiers
in China was an unusual, bright lavender pigment,
which we now know as Han purple. An interesting feature because at
the time it was being made, from around 800 BCE to 220 CE,
purple and blue pigments were very rare. What’s more, you can’t find this specific
pigment in nature; you have to make it. So a vibrant purple pigment that far back
in time is an incredible achievement, but Han purple didn’t stick around.
Its usage died out with the end of the Han dynasty,
around the early 200s CE, and it wasn’t rediscovered until the 1990s.
When scientists first found the pigment, they didn’t know what exactly it was.
There was no written record of how it was made,
so scientists had to rely on experimentation and analysis to find out.
To figure out what was in the stuff, scientists tried dissolving it in acid
as well as using techniques like bombarding it with X-rays under a microscope,
kind of like what the Roman concrete group did.
Thanks to these techniques, they figured out that the purple is a compound
that contains the elements like barium and copper
along with silicon and oxygen bound to it. They then experimented and found that
they could replicate it, or make something like it,
by cooking a barium mineral, such as witherite or barite, with quartz,
a copper mineral, and a lead salt. But it was a complicated technical feat
…they needed scalding temperatures of around 1000 degrees Celsius,
and had to keep up that heat for a long time. This all raises the question,
how the heck did the ancient scientists discover something this complicated?
One suggestion is that it was the result of trade and cultural exchange,
since it’s similar to another ancient synthetic pigment called Egyptian Blue,
but the logistics here seem iffy. Egypt and China are not very close to
each other geographically. Another option is that it
was discovered by glassmaking or trying to create imitation jade.
But why’d it stop being made? To be honest, we don’t know for sure.
Some researchers have suggested that, because it would have been associated
with royalty, the answer may lie in the political upheaval that spelled the end
of the Han Dynasty and the beginning of the Three Kingdoms period.
Others have suggested that, since it may have been related
to the kinds of work Taoists were doing making imitation jade,
that when Taoism became less politically important, the work kind of stopped.
Or it might be for a completely different reason altogether.
Sometimes we don’t know for sure why things disappear,
making not just the artifact, but the reason it disappeared, part of the mystery.
So, in the end, there’s a lot of stuff that we might have forgotten how to do,
like how a particular group of people brewed beer
or carved musical instruments, for instance.
And a lot of that we’ll probably never recover.
But, over the past four examples, we’ve seen how careful analysis of historical
records and samples, along with a bit of experimentation,
can help us understand not just what past people were doing, but how and why.
And by considering the question of why certain techniques were lost
in the first place, we can see how different factors can affect technology.
One way to keep from losing techniques is to keep notes and save them in a file.
And if you’re worried about someone gaining access to your proprietary technique,
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[♪ OUTRO]