About 4,200 years ago, the first empire of Mesopotamia, the Akkadian fell, coinciding with major transformations in Egypt and the Indus Valley, the two other great civilizations of the time. A study of stalagmites in Iran suggests that a generalized climatic event may have been responsible for all three.
Civilizations arise and fall for many reasons, and the causes of the death of the Acadian Empire remain controversial. The coincidence of time with distant events has led some historians to propose a climatic cause. The nature, and even the existence, of this event is not clear, however, as happened in the middle of the Holocene, with practically steady temperatures, with no increase in volcanic activity or change in solar production.
However, when a team led by Dr. Stacy Carolin of the University of Oxford studied a stalagmite of the Gol-e-Zard Grotto in the Alborz Mountains of Iran, formed between 5,200 and 3,700 years ago, they certainly saw something happen in the time. The team report in the Proceedings of the National Academy of Sciences had sharp peaks in the amount of magnesium compared to calcium 4,510 and 4,260 years ago, coinciding with slower growth and changes in the stone's oxygen isotopes. These changes lasted 110 and 290 years, respectively, before the composition of the stalagmite returned to previous levels.
The industry and mining of ancient civilizations have sometimes left their mark on the planet, but we know of no mechanism by which the Acadians could have impacted such distant caves. Therefore, it seems likely that whatever was causing the chemical change overthrew the Akkadians, rather than their fall, by altering the chemistry of the distant caves.
The change in stalagmite composition appears to be the result of increased dust falling into the mountains, which in turn appears to be a consequence of drier conditions to the west. Today, the dry years in the deserts of Syria and Iraq are associated with increased dust deposition in Tehran, just 50 kilometers (30 miles) from Gol-e-Zard. Stalagmite slow growth may also be a sign of locally drier conditions.
Sediments from the Red Sea and Gulf of Oman, among other paleoclimatic proxies, were previously used to suggest that western Asia experienced at least one great dry period at this time, but the dating to these was too imprecise to link them with confidence to the Akkadian. collapse. The stalagmites, on the other hand, have an error of only 31 years.
There is a great debate among historians about how much climate change has contributed to the collapse of civilization – which has become warmer as it becomes more relevant to us. We do not know why Mesopotamia dried up during this period, but it seems that it overturned one civilization and seriously affected two others.