How DNA has been preserved in archaeological deposits for thousands of years

For a long time, most archaeologists believed that buried archaeological deposits were a by-product of excavation work and were insignificant
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However, in recent years, it has been discovered that sediments may contain ancient biological molecules, including DNA

To investigate the origin of DNA in sediments, Max Planck’s researchers collaborated with an international team of geoarchaeologists—archaeologists use geological techniques to reconstruct the formation of sediments and sites—to study sediments on a microscopic scale.
The preservation of DNA in China
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They used undisturbed sediment blocks previously removed from the archaeological site and soaked in similar synthetic plastic (polyester) resin

The researchers successfully extracted DNA from a set of sediments in Africa, Asia, Europe and North America, which were prepared 40 years ago
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"These DNA blocks are an excellent source of ancient DNA (including DNA from ancient humans), although plastics are often stored for decades.

Rich in trace residues in sediment matrix

The scientists used sediment blocks from Denisova Cave, located in the Altai Mountains in south-central Siberia, where Neanderthals and Denisovans were extracted And the ancient DNA of modern people, and showed that small organic particles produced more DNA than randomly sampled sediments
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"This clearly shows that the high success rate of extracting ancient mammalian DNA from Denisovan cave sediments comes from the abundance of micro-remains in the sediment matrix, and not from feces, body fluids, or decomposition that may be adsorbed on mineral particles.

The method described in the study allows highly localized micro-scale sampling of sediments for DNA analysis and shows that ancient DNA (aDNA) is not evenly distributed in sediments; specific sediment features are more conducive to preservation than others Ancient DNA

The lead author of the study, Diyendo Massilani, recovered a large amount of Neanderthal DNA from just a few milligrams of sediment
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He can determine the gender of the individuals who left the DNA and show that they belong to a population related to Neanderthals whose genome was previously reconstructed from a bone fragment found in a cave

Article title

Microstratigraphic preservation of ancient faunal and hominin DNA in Pleistocene cave sediments