Cosmic Rays, Tree Rings, and the Real Story of the Building of Jerusalem

A new archaeological study of ancient Jerusalem is forcing experts to reevaluate some of their past assumptions about the history of that holy city. New research has presented evidence that Biblical accounts of that history are more accurate than previously believed, and that Jerusalem was already a growing city even before the reign of the legendary King David, who ruled the United Kingdom of Israel in the early 10th century BC.

In a report just published in the journal PNAS, a team of archaeologists and researchers from the University of Tel Aviv, the Israel Antiquities Authority and the Weizmann Institute of Science explain the exciting and revolutionary results of their detailed study, which emerged from the application of newly refined radiocarbon dating technology. With the most accurate dating results ever obtained from the old city of Jerusalem, the archaeologists claim to have shown infrastructure projects there were initiated centuries earlier than other research had suggested.

“Until now, most researchers have linked Jerusalem's growth to the west, to the period of King Hezekiah – just over 2,700 years ago,” said study co-author Yuval Gadot, an archaeologist from Tel Aviv University, in an interview quoted in the Daily Mail Online.

“The conventional assumption to date has been that the city expanded due to the arrival of refugees from the Kingdom of Israel in the north, following the Assyrian exile. However, the new findings strengthen the view that Jerusalem grew in size and spread towards Mount Zion already in the ninth century BC. This was during the reign of King Jehoash – a hundred years before the Assyrian exile.”

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Just as significantly, the radiocarbon results revealed that Jerusalem actually underwent a growth spurt that predated its more ambitious ninth century expansion. This happened even before the legendary King David ascended to the throne of the United Kingdom of Israel at the dawn of the 10th century.

This united kingdom split up into separate kingdoms in 931 BC, with a less expansive Kingdom of Israel having sovereignty in the north and the Kingdom of Judah (with Jerusalem as its capital) preserving hegemony in the south. It has always been thought that Jerusalem’s expansion was linked to its status as the capital of Judah, but it now appears that this was not the case.

“During the 10th century BC, the days of David and Solomon, this research has shown that the city is occupied in different areas, and seems to have been larger than we thought previously,” explained study co-author Joe Uziel from the Israel Antiquities Authority. 'We can pinpoint specific buildings and relate them to specific kings mentioned in the Biblical text.”

If Jerusalem’s status as a thriving population hub extends back into the late second millennium BC, that might explain why it was chosen to be the capital of Judah in the first place.

Dr Joe Uziel of the Israel Antiquities Authority (left) and Professor Yuval Gadot of Tel Aviv University with a bat skull at the wall in the City of David. (IAA)

Finding the Real Story of the Building of Jerusalem

The radiocarbon dating tests that led to these new and exciting discoveries were performed on organic samples recovered during archaeological excavations of ancient sediment layers associated with different periods of Jerusalem’s construction and expansion. Researchers used the well-preserved remains of grape seeds, date pits and bat skeletons, which were found in conjunction with archaeological ruins and artifacts from Jerusalem’s past, to calculate when exactly specific building projects were launched and completed. 

Remains left in the wall, such as this bat skull, were radiocarbon dated to provide dating. (IAA)

The results of this analysis show that Jerusalem experienced a significant period of urban expansion about 2,900 years ago, firmly contradicting the currently accepted estimates.  The findings also illuminated construction activity in earlier periods of the city’s history, creating the most detailed and accurate timeline of Jerusalem’s urbanization patterns ever produced.

Previous radiocarbon dating efforts in Jerusalem had not produced such useful results. This is because of ancient fluctuations in carbon isotope levels in the first millennium BC, caused by cosmic rays that bombarded earth’s upper atmosphere in elevated quantities from the eighth through the fifth centuries BC. This phenomenon distorted carbon-14 dating results in that time period and in adjacent centuries, making them far less precise and exact than they normally would be.

Fortunately, researchers connected with the Weizmann Institute of Science in Israel eventually discovered a method for correcting carbon dating results obtained from first millennium BC organic samples. This involved making comparisons to dates obtained from the measurement of ancient tree rings, which were not impacted by cosmic rays and therefore produced reliable results, and adjusting the radiocarbon dating data accordingly, to eliminate distortions.

“The resolution of c-14 [radiocarbon dating] was very bad – 200-300 years; it was impossible to distinguish anything else,” explained Weizmann Institute scientist (and study co-author) Elizabetta Boaretto, commenting on the past state of affairs. “With the work we've done in the City of David, we succeeded to reach a resolution less than 10 years, which is really something very, very new and dramatic.”

The stretch of wall, at the eastern slopes of the City of David. (IAA)

The Bible  is a History Book, Science Says

One focus of the new research was an ancient stone wall found in the original center of Jerusalem, which has long been believed to have been constructed by Hezekiah around 700 BC. But the radiocarbon dating results show it was really built during the time when Hezekiah’s great-grandfather, Uzziah, was the king of Judah.

“Until now, many researchers assumed that the wall was built by Hezekiah during his rebellion against Sennacherib, King of Assyria, in order to defend Jerusalem during the Assyrian siege,” Israel Antiquities Authority archaeologist Joe Uziel said. “It is now apparent that the wall in its eastern part, in the area of the City of David, was built earlier, shortly after the great earthquake of Jerusalem, and as part of the [re]construction of the city.”

Notably, this is just how it is described in the Old Testament, in the Second Book of Chronicles. 

 “Uzziah built towers in Jerusalem at the Corner Gate, at the Valley Gate and at the angle of the wall, and he fortified them,” the relevant passage reads, putting the wall construction project in a larger context. Another reference that relates to these events can be found in the Old Testament Book of Amos, that dates its own writing to “two years before the earthquake, when Uzziah was king of Judah.”

It is fascinating that improvements in scientific techniques applied to archaeological and historical study have produced results that coincide so neatly with reports found in the Bible. This would seem to verify the Bible’s usefulness and relevance as a historical text, at least with respect to its stories about the cultural, political and economic development of ancient Jerusalem.

Top image: Reproduction of the Old city of Jerusalem. Source: Alessandro/Adobe Stock

By Nathan Falde