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Death and taxes are famously inevitable,
but what about decomposition?

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As anyone who's seen a mummy knows,

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ancient Egyptians went to a lot of trouble
to evade decomposition.

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So, how successful were they?

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Living cells constantly renew themselves.

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Specialized enzymes 
decompose old structures,

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and the raw materials 
are used to build new ones.

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But what happens when someone dies?

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Their dead cells are no longer
able to renew themselves,

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but the enzymes 
keep breaking everything down.

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So anyone looking to preserve a body

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needed to get ahead of those enzymes
before the tissues began to rot.

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Neurons die quickly,

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so brains were a lost cause
to Ancient Egyptian mummifiers,

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which is why, according 
to Greek historian Herodotus,

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they started the process
by hammering a spike into the skull,

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mashing up the brain, 
flushing it out the nose

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and pouring tree resins into the skull
to prevent further decomposition.

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Brains may decay first,
but decaying guts are much worse.

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The liver, stomach and intestines
contain digestive enzymes and bacteria,

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which, upon death, start eating
the corpse from the inside.

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So the priests removed the lungs
and abdominal organs first.

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It was difficult to remove the lungs
without damaging the heart,

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but because the heart was believed
to be the seat of the soul,

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they treated it with special care.

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They placed the visceral organs in jars

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filled with a naturally occurring salt
called natron.

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Like any salt, natron can prevent decay 
by killing bacteria

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and preventing the body's natural
digestive enzymes from working.

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But natron isn't just any salt.

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It's mainly a mixture 
of two alkaline salts,

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soda ash and baking soda.

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Alkaline salts are especially
deadly to bacteria.

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And they can turn fatty membranes
into a hard, soapy substance,

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thereby maintaining 
the corpse's structure.

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After dealing with the internal organs,

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the priest stuffed the body cavity
with sacks of more natron

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and washed it clean to disinfect the skin.

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Then, the corpse was set in a bed
of still more natron

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for about 35 days 
to preserve its outer flesh.

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By the time of its removal,

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the alkaline salts 
had sucked the fluid from the body

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and formed hard brown clumps.

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The corpse wasn't putrid,

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but it didn't exactly smell good, either.

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So, priests poured tree resin over
the body to seal it,

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massaged it with a waxy mixture
that included cedar oil,

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and then wrapped it in linen.

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Finally, they placed the mummy
in a series of nested coffins

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and sometimes even a stone sarcophagus.

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So how successful were 
the ancient Egyptians at evading decay?

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On one hand, mummies are definitely not
intact human bodies.

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Their brains have been mashed up
and flushed out,

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their organs have been removed
and salted like salami,

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and about half of their remaining
body mass has been drained away.

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Still, what remains 
is amazingly well-preserved.

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Even after thousands of years,

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scientists can perform autopsies 
on mummies

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to determine their causes of death,

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and possibly even isolate DNA samples.

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This has given us new information.

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For example, it seems that air pollution
was a serious problem in ancient Egypt,

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probably because of indoor fires 
used to bake bread.

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Cardiovascular disease was also common,
as was tuberculosis.

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So ancient Egyptians were somewhat
successful at evading decay.

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Still, like death, taxes are inevitable.

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When some mummies were transported,
they were taxed as salted fish.