If trees could speak - How archaeologists use tree rings to uncover history's secrets

Trees may hold the key to uncovering the secrets of ancient civilisations. Scientists have discovered a new way to look at tree-rings, which they believe could help them to accurately date events from the distant past.

To plot the history of Western civilisation before 763 BCE, archaeologists only have access to sparse evidence. Most of the time, they rely on standard radiocarbon measurements to provide the best estimates of specific historical events – the problem is that these can be inaccurate by as much as 200 to 300 years.

In a paper published in Proceedings of the Royal Society A, scientists from the University of Oxford have proceeded to design a new dating method, which they say could help them to anchor exactly when particular events happened.

With a more precise chronology of the past, they hope to gain a better insight of ancient cultures, like the Egyptians and the Mayas.

Solar activity and tree rings

The scientists have begun their research by looking at tree rings that grew in the years 775 and 994 CE. These rings bear the traces of spikes in atmospheric radiocarbon activity caused by a solar storms that occurred during this period. These storms are major solar energetic particle events that result in the Earth being hit by intense bursts of radiation.

Based on these observations, the scientists explain it would be possible to detect similar spikes elsewhere within the thousands of years of available tree-ring material from across the world. Only a few of these markers would be necessary to piece together a reliable dating framework for important civilisations.

The interesting thing about this method is that these radiocarbon time-markers will have affected every living plant or tree that grew at the time of a radiation surge, including in the timber used in ancient buildings. This means that analysing these artefacts from ancient civilisations - looking for signs of radiocarbon surge and then associating them with a solar storm that occurred at a particular date - will allow scientists to date these ancient objects precisely. Eventually, a better chronology of events linked to these objects and these civilisations could emerge.

"In the past, we have had floating estimates of when things may have happened, but tree-rings, these secret clocks, could reset chronologies concerning important world civilisations with the potential to date events that happened many thousands of years ago to the exact year", concludes lead author Dr Michael Dee.