Why didn’t this 2,000 year old body decompose? - Carolyn Marshall

1,777,691 views ・ 2021-02-04

TED-Ed


Please double-click on the English subtitles below to play the video.

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In 1984, two field workers discovered a body in a bog outside Cheshire, England.
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Officials named the body the Lindow Man
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and determined that he’d suffered serious injuries,
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including blunt trauma and strangulation.
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But the most shocking thing about this gruesome story
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was that they were able to determine these details from a body over 2,000 years old.
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Typically, decomposition would make such injuries hard to detect
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on a body buried just weeks earlier.
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So why was this corpse so perfectly preserved?
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And why don't all bodies stay in this condition?
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The answers to these questions live six feet underground.
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It may not appear very lively down here,
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but a single teaspoon of soil contains more organisms
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than there are human beings on the planet.
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From bacteria and algae to fungi and protozoa,
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soils are home to one quarter of Earth’s biodiversity.
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And perhaps the soil’s most important inhabitants are microbes,
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organisms no larger than several hundred nanometers
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that decompose all the planet’s dead and dying organic material.
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Imagine we drop an apple in the forest.
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As soon as it contacts the soil,
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worms and other invertebrates begin breaking it down into smaller parts;
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absorbing nutrients from what they consume and excreting the rest.
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This first stage of decomposition sets the scene for microbes.
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The specific microbes present depend on the environment.
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For example, in grasslands and farm fields there tend to be more bacteria,
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which excel at breaking down grass and leaves.
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But in this temperate forest there are more fungi,
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capable of breaking down complex woody materials.
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Looking to harvest more food from the apple’s remains,
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these microbes release enzymes
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that trigger a chemical reaction called oxidation.
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This breaks down the molecules of organic matter, releasing energy,
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carbon, and other nutrients in a process called mineralization.
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Then microbes consume the carbon and some nutrients,
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while excess molecules of nitrogen, sulfur, calcium, and more
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are left behind in the soil.
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As insects and worms eat more of the apple,
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they expose more surface area for these microbial enzymes
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to oxidize and mineralize.
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Even the excretions they leave behind are mined by microbes.
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This continues until the apple is reduced to nothing—
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a process that would take one to two months in a temperate forest.
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Environments that are hot and wet support more microbes
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than places that are cold and dry,
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allowing them to decompose things more quickly.
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And less complex organic materials break down faster.
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But given enough time,
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all organic matter is reduced to microscopic mineral nutrients.
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The atomic bonds between these molecules are too strong to break down any further.
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So instead, these nutrients feed plant life,
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which grow more food that will eventually decompose.
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This constant cycle of creating and decomposing supports all life on Earth.
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But there are a few environments too hostile for these multi-talented microbes—
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including the peat bogs outside Cheshire, England.
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Peat bogs are mostly made of highly acidic Sphagnum mosses.
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These plants acidify the soil while also releasing a compound
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that binds to nitrogen, depriving the area of nutrients.
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Alongside cold northern European temperatures,
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these conditions make it impossible for most microbes to function.
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With nothing to break them down,
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the dead mosses pile up, preventing oxygen from entering the bog.
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The result is a naturally sealed system.
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Whatever organic matter enters a peat bog just sits there— like the Lindow Man.
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The acid of the bog was strong enough
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to dissolve relatively simple material like bone,
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and it turned more complex tissue like skin and organs pitch black.
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But his corpse is otherwise so well-preserved,
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that we can determine he was healthy, mid-20s,
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and potentially wealthy as his body shows few signs of hard labor.
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We even know the Lindow Man’s last meal—
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a still undigested piece of charred bread.
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Scholars are less certain about the circumstances of his death.
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While cold-blooded murder is a possibility,
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the extremity of his injuries suggest a ritual sacrifice.
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Even 2,000 years ago,
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there’s evidence the bog was known for its almost supernatural qualities;
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a place where the soil beneath your feet wasn’t quite dead or alive.
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