Memories are shaky things. Maybe you remember a family trip to the beach or learning to swim as a child. But could you name the exact date, or even the year, these events happened? Without the help of a daily diary, it’s nothing more than guesswork.
The same problem applies to cultural memories and history. And the further back in time you go, the more difficult it is to know when (or if) something actually happened.
The Iron Age Levant, which occurred 1200-500 B.C., is one example of a historical period of particularly murky chronology. It’s a time when many of the cultural histories of the Near East, North Africa and Europe were created, passed on through stories originally from the Hebrew Bible.
Matching events in the holy texts with actual history is a contentious issue among researchers.
"It’s called the Iron Age chronology debate. It’s a huge argument about the chronology of events in the bible," Yoav Vaknin, an archeologist at Tel Aviv University and Hebrew University of Jerusalem, told DW.
Vaknin recently published a paper with colleagues that utilizes a new method called "geomagnetic dating" to piece together when certain events during the Iron Age Levant took place.
How history is pieced together
Historians and archeologists use two main sources of information to find out when, where, and if historical events happened.
"We know a lot about the chronology of ancient Levant from the Hebrew bible [as well as] Assyrian and Egyptian texts," said Helen Gries, a curator at the Pergamon museum in Berlin.
However, texts are often written and adapted decades or hundreds of years after an event took place, making it difficult to verify their authenticity.
Some texts, like the Triumphal Relief at Karnak Temple in Egypt, which depicts Pharaoh Shoshenq I conquering Judean lands around 900 B.C., might be little more than the vain boasts of a megalomaniacal king, for example.
Researchers can also date events by examining pottery remnants from archeological sites, which have layers of debris and artifacts — the deeper you go, the further back in history you are.
"But the problem is that this is relative chronology. We know what comes early and later, but it doesn’t tell us when things happened," Gries told DW.
Dating events with magnetism and fire
In Vaknin’s study, published in PNAS last week, authors described a new scientific trick to help date events — specifically ones involving fire.
The researchers facilitated a process called archaeomagnetic dating, a method using magnetism that they say offers more precise ways to date artifacts.
To explain how archaeomagnetic dating works, it’s first important to know that the Earth’s magnetic field changes over time. Second, when they are heated to hundreds of degrees Celsius, microscopic magnetic compounds in materials like clay align themselves with the Earth’s changing magnetic field.
"Cities at that time were built with sun-dried mud bricks. When they are heated up, like in a destructive fire, the ferromagnetic minerals inside the bricks align with a magnetic field like compass needles. When it cools, they become stuck – a time lock of when the fire took place," Vaknin explained.
By examining these "time locks", the researchers were able to better pinpoint when certain historical events happened.
Pharaoh Shoshenq may not have been bluffing after all
Originally, historians doubted whether Pharaoh Shoshenq I actually conquered the Levant with force around 900 B.C.
"Most historians think Shoshenq didn’t destroy anything when he invaded the Levant — instead they think Judean cities paid him to go away so he wouldn’t destroy anything," Vaknin said.
However, with the aid of the new archaeomagnetic dating method, Vaknin said the Pharaoh may have been telling the truth about his destructive tendencies after all.
Vaknin studied evidence of destruction in the Judean city Tel Beth-Shean. Excavators of the site originally suggested the city was destroyed sometime around 830 B.C. In the bible, this matches with a military campaign into the Kingdom of Judah led by Hazael, King of Aram Damascus.
Vaknin took samples of bricks from Tel Beth-Shean that were burned in some sort of fire. The geomagnetic data he was able to excavate from the samples suggests the city was actually destroyed eighty years earlier, around 900 B.C.
"This ruled out destruction by King Hazael. Instead, the timing of the fire does correspond with Shoshenq’s campaign," Vaknin said.
Vaknin and his co-authors say their work doesn’t prove that Shoshenq definitely destroyed Beth-Shean. Rather, they say, it provides an example of how archaeomagnetic dating can help improve understanding of when historical events took place and contribute to ongoing debates about the chronology of the rulers of Israel and Judah.
Another piece of the historical puzzle
Although geomagnetic data can be helpful in telling us when destruction happens, Dieter Vieweger, director of the German Protestant Institute for Archeology, said the method also has its weaknesses.
"The problem is with interpretation. Yes, we date the fire and destruction of the city, but the data doesn’t tell us if it was caused by warfare or fire calamity from an earthquake," Vieweger said.
In order to understand specific causes of destruction, historians and archeologists still have to supplement the knowledge acquired through archaeomagnetic dating with historical texts and archeological findings.
Vieweger said that geomagnetic data won’t solve the problem with dating, but does help provide one more piece in the historical puzzle.
"The next project is [to figure out] what happened a few hundred years earlier. Here the debates are much bigger," Vaknin said, referring to the time when Ancient Israelites settled the land of Canaan.
According to Gries, this is the point of archeology and history.
"We cannot say with absolute certainty what happened in the past, but [we can] reconstruct what is most likely to have happened," she said.
Edited by: Clare Roth