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 millennium 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, archaeologists 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].