“It was a bit like a murder case: we have a dead kingdom and we’re looking for the culprit. Step by step, the evidence has brought us closer to the answer.”
Extreme drought contributed to the decline of the ancient southern Arabian kingdom of Himyar. Combined with political unrest and war, the droughts left the region shattered and facilitated the spread of emerging Islam across the Arabian Peninsula, say researchers at the University of Basel report titled ‘Droughts and societal change: The environmental context for the emergence of Islam in late Antique Arabia’ in the journal Science.
Traces of the kingdom of Himyar can still be seen on the high plateaus of Yemen: Terraced fields and dams served as particularly sophisticated irrigation systems to transform the semi-desert into fertile fields. For several centuries, Himyar was a fixture in southern Arabia.
Islam emerged in the Arabian Peninsula in the early 7th century CE after a period of profound societal changes, the research team argues in its paper, enquiring about the environmental context of that emergence. The research team from Basel has presented a hydroclimate record of Southern Arabia showing that droughts plagued the region throughout the 6th century CE.
An important factor
They suggest that increasing aridity and declining agricultural yields may have contributed to demise of Himyar, the dominant power in Arabia at that time.
In the 6th century AD, however, the once-powerful kingdom fell into a crisis, culminating in its conquest by neighbouring Aksum (modern-day Ethiopia). Extreme aridity and declining agricultural yields, may have been a key contributor to the upheavals in ancient Arabia that may have contributed to demise of Himyar, the dominant power in Arabia at that time the researchers led by Prof. Dr. Dominik Fleitmann say in their publication in the journal Science, adding that this could well have also given rise to Islam in the 7th century.
The researchers emphasize that they do not want to say that the drought directly brought about the emergence of Islam. “But it was an important factor in the context of the upheavals in the Arab world in the 6th century.”
Petrified water as a climate archive
Fleitmann team analysed the layers of a stalactite from the Hoti Cave in today’s Oman. The growth rate of the stalagmite and the chemical composition of its layers are directly related to how much precipitation falls above the cave (see box). Thus, the shape and isotopic composition of the deposited layers of a stalagmite represent a valuable climate archive.
“Even with the naked eye you can see from the stalactite that there must have been a very dry period for several decades,” says Fleitmann. If less water drips on the stalagmites, less of it runs down the sides. The stone grows with a smaller diameter than in years with a high drip rate.
The isotope analysis of the rock layers allows conclusions to be drawn about the annual amount of precipitation. The researchers discovered that not only did less rain fall over a long period of time, but that there must have been an extreme drought. The researchers were able to date this dry period to the beginning of the 6th century AD based on the radioactive decay of uranium, but only to an accuracy of 30 years.
Detective work in Himyar
“Whether this drought was directly related to the collapse of the kingdom of Himyar or perhaps only occurred afterwards, could not be clearly proven on the basis of this data alone,” says Fleitmann. He analysed other climate reconstructions from the region and combed through historical sources and worked with historians to better narrow down the time of the extreme multi-year drought.
“It was a bit like a murder case: we have a dead kingdom and we’re looking for the culprit. Step by step, the evidence has brought us closer to the answer,” says the researcher. For example, data on the water level of the Dead Sea and historical documents describing a multi-year drought in the region, dating to AD 520, helped to actually link the extreme drought to the Himyar kingdom crisis.
“Water is the most important resource of all. It is obvious that a decrease in precipitation and in particular several years of extreme drought can destabilize a semi-desert kingdom,” says Fleitmann. The irrigation systems also required constant maintenance and repairs. This could only be accomplished with tens of thousands of well-organized workers. The population of Himyar, stricken by water shortages, was probably no longer able to guarantee this complex maintenance, which further aggravated the situation.
Turning points in history
Political unrest at home and a war spilling over into Himyar between its northern neighbours, the Byzantine and Sasanian empires, further weakened the kingdom. When the western neighbour Aksum finally invaded Himyar and conquered the empire, the once powerful country finally lost its importance.
In Arabia, the first half of the sixth century CE was marked by the demise of Himyar, the dominant power in Arabia until 525 CE. Important social and political changes followed, which promoted the disintegration of the major Arabian polities, the researchers say. They present hydroclimate records from around Southern Arabia, including a new high-resolution stalagmite records from northern Oman that clearly indicate unprecedented droughts during the sixth century CE, with the most severe aridity persisting between ~500 and 530 CE. “We suggest that such droughts undermined the resilience of Himyar and thereby contributed to the societal changes from which Islam emerged,” the team says in its paper published in the journal Science.
“In the case of extreme climate events, one often only thinks of the short period after, limited to a few years,” says Fleitmann. The fact that climate change can lead to the destabilization of states and, as a result, a different course of history, is often ignored. “The need of the population due to hunger and war was great. Then Islam found fertile soil: people were looking for new hope, something that could unite people as one society again. That was what the new religion offered.”
Image: Cross-section of a stalagmite from Hoti Cave in what is now Oman. Holes are from sampling for dating, scratch marks from sampling for isotope analysis. (Photo: Timon Kipfer, University of Basel)