DNA “time capsule” extracted from 2,900-year-old brick

Time capsules are a fun way to get a glimpse into everyday life in the past, and now scientists have opened one from almost 3,000 years ago. The team successfully extracted DNA from inside an ancient clay brick, revealing a variety of plants from the area at the time.

According to an engraved inscription, the brick originally came from the ancient city of Kalhu in what is now northern Iraq, where it was part of the palace of Ashurnasirpal II, a king of Assyria during the 9th century BCE. Because archeologists know fairly precisely when construction on that palace started, they can date the brick to within a specific decade – between 879 and 869 BCE.

Now housed in the National Museum of Denmark, scientists suspected there could be DNA preserved inside the brick from the time of its production. It’s believed it would have been made mostly of mud collected from the nearby Tigris river, and mixed with chaff, straw, animal dung or other waste materials on hand. It then would have been molded into shape, inscribed and finally left out to dry naturally. This process, the team says, should have preserved any DNA inside better than bricks fired in high heat.

To find out, the researchers drilled samples from the inner core of the brick, through a newly exposed surface after part of the brick split during handling in 2020. Doing it this way ensured that the samples were free from modern contamination. The team then used a DNA extraction technique often used on materials like bone, and sequenced the genetic material they found.

In the end, they identified the DNA of 34 different groups of plants within the samples. Cabbage and heather were the most common ones, while others included birch, laurels, umbellifers and cultivated grasses.

“We were absolutely thrilled to discover that ancient DNA, effectively protected from contamination inside a mass of clay, can successfully be extracted from a 2,900-year-old brick,” said Dr. Sophie Lund Rasmussen, co-first author of the study.

The team says that the technique could be applied to other clay construction materials and ceramic artefacts from essentially any archeological site around the world. And while this study only found viable DNA from plants, it should work with animals, invertebrates, and indeed any living thing, building out a picture of what kinds of life existed around that area at the time.

“Because of the inscription on the brick, we can allocate the clay to a relatively specific period of time in a particular region, which means the brick serves as a biodiversity time-capsule of information regarding a single site and its surroundings,” said Dr Troels Arbøll, co-first author of the study. “In this case, it provides researchers with a unique access to the ancient Assyrians.”

The research was published in the journal Nature Scientific Reports.

Source: Oxford University

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