It’s always interesting when two intriguing academic disciplines intersect. Archeoastronomy is the best example, where scientists study historical remains and determine how ancient peoples saw and used the sky. If you like looking at the ground and looking at the sky, archeoastronomy provides a way to study and enjoy the best of both.
So much of our modern life, how we view the sky, how we keep time, how we calculate everything, is governed by the innovations of early people, particularly Mesopotamians. Perhaps we don’t even realize the legacy of their impact. Put that together with their supernatural beliefs, oftentimes attributing their knowledge to the work of imparting supernatural entities – or ‘gods’ who guided their culture and became their heroes and our modern world just gets much more interesting.
But how do we tell how old some of the stuff we find in the ground is? Traditionally stratification was the key. The further down something was in the ground, the older it was presumed to be. After that came carbon 14 dating which provided a scientific method to determine the age of artifacts containing carbon. And now, thanks to archeomagnetics, the combination of archaeology and the study of the earth’s electromagnetic field, there is another way to date historical artifacts.
“Baked bricks provide an ideal target for archaeomagnetic sampling,” according to a new study in the Proceedings of the National Academy of Science. “Since many such bricks feature stamped or inscribed inscriptions in Sumerian or Akkadian, enabling these artifacts to be precisely dated to the reigns of individual Mesopotamian kings whose names often adorn the bricks.”
This study, published in the December 18 issue of PNAS did not pioneer this novel approach of determining the strength of the earth’s magnetic field by analyzing its impact on grains of iron within artifacts under study. The technique has been used before on ceramic and hearth material producing limited, but useful datasets.
Previous studies showed that the Levant, which is better studied and has better data, had experienced a spike in geomagnetic activity between approximately 1050 and 550 BC. This epoch, known as the Levantine Iron Age geomagnetic Anomaly (LIAA), has been corroborated in other locations but, interestingly, hadn’t been observed in previous work from nearby Mesopotamia.
The authors of this study started with an assemblage of 139 fired and inscribed clay objects. 120 bricks came from the Slemani Museum in Iraqi Kurdistan, 16 baked bricks and two clay cones came from the Yale Babylonian Collection, and one baked brick was recently excavation by the al-Qadisiyah University at a site in Marad.
“Of the 139 objects, 40 were chosen for initial archaeomagnetic study based on characteristics including legibility of inscription and range of chronology,” the study says.
38 of the 40 bricks have inscriptions that allow them to be dated to the reign of kings like Nebuchadnezzar II, Shulgi and Nabonidus and the previously unknown king Iakūn-dīri of Hurshitum. These bricks range from the 3rd to the 1st Millenia BC and provide a good base of reference for this study.
The researchers were able to use baked bricks in their geomagnetic analysis which produced a high-quality reference for dating other objects. They were also able to observe the Levantine Iron Age geomagnetic Anomaly which had previously been absent in the available data.
“Our data help contribute to increasing the resolution of the curve during these key periods for the Levantine Archaeomagnetic Curve in general as well as contributing to the archaeointensity curve for Mesopotamia specifically,” the study says.
The abstract for the study is available on the PNAS website (https://www.pnas.org/doi/10.1073/pnas.2313361120) but the remainder of the study is behind their paywall. However, the datasets from the study are available for download from the PNAS site and there is a link to a github repository of images of the bricks used in the study.
A PDF of the entire study can be found (for free) at the following URL: