How mummies help us understand the climate in ancient Egypt

In Ancient Egypt, especially during the period of Roman rule starting in the year 30 B.C., mummies were transported to the necropolis on a wooden funeral slab, known as a mummy label. It typically included engravings of information about the deceased, like their age, profession, city of birth, mummification method and burial place. As the labels became a funerary custom in the Hellenistic era, the inscriptions were typically written in Greek, Demotic or both languages.

The labels functioned to identify the body when it reached the embalming workshop and when it was moved to the necropolis. In a more transcendental sense, they were thought to accompany the deceased to the afterlife. It was common to engrave a brief religious inscription or a religious symbol to guarantee their continued wellbeing.

Thanks to Egypt’s arid climate, the objects are often found today in a well-preserved state. They have been studied for years to better understand the society that created them. But recently they have attracted the interest of researchers for another, better-kept secret that they contain. Each year, trees form a ring inside their trunks, the characteristics of which vary according to the climate. Since the mummy labels are made of wood, they have preserved valuable environmental and climate information from their era, going far beyond their original function.

Now, a group of Swedish scientists is trying to use the wooden planks to reconstruct the climate of the western Mediterranean at the time of Roman Egypt. “Trees are archives with a lot of information, like the impact of the climate on their growth and dry episodes,” explains François Blondel, a researcher from the University of Geneva and one of the leaders of the study.

As Blondel explains, the key to reconstruct the climate of the past lies in the width: thicker rings indicate faster growth, in years with greater rainfall, and narrow ones indicate a year of drought. The comparison of growth ring patterns from different species can reveal climate fluctuations over the years. “To simplify it: a wide ring can express an adequate climate and environment, and a narrow ring the opposite, a bad climate or environment,” says the investigator, who explains that they work “to recreate the climate through the variations of ring width in samples from the same geographic zone and the same species.”

The researchers have analyzed more than 1,700 of these wooden slabs. In 451 cases, they have been able to identify the tree species, some of which grew in Egypt and others that were imported from elsewhere, including the Iberian Peninsula. The most common species were cedar, pine, fig trees, and bushes from the Tamarix genus. Cypress, firs and olive and beech trees also appeared.

Of all the wooden slabs analyzed, the growth ring patterns of their trees are studied in 242 cases, of which 80% had fewer than 50 rings, 18% between 50 and 100, and 2% with more than 100. Though the sample is not yet sufficient to recreate the climate of Roman Egypt and the eastern Mediterranean, the researchers believe that it offers a valuable first glimpse. “Their quantity is a starting point, though it is still small,” Blondel says.

The advantage, in this case, is that thousands of mummy labels are conserved in museum collections all over the world. The Louvre in Paris alone has 852 of them. Although the samples each have few rings, in some cases, they can be interpreted in series when it is determined that multiple plaques have the same origin.

“Together, several dozen plaques have more than 100 rings,” François Blondel says. “And now the acquisitions have broadened to other collections, like mummy portraits, sarcophagi and larger everyday objects, which are less common in museums, but which tend to have larger series of rings. It is a work in progress,” he adds.

“Even if we can’t pin down the Egyptian climate, we will get at least a trend of notable climate episodes in a large part of the eastern Mediterranean,” Blondel explains. “As the study is still in progress, it is still difficult to give a precise answer, but a climate trend in a larger geographic zone would be a first indicator to understand the impact of the climate on this part of the Roman Empire.”

The researchers explain that the analysis can be useful not only to detect climate trends over an extended territory, but also to better understand the many events that marked the history of Roman Egypt and the Roman Empire across the region, including its episodes of prosperity and crisis.

“We should keep working on other collections of wood from Roman Egypt, and extend to other territories, particularly those where the wood imported to Egypt originated. The territories of the eastern Mediterranean basin are prioritized: Turkey, Cyprus, Lebanon, Syria, Greece,” Blondel says. “This study is just beginning, and there is a lot of wood left to study to gather the references that are the necessary basis of our climate reconstructions.”

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