0:00:06.794,0:00:08.455
Since the dawn of humanity,

0:00:08.455,0:00:13.876
an estimated 100.8 billion[br]people have lived and died,

0:00:13.876,0:00:19.236
a number that increases by about[br].8% of the world's population each year.

0:00:19.236,0:00:22.456
What happens to all [br]of those people's bodies after they die

0:00:22.456,0:00:26.715
and will the planet eventually[br]run out of burial space?

0:00:26.715,0:00:28.506
When a person's heart stops beating,

0:00:28.506,0:00:32.656
the body passes through several[br]stages before it begins decomposing.

0:00:32.656,0:00:34.287
Within minutes after death,

0:00:34.287,0:00:37.966
the blood begins settling in[br]the lower-most parts of the body.

0:00:37.966,0:00:40.005
Usually eight to twelve hours later,

0:00:40.005,0:00:46.084
the skin in those areas is discolored[br]by livor mortis, or post-mortem stain.

0:00:46.084,0:00:49.896
And while at the moment of death[br]the body's muscles relax completely

0:00:49.896,0:00:52.677
in a condition called primary flaccidity,

0:00:52.677,0:00:58.247
they stiffen about two to six hours later[br]in what's known as rigor mortis.

0:00:58.247,0:01:00.377
This stiffening spreads [br]through the muscles,

0:01:00.377,0:01:05.587
and its speed can be affected by age,[br]gender, and the surrounding environment.

0:01:05.587,0:01:07.588
The body also changes temperature,

0:01:07.588,0:01:10.897
usually cooling off [br]to match its environment.

0:01:10.897,0:01:13.055
Next comes decomposition,

0:01:13.055,0:01:17.238
the process by which bacteria and insects[br]break apart the body.

0:01:17.238,0:01:20.277
Many factors affect [br]the rate of decomposition.

0:01:20.277,0:01:24.797
There is, however, a basic guide of the[br]effect of the environment on decompositon

0:01:24.797,0:01:26.758
called Casper's Law.

0:01:26.758,0:01:28.967
It says that if all other [br]factors are equal,

0:01:28.967,0:01:35.198
a body exposed to air decomposes twice[br]as fast as one immersed in water

0:01:35.198,0:01:39.322
and eight times as fast [br]as one buried in earth.

0:01:39.322,0:01:43.554
Soil acidity also greatly [br]affects bone preservation.

0:01:43.554,0:01:46.981
High-acidity soils with [br]a pH of less than 5.3

0:01:46.981,0:01:49.658
will rapidly decompose bone,

0:01:49.658,0:01:54.739
whereas in a neutral or basic soil[br]with a pH of 7 or more,

0:01:54.739,0:01:59.685
a skeleton can remain in relatively[br]good condition for centuries.

0:01:59.685,0:02:04.088
Different cultures throughout history have[br]developed unique approaches to burials.

0:02:04.088,0:02:06.720
As far back as [br]the first Neanderthal burials,

0:02:06.720,0:02:09.100
death was accompanied by rituals,

0:02:09.100,0:02:13.418
like the positioning, coloring,[br]or decorating of corpses.

0:02:13.418,0:02:17.002
Traditional Christian burials decorate[br]the body in dress,

0:02:17.002,0:02:18.460
while in traditional Islam,

0:02:18.460,0:02:20.940
a body is wrapped in a piece [br]of ritual fabric

0:02:20.940,0:02:24.059
with the face oriented toward Mecca.

0:02:24.059,0:02:27.023
Traditional Hindus ceremonially burn[br]the body,

0:02:27.023,0:02:31.270
and Zoroastrians, followers of one of the[br]oldest monotheistic religions,

0:02:31.270,0:02:35.643
traditionally place bodies atop a tower[br]to expose them to the Sun

0:02:35.643,0:02:38.004
and scavenging birds.`

0:02:38.004,0:02:42.247
Before the Industrial Revolution,[br]burials were simple and accessible.

0:02:42.247,0:02:47.191
These days, with suitable burial land[br]running out in high-population areas,

0:02:47.191,0:02:50.290
purchasing private gravesites[br]can be costly,

0:02:50.290,0:02:53.047
and many people can't afford[br]simple burials.

0:02:53.047,0:02:56.862
Even cremation, the second most common[br]burial practice in the world,

0:02:56.862,0:02:59.209
comes with a high cost.

0:02:59.209,0:03:01.392
As for the question [br]of running out of space,

0:03:01.392,0:03:04.302
the issue isn't so much about total land[br]in the world

0:03:04.302,0:03:08.788
as it is that large populations cluster[br]together within cities.

0:03:08.788,0:03:10.977
Most of the big cities in the world

0:03:10.977,0:03:14.570
may run out of suitable burial grounds[br]within a century.

0:03:14.570,0:03:16.390
For London, it's even sooner.

0:03:16.390,0:03:18.883
That may happen by 2035.

0:03:18.883,0:03:21.842
So are there alternatives[br]to traditional burials

0:03:21.842,0:03:24.392
that might help with the space issue?

0:03:24.392,0:03:29.341
In some countries, skyscraper cemeteries[br]enable vertical burials.

0:03:29.341,0:03:32.853
Some options focus on the body's[br]relationship with the environment.

0:03:32.853,0:03:37.793
Promession, for example, freeze-dries[br]and pulverizes the body,

0:03:37.793,0:03:40.342
creating a powder [br]that can turn into compost

0:03:40.342,0:03:43.311
when mixed with oxygen and water.

0:03:43.311,0:03:46.458
There are also green burials that use[br]special materials,

0:03:46.458,0:03:48.651
such as biodegradable caskets,

0:03:48.651,0:03:50.542
urns that sprout trees,

0:03:50.542,0:03:53.802
and burial suits that grow mushrooms.

0:03:53.802,0:03:57.442
Eternal reefs take that concept[br]to the depths of the ocean

0:03:57.442,0:04:03.433
using a mixture of ashes and cement[br]to create marine habitats for sea life.

0:04:03.433,0:04:06.552
Death is an inevitable part[br]of the human condition,

0:04:06.552,0:04:10.483
but how we treat bodies and burials[br]continues to evolve.

0:04:10.483,0:04:12.392
We may each have different spiritual,

0:04:12.392,0:04:13.373
religious,

0:04:13.373,0:04:15.943
or practical approaches to dying,

0:04:15.943,0:04:18.533
but the ever-increasing demand[br]for burial space

0:04:18.533,0:04:20.692
might give us a push to be creative

0:04:20.692,0:04:24.663
about where our bodies go[br]after the final stages of life.