Setting the stage: environment and landscape in Mesopotamia

It’s been a while! I’m starting again on converting my class lectures to Historicity posts. Since history begins in Mesopotamia, I will too, by discussing the physical setting of the earliest civilizations. Here’s a map to consult along the way.

The earliest instance of the emergence of complex societies that we would call “civilization” occurred in southern Mesopotamia—aka Iraq south of the river bends at modern Baghdad. Because all ancient civilizations, including that in Mesopotamia, were shaped in so many ways by the geographies and environments in which they arose, I’ll begin by describing the major components of the physical landscapes of the different regions of the Near East.

The word Mesopotamia means “between the rivers.” The two rivers in question were the Tigris on the east and the Euphrates on the west. These rivers are important to southern Mesopotamia in two major ways:

First, they have created the landscape of southern Mesopotamia by depositing layers and layers of silt which has created a very flat plain between the river levees, a plain which gets flatter the further south it goes.

The silty nature of the soil here makes it vulnerable to a second major landscape-shaping force: wind erosion, which to some extent counteracts the deposition of silt on the plain. The effects of wind erosion is quite variable from place to place, which can be seen in the extent to which ancient archaeological sites have been covered in silt. Some sites are covered with several meters of silt; while at others, the wind has scoured away the silt surrounding sites, so that the earliest level of the site is actually higher than the level of the surrounding plain. These early levels were protected from erosion by later levels of building, which protected the early levels.

Wind erosion can also create large dunes of accumulating wind-blown silt, which can also obscure ancient sites. This problem is exacerbated by the salinization of cultivated land, which I will discuss further in a minute. These dune belts are fairly fast moving, but can still cover ancient sites for several decades at a time.

Second, the two rivers are necessary as providers of irrigation water for farming in southern Mesopotamia. Agriculture is not possible without irrigation in this region, thus the rivers and the maintenance of systems of irrigation and drainage were vital to ancient and modern societies in Mesopotamia.

You can see on the map that the Euphrates river is much longer than the Tigris. In addition to being shorter and following a less winding path, the Tigris has a steeper gradient than the Euphrates and flows much faster. The Euphrates travels more slowly, and traverses a wide expanse of steppe and semi-desert in Syria and northern Mesopotamia. These factors cause the rivers to be rather different in character once they reach southern Mesopotamia:

The Euphrates is higher in silt content than the Tigris, and in southern Mesopotamia the deposition of this silt has caused built up the levee and bed of the Euphrates until it actually flows above the level of the surrounding plain. To irrigate, farmers need only to cut through the levees and let the water flow out. The faster-moving Tigris, on the other hand, has cut into the silt so that it flows below the plain, and water has to be lifted up and out to use the Tigris for irrigation water. Thus the Euphrates is much easier to use for irrigation.

The picture is not altogether rosy, however. There are two major problems with the use of river water for irrigation:

First, before modern dams and such controlling mechanisms were built, the rivers flooded annually. In Egypt, the Nile River also flooded annually before modern dams were built to regulate the flood waters. Luckily for the ancient Egyptians, the floods came at the best time in the agricultural cycle. In Mesopotamia, however, the floods arrived in April or May. Since in Mesopotamia crops were grown in the winter, since the summer is too hot; the floods arrived just at harvest time when they could potentially destroy the crops.

Second, the waters of both rivers, and especially the Euphrates contained a significant amount of dissolved salts. If irrigation water was allowed to stand in a field, the soil could become salinized & thus unusable for cultivation of crops.

Therefore, while irrigation was necessary for agriculture in southern Mesopotamia, a significant amount of maintenance had to be done to effectively use the river water for irrigation. The levees had to be maintained to prevent the floods from breaking through and destroying the crops. To prevent salinization, drainage systems had to be maintained, and a system of letting the land lie fallow had to be observed—which means that after growing crops in a field, the field couldn’t be used to grow crops again for several years to allow the accumulated salts to wash out and the water table to subside to its accustomed level.

Another problem with dependence on the Euphrates and Tigris is that the rivers occasionally changed the channels through which they flowed. The Tigris kept more or less to a single channel, but the nature of the Euphrates was different—it consisted of multiple channels which interwove and frequently shifted. This caused serious problems for cities that were situated along the abandoned channels.

These two problems, salinization of the land and shifting of river channels, led to periods of desertification and abandonment in southern Mesopotamia.

Areas away from the rivers: Away from the few miles of cultivable land along the river banks, there is not enough moisture for farming, although flocks of sheep and goats could be taken there to graze.

To the north and east of the alluvial plain were foothills and mountains. The foothills and some intermontane valleys in this region received enough rain for dry farming. The Zagros Mountains were a barrier to travel to the east. To travel east to Iran, the most common route was north along the Tigris, east along its tributaries and south again; there was also a passage through the marshes along the Tigris to the south. The mountains contained important resources such as timber for building and metal and stone; none of which existed on the alluvial plain.

In the southernmost area of southern Mesopotamia were extensive marshes, which extended northwards along the Tigris. During some of the periods of abandonment of cities in southern Mesopotamia, dynasties of kings based in these marshes appeared. In addition to these permanent marshes, temporary marshes would have appeared with each spring flood and evaporated during the summer. Ancient texts mention marshes near many ancient cities; these were apparently valuable for the resources they provided. Administrative texts record birds, bird eggs, turtles, and fish gathered from the marshes for use in cities.

There has been some debate about the location of the Persian Gulf coast in ancient times. A theory in the early 20th century suggested that the gulf coast had been gradually built out by silt deposition over the millennia; while a later theory suggested that subsidence of the underlying tectonic plate under the weight of the silt counteracted the effect of siltation. More recently, this view has been questioned; and many geomorphologists now believe that the Gulf coast has retreated 150-200 km to the southeast since 4000 BC, and that during the early parts of the formation of urbanization in Mesopotamia, the gulf encroached further inland in a shallow tidal environment.

The climate has probably not changed much since antiquity, although small-scale changes probably had significant effects from time to time. Summer in the alluvial plain of southern Mesopotamia is dry and extremely hot. Winter rains fall sometime between October and April, when the weather is cooler. Crops were grown in the winter, as summer was too hot and dry for agriculture. During summer there are also sandstorms and duststorms.

Natural resources: While the irrigated fields of southern Mesopotamia produced fairly high yields of crops, the region had few other natural resources. It contains no local resources of several materials which played important roles in Mesopotamia’s urban societies: these included metal, timber, semiprecious stones, and stone usable for building. These were, however, available in the Taurus and Zagros mountains, and in different periods Mesopotamian kings or private individuals accessed these resources through trade with the local peoples. The Euphrates River provided a convenient corridor for transportation to Anatolia, and from Anatolia, Mesopotamians acquired obsidian, copper and tin which were used for making bronze, gold, silver, and other resources.

Next, I’ll write about the two cultures which represent the beginnings of urbanization and “civilization” in southern Mesopotamia: the Ubaid and Uruk periods.

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