Full transcript
0:00It's noon in Thebes. It's 1350 BCE and
0:04it is conservatively 43° C. That's 110°
0:09F for the Americans in the audience.
0:11There is no air conditioning. There is
0:13no ice. There is no cold drink of any
0:16kind anywhere on the planet because
0:18refrigeration will not be invented for
0:20another 3,000 years. You are standing on
0:23sand that is hot enough to cook an egg
0:24on in a country that is 95% desert
0:27wearing a linen kilt and you are about
0:30to go do manual labor and you're fine.
0:32Not fine as in miserable and coping.
0:34Fine as in this is a normal Tuesday.
0:36Fine as in you will do this again
0:38tomorrow and the day after and you will
0:40live to be 60, which for the ancient
0:43world is the oldest anyone lives. Now,
0:46here's what I want you to sit with. We
0:47look at ancient Egypt and we see the
0:49pyramids. We see gold masks and mummies
0:52and Tutankhamun's face on a museum
0:54poster. What we never see is the boring
0:56relentless daily engineering problem
0:58sitting underneath all of it. How do you
1:00keep several million people alive,
1:02working, and not dying of heatstroke in
1:04one of the hottest inhabited places on
1:06Earth for 3,000 years with no
1:07electricity? Because that's the actual
1:10achievement. Anybody can build a big
1:11triangle if they've got enough rocks and
1:13enough time, but keeping the workforce
1:15alive long enough to finish it, that's
1:17the hard part. So, today we're going
1:19through all of it. The architecture, the
1:21clothing, the beer, the salt, the wind
1:23catchers, the doctors, the beard
1:25situation. And by the end you're going
1:27to realize something slightly
1:28uncomfortable. The Egyptian solved this
1:30problem so well that we've spent the
1:32last century solving it worse, just with
1:34more electricity. Let's go. The thing
1:37nobody tells you about Egypt. Here's the
1:39misconception baked into the question
1:41itself. We picture ancient Egyptians
1:43enduring the heat, suffering through it,
1:46grimly surviving, like the desert was an
1:48enemy they held off by sheer willpower
1:51and stubbornness. That's wrong and it's
1:53wrong in an interesting way. The
1:55Egyptians weren't surviving the desert.
1:57They were living in a very narrow green
1:59ribbon next to the desert, and they had
2:01spent thousands of years engineering
2:03that ribbon so thoroughly that the heat
2:04became a design parameter rather than a
2:07threat. Every single thing about
2:09Egyptian daily life, the shape of the
2:11houses, the fabric of the clothes, the
2:13timing of the work day, what you drank,
2:15when you ate, which direction your bed
2:17faced, all of it had been quietly
2:19optimized over dozens of generations to
2:21deal with one specific problem. They
2:23weren't fighting the sun. They'd made
2:25peace with it and then read the fine
2:27print very carefully. And to understand
2:29how, we need to talk about the least
2:31glamorous topic in Egyptology, sweat.
2:35You are a walking evaporation machine.
2:37Your body has exactly one serious
2:39cooling strategy, and it's water. When
2:41you get hot, you push water through your
2:43skin, and when that water evaporates, it
2:45carries heat away with it. That's it.
2:48That's the whole system. Dogs pant.
2:50Elephants use their ears as radiators.
2:52Pigs roll in mud because they can barely
2:54sweat at all. Humans have somewhere
2:56between two and four million sweat
2:58glands, and we are genuinely the best
3:00sweaters in the animal kingdom. The
3:02catch is that the system runs on a
3:04consumable. You are cooling yourself by
3:06spending water, and in the Egyptian
3:08summer, you spend it fast.
3:10A laborer working outdoors in that
3:12climate can lose several liters a day.
3:14Lose 2% of your body weight in fluid,
3:16and your cognitive performance drops
3:18measurably. Lose five, and you're in
3:21real trouble. Lose 10, and you're dying,
3:24and you're dying confused because one of
3:26the first things heat takes from you is
3:28your ability to notice that anything's
3:30wrong. There's a second consumable, too,
3:32and this one gets forgotten. Sweat isn't
3:34distilled water. It's salty. Sweat hard
3:38enough, and you can drink all the water
3:39in the world and still crash because you
3:41flushed out the sodium your nervous
3:42system needs to function. That's
3:44hyponatremia, and it will kill you just
3:47as dead as dehydration, with the added
3:49indignity that you'll have a full water
3:51jar in your hand when it happens. So,
3:53the survival equation in ancient Egypt
3:55comes down to three things: reduce heat
3:57load, replace water, replace salt.
4:01Everything that follows is just
4:02increasingly clever versions of those
4:04three moves. Move one, the building is
4:06the air conditioner. Start with the
4:08house because this is where the
4:10Egyptians were quietly brilliant.
4:12Egyptian domestic architecture was mud
4:15brick, Nile silt mixed with chopped
4:17straw packed into molds baked hard in
4:20the very sun it was designed to defeat.
4:23There's a nice irony in that, and mud
4:25brick has a property that modern
4:27building materials have spent decades
4:29trying to get back, enormous thermal
4:32mass. Here's what that means in
4:33practice. A thick mud brick wall doesn't
4:36block heat, it delays it. Sun hits the
4:39wall all day and the heat crawls through
4:41the material slowly, taking hours to
4:43make the journey. So, the peak heat of
4:46the afternoon arrives inside your house
4:48around midnight, by which time the
4:50desert night has gone cold and you
4:52actually want it. Then the cold of the
4:54night crawls through and arrives inside
4:56at midday when you're desperate for it.
4:58The wall isn't insulation, it's a time
5:00machine for temperature. It takes the
5:02daily swing, which in the Egyptian
5:04desert can be 20° C between noon and
5:07dawn, and flips it exactly out of phase
5:09with your needs. Nobody in 1350 BCE was
5:13writing equations about thermal lag.
5:16They just noticed that thick walls made
5:17the house better and thin walls made it
5:19worse, and they built accordingly for
5:213,000 years. Then they stacked more
5:24tricks on top. Windows were small and
5:26set high near the ceiling because hot
5:28air rises and you want the exit near the
5:30top. Walls were whitewashed, which
5:33reflects a substantial portion of
5:34incoming solar radiation rather than
5:36absorbing it. Streets in worker
5:38settlements like Deir el-Medina, the
5:40village that housed the craftsmen who
5:42cut the royal tombs, were narrow, which
5:44meant the buildings shaded each other
5:46for most of the day. Rooms were arranged
5:48so the ones you used in the afternoon
5:50sat on the shaded side. And then there's
5:52the roof. Egyptian roofs were flat and
5:55the flat roof was a functional living
5:57space. You slept up there.
6:00In the hot months a huge portion of the
6:02population simply moved their bed to the
6:04roof at night where the air moved and
6:06heat radiated away into a cloudless sky.
6:09Sleeping on the roof in an Egyptian
6:11summer isn't poverty. It's the premium
6:14suite. Move two, the wind catcher. Now
6:17here's where it gets interesting.
6:18Egyptian houses had a feature called a
6:21malkaf. You'll see them depicted in tomb
6:23paintings. Most famously in the tomb of
6:26Nebamun at Thebes dating to around 1300
6:29BCE which shows a structure on a roof
6:32that is unmistakably a wind scoop. The
6:35malkaf is a hooded vent built on the
6:37roof angled to face the prevailing wind
6:40in Egypt reliably out of the north. Wind
6:43hits the scoop gets funneled down a
6:45shaft and is delivered directly into the
6:47living space below. Meanwhile, hot air
6:50being hot is rising and escaping through
6:52those high windows on the other side.
6:54You've created a pressure difference.
6:56You've built a chimney that runs
6:57sideways. That's passive ventilation. No
7:01moving parts and no power source. It
7:03works because wind exists and heat rises
7:06and both of those things are going to
7:08keep being true forever. And the
7:10Egyptians took it one step further which
7:12is the part that makes me slightly
7:14emotional. Some households would place
7:16porous clay water jars in the path of
7:18that incoming air. Water seeps through
7:20the clay, evaporates off the outer
7:22surface and evaporation takes heat with
7:25it. The air arriving in your room has
7:27now been cooled by passing over an
7:29evaporating surface. That's an
7:31evaporative cooler. That's a swamp
7:33cooler. That is in principle the exact
7:36same machine you can buy today at a
7:38hardware store for $200 running on
7:41electricity and they built it out of a
7:43pot and a hole in the roof. This design
7:46didn't die with Egypt, by the way.
7:48Wind catchers spread and evolved across
7:50the Middle East and Persia into the
7:52towering bad-gears of Yazd in Iran, some
7:55of which still stand and still work.
7:57The technology never actually stopped
7:59being good. We just got access to cheap
8:01electricity and decided we'd rather
8:03solve the problem by burning things.
8:05Move three, linen and why covering up
8:07beats stripping off. Let's talk about
8:09clothes. Your instinct in extreme heat
8:12is to wear as little as possible. The
8:14Egyptian answer was more nuanced than
8:16that, and the nuance is the interesting
8:18part. Egyptian clothing was almost
8:20universally linen, made from flax, and
8:23the reason is a stack of material
8:25properties that happen to line up
8:27perfectly with the problem. Linen is
8:30highly breathable. The fibers are
8:32hollow, so air moves through the weave.
8:34It's exceptionally good at wicking,
8:36meaning it pulls sweat off your skin and
8:38spreads it across a wide surface where
8:40it can evaporate efficiently. And it's a
8:42poor insulator, so it doesn't trap the
8:44heat you're trying to lose. Cotton, for
8:46comparison, holds moisture against the
8:48skin. Wool insulates. Linen does
8:51neither. In that specific climate, it is
8:53close to the ideal fabric, and the
8:55Egyptians figured that out early enough
8:58that flax cultivation became one of the
9:00foundational industries of the entire
9:02civilization. There's also a quality
9:04gradient here that tells you everything
9:06about Egyptian society. The finest
9:08linen, sometimes called royal linen, was
9:11woven so finely that surviving fragments
9:14are nearly transparent. And producing it
9:16took skilled weavers enormous amounts of
9:18time. Elites wore that. Field laborers
9:21wore coarse, thick linen, or a simple
9:24kilt, or in a lot of cases very little
9:26at all. Same climate, same material,
9:30radically different experience of it.
9:32That gap runs through this entire story,
9:34and we'll come come to it. And then the
9:36counter-intuitive bit, loose,
9:38light-colored cloth over your skin can
9:40keep you cooler than bare skin because
9:43it blocks direct solar radiation while
9:45still letting sweat evaporate. You lose
9:47a little airflow, you gain a lot of
9:49shade. It's the same reason desert
9:51peoples across North Africa and Arabia
9:53converged on flowing robes rather than
9:55shorts.
9:56Being naked in the desert sun isn't
9:58freedom, it's just faster sunburn, which
10:01brings us to hair. Egyptians,
10:03particularly the wealthy, frequently
10:05shaved their heads and wore wigs. This
10:07looks purely like fashion, and partly it
10:10was, and partly it was about lice, which
10:12nobody enjoys. But a wig sits slightly
10:15off the scalp, creating a ventilated air
10:17gap, and it can be removed. Your actual
10:20hair cannot.
10:21Shave the head and you've got a surface
10:23you can wash, cool, and cover on demand.
10:26The Egyptians were also famously
10:28obsessive about cleanliness and oils.
10:30Priests bathed multiple times daily.
10:33Ordinary people used scented fats and
10:35oils on the skin, which protected
10:36against sun damage and cracking in
10:38extremely dry air. Herodotus, visiting
10:41centuries later, noted the Egyptian
10:42preoccupation with washing with a slight
10:44tone of bewilderment, which is very
10:46funny coming from a Greek. Move four,
10:49drink beer, seriously. Here's the fluid
10:51problem. You need several liters of
10:53water a day. The Nile is right there.
10:56The Nile is also full of parasites,
10:58silt, animal waste, human waste, and,
11:01depending on the season and how far
11:03upstream the last village was, things
11:05you do not want to think about while
11:07drinking. Schistosomiasis, a parasitic
11:10disease spread through freshwater
11:12snails, has been detected in Egyptian
11:14mummies. Drinking straight from the
11:16river was not free. So, Egyptians drank
11:19beer, vast, structural,
11:21civilization-scale amounts of beer. And
11:24I need to be clear about what this beer
11:25was because it wasn't a pint. Egyptian
11:28beer was thick, low in alcohol, made
11:30from barley or emmer wheat, often
11:32strained but still substantial enough
11:34that some descriptions put it closer to
11:36a gruel than a drink. It was food. It
11:39was hydration. It was calories. It
11:42carried B vitamins from the yeast.
11:44Crucially, the brewing process involved
11:46heating the mash and the fermentation
11:48itself produces an environment that's
11:50hostile to a lot of pathogens. Beer was,
11:53for practical purposes, safer than the
11:55river it came from. How structural was
11:58this? Workers were paid The records from
12:01Deir el-Medina,
12:03one of the best-documented workforces in
12:05the entire ancient world, because these
12:07people wrote down everything on
12:08limestone flakes, including their
12:10absences and their complaints, show
12:12rations of bread and beer as standard
12:14compensation. Daily allowances of
12:16multiple jars per worker appear in the
12:18record. And in one of the great moments
12:20in labor history, when those workers'
12:22rations were delivered late during the
12:24reign of Ramesses III, around 1155 BCE,
12:28they downed tools and staged what is
12:30generally considered the first recorded
12:32strike in human history. They walked off
12:34the royal necropolis over food and beer.
12:37Sitting behind that strike is the thing
12:39we established earlier. In that climate,
12:41the ration wasn't a perk. It was the
12:43cooling system. Cut the beer and you're
12:45not being stingy, you're switching off
12:47the water supply for men doing heavy
12:48labor in a desert. Move five, salt,
12:52bread, and the invisible chemistry. Now
12:54the part nobody thinks about. You've
12:56replaced the water, you have not
12:58replaced the salt, and the salt is what
13:00stops muscles and your brain from going
13:02soft in the afternoon.
13:04The Egyptian diet handled this almost by
13:07accident. Bread was the staple, coarse,
13:10dense, and gritty enough that it visibly
13:12wore down the teeth of the population,
13:14which we can see in surviving mummies as
13:16heavily abraded molars. Salted and dried
13:19fish was a common preserved food.
13:21Natron, the naturally occurring sodium
13:24compound harvested from dried lake beds,
13:27and famous for its role in
13:28mummification, also had domestic uses.
13:31Onions, garlic, dates, figs, dates in
13:35particular being an efficient package of
13:37sugar and potassium. None of this was
13:39designed as an electrolyte strategy.
13:41Nobody was thinking about sodium ions,
13:43but a diet built on salted preserved
13:46fish, salted bread, and potassium-rich
13:49fruit consumed alongside enormous
13:51volumes of low-alcohol beer produces
13:53almost exactly the fluid and mineral
13:55balance that a person doing heavy
13:57outdoor labor in extreme heat requires.
14:00That's the pattern that keeps repeating
14:02in this story, not knowledge, iteration.
14:05A few thousand years of doing the thing
14:07that worked and quietly dropping the
14:08thing that didn't until the accumulated
14:10result looks like it was designed by
14:12someone with a physiology textbook. Move
14:14six, don't be outside. The simplest
14:16solution is the one we skipped. So,
14:18let's do it now. The Egyptian day was
14:21structured around the sun rather than
14:22against it. Work started before dawn.
14:25Heavy labor happened in the cool of
14:27early morning. The middle of the day,
14:29the genuinely dangerous window, was for
14:31rest, shade, food, and sleep. Then work
14:35resumed as the sun dropped. Deir
14:37el-Medina again gives us the detail
14:39because those workers recorded their
14:40schedule. They worked in shifts, they
14:43had rest days, and during the working
14:45period many of them stayed in temporary
14:47huts up near the tombs in the Valley of
14:49the Kings, rather than walking home
14:51across open ground twice a day in the
14:53heat. Even the great construction
14:55projects appear to have run on seasonal
14:57logic. A significant portion of pyramid
14:59building labor is thought to have been
15:00organized around the annual Nile
15:02inundation. When the fields flooded,
15:04agricultural work paused, and a large
15:07labor force became available. And the
15:09flood also made it dramatically easier
15:11to move stone by boat.
15:13The work day, the work year, and the
15:15calendar itself all bent around the sun
15:17and the river. And they had medicine for
15:19when it went wrong anyway.
15:21The Ebers Papyrus, dating to around 1550
15:25BCE, is one of the oldest surviving
15:28medical texts on Earth, and it contains
15:30remedies for fever, for burns, for
15:32headache, for a whole catalog of
15:34conditions consistent with heat
15:36exposure. Some of it is magical
15:38incantation. Some of it, honey on
15:40wounds, which we now know has genuine
15:42antibacterial properties, turns out to
15:44work. That mixture of the empirical and
15:46the mystical, side by side, entirely
15:49unbothered by the contradiction, is very
15:51much the ancient world in general. The
15:53twist, the desert was the point. All
15:56right, here's where this whole story
15:57turns over. We've been treating the
15:59desert as the problem. Everything so far
16:01has been Egyptians defending against it,
16:04but ancient Egypt existed because of the
16:06desert. The Egyptians called the fertile
16:08black soil of the flood plain Kemet, the
16:11black land. They called the desert
16:13Deshret, the red land. Two names, two
16:17worlds, one border you could stand with
16:19a foot on each side of. And the red land
16:22was, functionally, a wall. It's the
16:25reason Egypt held a recognizable
16:27identity for 3,000 years while
16:29civilizations in Mesopotamia were being
16:31conquered and reconquered on what feels
16:33like a rotating schedule. Egypt was
16:35flanked east and west by hundreds of
16:37kilometers of lethal, waterless sand.
16:40Armies can't cross that. Supply lines
16:42can't cross that. The desert was a moat
16:45that no one had to build, maintain, or
16:47garrison. And it went further than
16:49defense. The desert's aridity is the
16:51reason we know anything about Egypt at
16:53all. Organic material, papyrus, linen,
16:57wood, painted plaster, human tissue,
17:00rots in humidity and survives in
17:02dryness. Every papyrus scroll in every
17:05museum, every preserved body, every
17:08scrap of painted cloth, exists because
17:10the climate that made life difficult
17:12made decay nearly impossible.
17:15Mummification itself is a technology
17:17built directly out of local geology.
17:20The Egyptians noticed that bodies buried
17:22in hot dry sand naturally desiccated and
17:25survived, and the entire elaborate
17:27apparatus of embalming was, at bottom,
17:30an attempt to reproduce artificially
17:32what the desert did for free. Natron,
17:34the salt they used to dry the body, came
17:37out of desert lake beds. So, the heat
17:39didn't just get survived. It got
17:41recruited. It defended the borders. It
17:43dried the dead. It preserved the
17:45archive. And it is the single reason a
17:47civilization from 3000 BCE is better
17:51documented than most of medieval Europe.
17:53Here's what I keep coming back to. There
17:55is a house in Egypt 3 and 1/2 thousand
17:58years ago. Thick mud walls holding
18:00yesterday's cool. A scoop on the roof
18:02pulling the north wind down into the
18:04rooms. A porous clay jar sitting in the
18:06airflow. Sweating, taking the heat out
18:09of the breeze. A family asleep on the
18:11roof under a sky with no clouds in it. A
18:14jar of thick beer for the morning. Not
18:17one part of that requires electricity.
18:20Not one part of it will ever break in a
18:21way that can't be fixed with mud and
18:23hands. It has no off switch because it
18:26has no on switch. And it was arrived at,
18:28not by genius, but by several thousand
18:30years of people paying close attention
18:32to what made the afternoon bearable and
18:34passing that on to their kids. We've
18:36spent the last 100 years solving the
18:38same problem by putting a machine in the
18:40window and cooling one room at a time.
18:42While the machine dumps its waste heat
18:44into the street and makes the city
18:45hotter, so we buy a bigger machine.
18:48Meanwhile, architects are now going back
18:50to the tomb paintings at Thebes and
18:51studying the Malkata because it turns
18:54out a hole in the roof pointed at the
18:55wind was a genuinely excellent idea and
18:58always has been. You will get warm
19:00today, and you'll do something about it.
19:02Move to shade, drink something cold, sit
19:05near a fan, change what you're wearing,
19:07wait for the sun to drop. Small
19:10automatic adjustments you won't even
19:11register making. That's the same
19:13equipment, same species, same sweat
19:16glands, same 2% margin before the
19:19thinking starts going. The Egyptian in
19:21Thebes at noon in 1350 BCE was running
19:25the same calculation you run, with
19:27better architecture and worse beer.
19:293,000 years of the hottest place people
19:31chose to live, and the answer was never
19:34toughness. It was mud, linen, shade,
19:37salt, and paying attention. So, could
19:41you do it? A summer in ancient Thebes,
19:43no fridge, no fan, roof for a bedroom,
19:47and a jar of warm beer for breakfast.
19:49Let me know in the comments. Until then,
19:52see you soon.