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How is Ancient DNA Preserved?

When an organism dies its DNA is rapidly broken down into smaller and smaller fragments through the action of enzymes, oxygen and water. Sometimes this process is slowed enabling small fragments of DNA to survive within the preserved remains of the organism.

Ancient kangaroo jawbone
magnifyFossil kangaroo jawbone

Ancient DNA many thousands of years old can only be found in the remains of organisms preserved under extraordinary conditions. Plants and animals buried in volcanic ash, trapped in amber, frozen deep in the polar ice, or preserved in arid environments may retain fragments of ancient DNA because these environments lack oxygen and water.

Ancient DNA also survives longer when combined with other substances. Hydroxyapatite (a calcium-containing compound found in bones and teeth), some proteins and sugars can all prolong the life of ancient DNA.

For these reasons, the vast majority of fossilised plant and animal material will not contain ancient DNA.

Impression fossils and replacement fossils, in which the biological material has been replaced by minerals, do not contain ancient DNA.

More information about how fossils are formed:

Sand dune
magnifyArid environments can preserve DNA

Ice field
magnifyPolar environments can preserve DNA

Fish from the Koonwarra fossil beds
magnifyImpression fossils do not contain ancient DNA

Partial dinosaur skeleton from Dinosaur Cove
magnifyReplacement fossils do not contain ancient DNA
© Museum Victoria Australia