Around 1,500 years ago, southern Arabia was hit by a multi-decade megadrought, a new study of ancient climate data has found. This likely contributed to the downfall of a once powerful Jewish kingdom that ruled over large swaths of what is today Yemen, Oman and Saudi Arabia.
The demise of the ancient kingdom of Himyar in the sixth century and the ensuing power vacuum in Arabia may have then favored the rise and expansion of Islam throughout the region less than a hundred years later, suggests the paper published Thursday in Science.
The discovery of the drought sheds some light on the roots of the social and political chaos of pre-Islamic Arabia, and also sounds a warning for modern times (if there was still a need for that) about how climate change can quickly bring even the most sophisticated civilization to its knees.
“We are not saying that the drought was the only factor, but it may have contributed to and amplified existing social and economic problems, helping create the perfect storm that led to the demise of Himyar and the emergence of Islam,” says Professor Dominik Fleitmann, a geologist from the University of Basel in Switzerland and the lead author on the study.
The Himyarite kingdom was founded in the late second century B.C.E. in today’s Yemen. It gradually extended its control over most of southern Arabia by onquering neighboring states, including Saba (or Sheba), the ancient kingdom whose queen of biblical fame supposedly visited King Solomon.
During the fourth century C.E. the Himyarite elites abandoned their ancestral polytheistic beliefs and converted to Judaism, followed by an unknown percentage of the broader population.
The choice of Judaism as a state religion may have been a way to maintain neutrality among various rival regional powers: the Christians of the Byzantine Empire and of the kingdom of Aksum in Ethiopia, as well as the Zoroastrians of the Persian Empire. All these powers eyed the lucrative spice trade of Arabia that enriched Himyar and they eventually played a part in the kingdom’s demise.
Until the sixth century, Himyar managed to fend off foreign encroachment, but around 525 it suddenly fell to an invading Ethiopian force. But what happened? Inquisitive geologists and archaeologists wanted to know whether there were other factors behind the downfall.
To answer that question, Fleitmann and colleagues recovered ancient climate data from a stalagmite in Hoti Cave, in northern Oman. Stalagmites and stalactites, which form over thousands of years from minerals deposited by water dripping into caves, contain a record of past precipitation in their growth rings – not too differently from trees.
In very rainy years, more water penetrates underground and the formation grows more: vice versa with dryer years. The amount of rain also changes the proportion of oxygen isotopes that are found in the stalagmite.
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So, after dating the rings in the stalagmite by looking at the decay of uranium and thorium isotopes, researchers can approximate how much it rained in each particular year by looking at the chemical composition of the rock’s layers.
In the case of the stalagmite from Oman, which started to form some 2,600 years ago, the researchers found evidence of severe drought between the years 500 and 530. Precipitation levels dropped to less than half their modern average, creating what may have been the worst drought in southern Arabia over the last 10,000 years, Fleitmann says.
Southern Arabia gets a yearly 50 to 255 millimeters of rain from a combination of winter rains and summers monsoons. That’s not much, but it was enough to sustain agriculture in ancient Himyar.
In fact, in the same period, there were prosperous Byzantine farming towns in the Negev desert, in today’s southern Israel, which gets even less precipitation. The Himyarites managed their scarce water sources expertly with terraced fields and an elaborate irrigation system, whose crown jewel was the famed Marib Dam.
Built by the Sabeans in the eighth century B.C.E. and then periodically restored and enlarged by the Himyarites, this 650-meter-long and 15-meter-high dam was used to collect monsoon runoff and irrigate fields that covered up to 100 square kilometers.
But even these advanced systems couldn’t sustain agriculture in such a prolonged and extreme drought. The analysis of the Hoti stalagmite is compounded by historical records and data from other points in the Middle East, which tell us that the drought affected the entire region, causing the Siloam spring in Jerusalem to dry up in the 520s, and dropping the levels of bodies of water from the Dead Sea in Israel to Neor Lake in northern Iran, the researchers report.
“At that time Himyar possibly had one of the most efficient and advanced irrigation systems in the world, much like Israel has today,” Fleitmann notes, adding that his team’s findings carry an important message for a modern world that faces increasing drought conditions caused by human-made climate change. “Despite having all these technologies, there always comes a moment where you reach a tipping point, when the climate is too bad and the rainfall too low,” he says.
The geologist doesn’t believe the megadrought was the only cause of Himyar’s demise but given the baggage of famine, migration, unrest and conflict that such events generally bring with them, it most likely was a contributing factor in leaving the kingdom weak and vulnerable.
For example, ancient chroniclers relate that the last Jewish king of Himyar persecuted his Christian minority, massacring part of the Christian population of Najran, in today’s Saudi Arabia – an act which in turn was seized upon by the Aksumite Ethiopians as a justification to invade.
As often happens in history, it is possible that those persecutions were sparked by the social and economic crisis brought on by the drought, Fleitmann speculates.
After the Aksumite conquest in 525, Himyar enjoyed a brief revival in the mid-sixth century under Abraha, an Ethiopian general who fancied himself a king and declared independence from Aksum. Possibly aided by a letup in the drought conditions, Abraha expanded his domain into central Arabia, reaching as far as Mecca and Medina.
But based on the stalagmite data from Oman, the water scarcity returned in the last decades of the sixth century. In a final blow to Himyar’s prestige and economy, the monumental Marib Dam collapsed around 570 and ceased to function. This event was so catastrophic that it was later mentioned in the Quran, framed as a divine punishment for the locals.
Indeed, there was a sign for the tribe of Sheba in their homeland: two orchards—one to the right and the other to the left. They were told: “Eat from the provision of your Lord, and be grateful to Him. Yours is a good land and a forgiving Lord.” But they turned away. So We sent against them a devastating flood, and replaced their orchards with two others producing bitter fruit, fruitless bushes, and a few sparse thorny trees. This is how We rewarded them for their ingratitude. Would We ever punish anyone in such a way except the ungrateful?" (Quran, 34: 15-17)
By the way, it is not surprising that the dam was seemingly destroyed by a flood in the midst of a megadrought, Fleitmann tells Haaretz. Droughts tend to dry and harden the topsoil, making it less absorbent and transforming an occasional downpour into a flash flood powerful enough to punch through walls, he says.
A new hope
With Himyar definitely out of the geopolitical picture, the Byzantine and Persian empires were now free to vie for influence over southern Arabia and its rich trade in myrrh and frankincense. But very quickly these two powers would also cripple each other in a long and bloody conflict from that lasted from 602 to 628.
All of these events ultimately set the stage for the emergence of a new religious and political identity in Arabia, Fleitmann says. The crisis in southern Arabia increased the importance of economic and pilgrimage centers further north, such as Mecca and Medina.
With the economic turmoil and political fragmentation of the period it was only a matter of time until the tribes of Arabia united under a new leadership, which they ultimately found in the prophet Mohammed and his successors from the 620s onward.
“The population was experiencing great hardship as a result of starvation and war,” Fleitmann says. “This meant Islam met with fertile ground: people were searching for new hope, something that could bring people together again as a society. The new religion offered this.”