Near the river Tigris, outside the ancient city of Kalhu, known today as Nimrud, northern Iraq, a brickmaker once prepared a clay brick for the construction of a new palace dedicated to his king Ashurnasirpal II (approximately 883-859 BCE). Little did he know, that almost 2,900 years later, this clay brick would serve as a unique time capsule revealing details of the flora from this area and time, through the modern-day investigation of the ancient DNA hidden and preserved for thousands of years. In a new study, researchers from the University of Copenhagen, the University of Oxford and Aalborg University were able to extract ancient DNA from a recently exposed fracture surface of the 2,900-year-old clay brick and detect 34 unique taxonomic groups of plants.
During a digitalization project at the National Museum of Denmark in 2020, Dr. Sophie Lund Rasmussen and her colleagues obtained samples from the inner core of the 2,900-year-old clay brick — meaning that there was a low risk of DNA contamination since the brick was created.
The researchers extracted DNA from the samples by adapting a protocol previously used for other porous materials, such as bone.
After the extracted DNA had been sequenced, they identified 34 distinct taxonomic groups of plants.
The plant families with the most abundant sequences were Brassicaceae (cabbage) and Ericaceae (heather).
Other represented families were Betulaceae (birch), Lauraceae (laurels), Selineae (umbellifiers) and Triticeae (cultivated grasses).
With the interdisciplinary team comprising assyriologists, archaeologists, biologists, and geneticists, they were able to compare their findings with modern-day botanical records from Iraq as well as ancient Assyrian plant descriptions.
The brick would have been made primarily of mud collected near the local Tigris river, mixed with material such as chaff or straw, or animal dung.
It would have been shaped in a mould before being inscribed with cuneiform script, then left in…
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