This episode of SciShow is brought to you in
partnership with Gates Notes. You can learn more about the latest innovations
making toilets and sanitation safer, more affordable, and more
resource-efficient at gatesnotes.com. This year, they’re reflecting on progress
made over the last decade for the tenth anniversary of the “Reinvent
the Toilet Challenge.” [♪ INTRO] There are a lot of circumstances
where we wish we had a clean slate. That we could push a button
and wash all of our worries away. Today, in much of the world,
that dream is a reality… at least so far as poop is concerned. Flush the toilet and we no longer need
to worry about the bacteria and gases in sewage or the illness that we might acquire
from coming into contact with our own waste, which can be a serious problem. The World Health Organization
estimates that diarrheal diseases kill millions of people every
year, and intestinal parasites run rampant in areas without
sufficient sanitation. But across the world, and throughout
history, different peoples have developed different ways to deal with their own waste. And while they didn’t always nail the design, their efforts to keep themselves
safe have led to the toilets and sanitation systems we know and love today. So let’s take a look at some thrones
from history that show us how far we have come, and how we can still improve the
health and safety of our bathroom visits. The Mesopotamians have been credited
as inventors of the first toilet and may have been the earliest
people to have dedicated bathrooms, dating to the fourth millenium BCE. These involved pipes measuring 1
meter wide, and 4.5 meters deep, that drained to cesspits. Archaeologists have also found
toilets with brick seats and pipe with a water-repellant lining made of bitumen. Bitumen is derived from crude oil,
and today we use it in paving roads. But the Mesopotamians were
interested in other applications. It is both slippery and hydrophobic,
meaning it repels water. So waste wouldn’t stick on its way down the tube. It seems like not everyone
trusted or had access to this newfangled technology, though. Only around one fifth of Mesopotamian
households had toilets installed! However, they also understood the
importance of keeping poop far away from their living spaces. If the poop is far away, either you or
the poop would have to travel to come back into contact and make you sick. Pathogens like viruses, salmonella,
cholera, tapeworms, and more can survive and reproduce for days, months, or
even years under ideal conditions. And they can travel from poop to water, food, inanimate objects, people, or other animals. So, yeah, that’s where we get sewage pipes. You don’t just make a big pit for your
waste; you get it the heck out of there. Mesopotamian settlements Chogha
Mish in present-day Iran, Tell Asmar in present-day Iraq,
and Ugarit in present-day Syria show evidence of sewage pipes used to
transport waste outside city walls. Bitumen coating could only
do so much to keep sludge moving away from everyone’s living spaces. By around 1700 BCE, two
civilizations from different parts of the world had introduced a tool that
more effectively moved it downstream. These were the Minoans, from present-day Greece, and the Indus Valley civilization
of present-day India and Pakistan. Independently of one another,
they each created the flush. Instead of sitting over a dry
tube, these smart stinkers sat over a tunnel with water flowing through it. While both civilizations had flushing
technology and wooden toilet seats, they differed in where they
got the water supply from. Evidence from the Minoan capital city
of Knossos, in present-day Crete, suggests that the Minoans took water
from their roofs to flush their toilets. While the Indus Valley people
of Harappa, Mohenjo-Daro, and Lothal funneled water from nearby
wells into their sewage system. Either way, in both the Minoan
and Indus Valley civilizations, water would get poured down the
latrine to wash away their filth. And then, the waste would stream down into an underground sewer system to take it away. The toilet at the royal palace in Knossos
allowed for water to be poured into a separate hole that mixed with
the sewage under the seat. They even had a hole outside
the bathroom door so that someone else could flush for you! Which seems like an unnecessary
amount of luxury, even today. The flush was an innovation in moving waste away. But not everyone throughout
history nailed that concept. In fact, some of the things the Romans
thought would make them cleaner, instead may have made them sick. The Roman Empire of the first century BCE had both private and public baths spread throughout cities. But those in private homes were… a bit dangerous. They figured that a waste system for
their bodies could pull double duty as a waste system for their food scraps
and pretty much everything else. So the private toilets were usually
located very close to the kitchen, where they cooked their food. It’s likely that the Romans’ poor potty
placement led to diseases like dysentery, typhoid fever, and diarrhea, among others. On top of that, and I literally
mean on top of that, the sewers could get blocked up pretty regularly. So their waste would pile up until
the sewers could be cleaned out. That may have led to backflow
of wastewater during floods, and corresponding increases in
pests and fecal-borne disease. If that wasn’t enough, this pit of
waste in the middle of their home may have led to the
accumulation of hazardous gases. Microbes in waste can produce
flammable gases like methane. With nowhere for the waste and its fumes
to go, archeologists have speculated that from time to time, Roman
bathrooms may have caught fire. So although Romans adopted toilets
widely, they may not have been entirely effective in protecting them from
disease… and other, more unique risks. If only the Roman toilets had what
the Mayans had: water pressure. They could have used it to give that
built-up waste an extra nudge down the sewer and away from their kitchens. Minoan sewers had a series of
pipes that decreased in diameter, which increased the water pressure. But the Mayans took it to the next level. Unlike many other Mayan cities, the city
of Palenque circa 250 CE had access to an abundant supply of water for most of the year. But summer was a time of drought. And if you can’t flush when the weather
is dry, you’re not getting the benefits. So residents constructed a
limestone watershed under the city, based on natural water flow patterns. That was possible because the city was constructed over top of existing stream beds. Most Mayan cities had more
flat ground to build on, but in Palenque, they had to
create flat ground for their city. Mayan engineers constructed
narrowing conduits to keep the water under pressure. And then, they covered the conduits
to build on top of the now-open space. This underground, pressurized
chamber meant they had access to water when above-ground streams dried up. And that meant they had access to flowing
water for sanitation all year-round! By the 11th century CE, you might
think that medieval European lords in their castles would be living in luxury. But when your main source of waste
disposal is your moat, well, maybe not. If you lived in a castle, you
might have had literal poop chutes. You feel that rumble in your tummy,
head over to the tower toilet, you let ‘er rip, and gravity does the rest. Your poop would have simply fallen
down a pipe thanks to gravity, and been evacuated from the castle
and into the moat or a river, or it would just pile up in the tower. Some of those towers were
pretty tall, so just imagine the amount of waste they could contain. And this was the case in Chepstow Castle in Wales. All of the waste that collected
in and around castles could attract visitors in the form
of rodents, fleas, and lice. That’s because even though feces is a
waste product, it can still contain enough nutrients for it to be
worthwhile for animals to eat. For example, our bodies excrete an
excess amount of vitamin A via our poop. So you’ve got rats coming along to
eat the... “tasty” waste lying around. And they can become a vector for disease. Some parasites infect humans only
after infecting an intermediate host, also known as the rat in your chamber pot. And these parasites would have been
far worse than mild inconveniences. Some researchers hypothesize
that lice in medieval waste were key transmitters for the Black Plague! But folks in the Middle Ages apparently
found a way to turn their filth to their advantage. Microorganisms in feces consume oxygen, nitrogen, and phosphorus from the waste. These byproducts can react with
each other to create ammonia. And it is thought that resourceful Middle
Agers would hang their clothing near their waste chutes in the hopes that the
vapors would kill those nasty fleas. What’s more important: not having fleas
or not smelling like literal poop? Apparently not having fleas. Ok, these days, we try to keep
those disease-bearing critters away from ourselves and our waste. And there’s actually a specific technology
that keeps unwelcome smells from wafting up after you sit on the throne. It’s the S bend, or S trap. You may have noticed that
many present-day toilets have those curvy pipes either behind or inside them. Patented in England in 1775, this
extra bit of plumbing traps gases in the pipes and keeps them out of your home. The curved shape of the pipe keeps
some water trapped in the lower cradle. And that way, there’s a little
reservoir of water between you and any gases that might try to sneak up. And that’s the power of the S bend. There are also updated
versions, the P bend and U bend, which do a better job of keeping water
in the cradle and trapping gases. And in the 19th century, an English
plumber named Thomas Crapper popularized this technology with his own line of toilets. So, yeah, you can go ahead and giggle about that. It’s a pretty great name, and
it is not an urban legend. Crapper was a real guy. But the S bend, P bend, and U bend
use water to solve our problems again, and we might be using too much of a good thing. Introducing water to the waste
removal system was a huge innovation. The Minoans, the Indus Valley people,
and the Mayans all hit on that. But now we know that water
conservation is important as well. Some newer toilet designs, that are especially
popular in arid places like Australia, literally have a “number 1” and “number
2” setting, where you can determine how much water your flush needs
with the touch of a button. So what is the future of the toilet? We have an incredibly powerful
ability to communicate that we have never had before. If the Mayans could have taught the Romans
a thing or two about water pressure, maybe we’d all have better toilets today. And we know we still have more to learn. Engineers are working on things
like ways to reclaim drinkable water and produce electricity, all from human waste. Luckily, we get to build on of the progress
made by all these different peoples. Instead of piling waste on top of waste,
like early toilets did, we can pile innovations on top of innovations to move
sanitation and health into the future. If you find toilet history as fascinating
as we do, you’ll probably enjoy reading Gates Notes, the blog of Bill Gates. In fact, the “Reinvent the Toilet
Challenge” is celebrating a decade of toilet innovations this year! Humans have been finding new ways to
get rid of their waste and improve sanitation for quite a long time,
but there’s still a long way to go. The Reinvent the Toilet Challenge was
created to inspire new technologies that make safe and affordable
sanitation more accessible for communities all over the world. You can learn more about how scientists
have tackled this challenge and found ways to reinvent the toilet at gatesnotes.com. [♪ OUTRO]
