The Uruk Period's geographic center was in the extreme south of Mesopotamia, particularly at Uruk. Diagnostics of the Uruk Period are: beveled-rim bowls, cylinder seals and mosaics. Beveled-rim bowls were a mass-produced bowl which first appeared in the Early Uruk period, part of the larger shift toward mass-produced undecorated utilitarian wares rather than the unique and careful pieces of early eras. Cylinder seals first appeared in the Late Uruk period.
Settlements grew throughout southern Mesopotamia, with the biggest and most active being Uruk. Uruk was advantaged by the variety of nearby ecological niches. Uruk was just inland from the Persian gulf, placing it near the marshes which provided fish and fowl, and where water buffalo were herded for milk. Also nearby was the Euphrates (and its branches), from which Uruk derived irrigation to abundantly cultivate cereals and orchard fruits, especially dates.
The various foods from various niches led to specialization among producers: fishermen, farmers, gardeners, hunters and herdsmen. These producers were more effective when they devoted most of their time to a single form of cultivation, especially with the advent of the seed-plow which allowed faster planting but required the hand of an expert. These people were no longer self-sufficient, and they needed the system of exchange which grew at Uruk.
Early Uruk Period
4000 - 3500 BC
Throughout the ancient Near East, the carefully fashioned and decorated vessels of the previous cultures were replaced by rough and undecorated wheel-made plates, bowls and jars which seem to be purely utilitarian. This was likely a shift in the attitude toward these utensils rather than the arrival of a new population. The beveled-rim bowl first appears at Eanna XII, a shallow bowl which was crudely made in a mold in a limited number of standard sizes (perhaps used for rationing) and discarded by the thousands, sometimes even still intact. The beveled-rim bowl is a telling diagnostic of an Uruk Period site.
Uruk → Late Uruk
Urban growth exploded, particularly in the south of Babylonia at and around Uruk. The center of Babylonia underwent a negligible increase in permanently settled population and is attributable to natural growth.
Late Uruk Period
3500 - 3100 BC
In the south around Uruk, there was an enormous escalation in the area occupied by permanent settlement from 81 to 210 hectares. This was largely in Uruk, which was now 100 hectares itself, as it was a true urban center surrounded by a set of secondary settlements. The city revolved around the temple organization, an entity within which specialist producers lived and contributed their output, in exchange for security and rations.
The Late Uruk Period heralded the first cylinder seals, which would become characteristic of Mesopotamia throughout its entire history. From the start, cylinder seals were highly elaborate and required more mastery than the stamp seals which had existed since the early Neolithic. Not coincidentally, the Late Uruk Period shows the first monumental art, relief and statuary in the round, made with such a degree of mastery that only a professional could have made them.
In ~3,200-3,000 BC, urbanized Sumerian colonies along trade routes expanded Uruk culture. In north and central Syria, west of the Euphrates, this influence was weak and urbanization congealed slowly; in northeast Syria, in the upper Khabur and Balikh river basins as far as the upper Tigris, a stronger Uruk cultural influence led to a more cohesive territorial system.
During the secondary urbanization that swept the Southern Levant in the middle of the 3rd millennium BC, areas untouched by urbanization became proto-urban.
The transition to full urbanization in upper Mesopotamian sites was as early as ~2,600 BC when Early Dynastic III in Mesopotamia began. Simultaneously, after centuries without communication, intense cultural interaction formed between these northern areas and southern Mesopotamia. Cities that participated in this development, albeit at disparate times and degrees, included: Tell Taya in the Wadi Tharthar; and Tell Leilan (ancient Shekhna/Shubat-Enlil), Tell Brak and Tell Mozan in the Khabur triangle.
Origins of cities
A fundamental element in the Mesopotamian ideology regarding cities was the concept that each was the dwelling of a particular god or goddess. Cities were thought to have been constructed in primordial times for the gods, each of whom acted as their patron deities, e.g., Nanna for Ur, Inanna for Uruk, or Enlil for Nippur. This concept was linked to the role of the temple, or god's household (see below), in cities. The temple's function as collector and distributor of agricultural resources was founded in the ideology that the god received them as gifts and redistributed them to the people. Thus the head of the temple administration served as leader in the city, and from the Uruk period on the primary ideological support for the city-ruler was his function in the temple household. The temple was, in fact, the dominant institution in the early city and the largest structure within its walls, sometimes built on an earthen platform towering over the other buildings. The gods were imagined as living in a world parallel to that of humans, so each god had a household, spouse, children, and servants. These dependent deities also had smaller temples and shrines in the cities, sized according to their status, and each city had a multitude of temples. Mieroop, p 45 - 46
Two ways of life were established by the Late Uruk period. In the countryside were agriculturalists who were free but uninsured against natural disasters. In the city were administrators, artisans and laborers who relied on the the temple organization by performing a certain task for the temple and receiving sustenance and protection in return. However, the temple was the focal point for everybody -- it was the biggest structure; it was the center of a shared ideology; and it received tribute from all.
There was little social stratification in the countryside, beyond that within the individual family. These people likely provided part of their income/goods to the temple, but were otherwise free and worked their own land. However, within the city was an entirely different way of life which centered around the temple. Specialist workers contributed their output to the temple, and in exchange received sustenance and protection. The temple organization was self-sufficient, complete with fields and workshops.
The temple organization, with many of the functions of a small state, brought with it social stratification. The Standard List of Professions lists professions hierarchically. The highest official was a sort of priest-king who led the temple and was a liaison between the temple dependents and the god/dess. Beneath him were administrators -- leader of the city, leader of the plow, great one of the cattle pen, great one of the lambs, etc. At the lower ranks were producers, both agricultural and otherwise.
These producers performed the tasks which had once been performed within the family. There were potters, as indicated by mass-produced wares such as beveled-rim bowls. There are depictions of textile-weavers, mostly women; it was a back-breaking labor, and some female skeletons have the associated arthritis and deformations. Smithers are indicated by a potential smelting workshop at Uruk, where channels were lined with ~50 cm deep holes alongside them; metal would be scooped up and poured into molds in the holes. Starting in the Late Uruk period, the advent of cylinder seals and advanced lithic art necessitated expert stonecutters.
Uruk IV tablets contain accounts of grain distributed to workmen; these seem to be precursors of later ration lists. The issuing of rations to numerous people may explain the abundance of bevel-rim bowls, whose limited number of sizes would have made them ideal for measuring barley rations. Further, the early cuneiform sign for ration (NINDA) resembles a bevel-rim bowl. If this is correct, then the first bevel-rim bowls of the mid-fourth millennium attest to a grain distribution system already in place at that time.
Continuing a trend begun in the early Ubaid period, the temple buildings of the late Uruk period became the biggest structures in the settlement. The earliest monumental temples of the Eanna district were built in the Late Uruk period. The great labor expense of building the temples reflected their prominent societal role. Two simultaneous temple complexes existed at Uruk, the Eanna temple complex (née Eanna precinct) and the less-explored Anu-ziggurat (née temple tower). The Uruk Vase was found in a cult deposit from Uruk III and pictorially expresses the role of the Eanna temple complex in Uruk society: a place for goods to collect as offerings to the goddess Inanna.
The Uruk Vase depicts nude offering-bearers led by a human, larger in height and dressed ornately -- this figure is titled EN (Sumerian for lord) and is likely the head of the temple, a sort of priest-king. He faces the goddess Inanna, a female figure identified by two adjacent reed bundles, which served as door posts at the time and became the cuneiform for her name.
Writing and Administration
Accounting provides two sets of data: the authority over the transaction; and the amount transacted. Authorities in transactions were able to indicate themselves without writing. From the seventh millennium on, individual entities used their own unique stamp seals to tag containers. In the middle of the Uruk period, the stamp was replaced by the cylinder seal. The cylinder seal could simply be rolled, enabling speedier coverage of surfaces. The discovery of countless different seals attests to a class of officials in Uruk who supervised transactions and guaranteed their legitimacy by attaching their mark of authority.
However, seals do not disclose the quantity or contents in a transaction. Several techniques to record this information were tried out at the same time or in quick succession. The stratigraphy at Uruk is indecipherable. At Susa, the first bullae date to a layer just before Uruk IV. Bullae were hollow spheres containing tokens. Tokens were little clay or stone objects denoting the quantities in a transaction; the outer sphere was impressed with seals, so that breaking and tampering would be clearly evident. For instance, the receipt of three units of barley could be denoted by three tokens sealed in a bullae.
Unfortunately, the contents of a bullae could not be verified without destroying it. Thus, the idea arose to impress the outside surface of the bullae, likely with the inside tokens. Simultaneously, there appeared solid tablets onto which numerical signs were traced. This was the first invention of writing; it was a way to communicate quantities and contents in transactions. By the end of the Uruk period, a system of signs had developed were written in proto-cuneiform.
This preceded true cuneiform and was different only in that the former was drawn into clay with thin lines rather than pressed into clay with wedges.
Numerical tablets were found at Uruk and other sites where Uruk influence extended. They told what items were being counted (sheep, humans, grain, etc) based on the units themselves. Different counting systems were used for different items. While this was clear to the people using them, it has left ambiguity for modern scholars. Only at Uruk itself and in Susiana do records appear with additional clarification: numbers were combined with one or two signs indicating what was involved.
The two regions' shared system quickly diverged into distinct and independent systems of true writing. Proto-cuneiform script first appears at Uruk IVa and III, while somewhat later in Susiana there appeared proto-Elamite.