Hundreds of clay tablets marked in cuneiform have been found in excavations of the Sumerian city of Uruk (in present-day Iraq). Though the tablets date from roughly 3000 B.C., the writing on them uses relatively few pictographs; instead, numerous abstract symbols are used. The sign for "sheep," for example, is not an image of a sheep, but rather a circled cross, while the sign for "metal" is a crescent with five lines. Because of its early date, this seemingly sudden appearance of such abstract writing has long puzzled researchers. At the same time, among prepottery clay artifacts found at archaeological sites along the Jordan and nearby rivers are thousands of small, hand-modeled tokens of fired clay, some dating to before 4000 B.C. Often ignored by archaeologists—some concluded without evidence that they were amulets or game pieces—the tokens are identified by Denise Schmandt-Besserat in her book Before Writing (1992) as overlooked predecessors to the written word.

The earliest of the tokens were simple in form—small cones, spheres, and pyramids—and they were often inscribed. In 1966, a hollow tablet containing several of these tokens was discovered, and more than 100 additional tablets, which are now recognized as sealed envelopes of clay, have since been found. Later envelopes are also inscribed with impressions of tokens in the outer clay, signaling exactly what each envelope contained. Noting that these inscriptions are clearly traceable to later, known inscriptions of farm products, Schmandt-Besserat theorizes that the envelopes contained official records of villagers' contributions to temple-based grain and livestock pools. After 4000 B.C., hundreds of new token forms developed, as a rise in industry boosted the token system. Many forms are figurative, such as bowls or jars with handles, suggesting that villagers' crafts were becoming more diversified and sophisticated.

The token system, essentially a system of three-dimensional nouns, was replaced in about 3100 B.C. by a system of marks on clay tablets. A few centuries later, this latter system was to display the first use of numerals, where simple marks coded the concepts of one, two, and so forth. The eventual evolution of this system into mature writing, Schmandt-Besserat suggests, can be seen in the following example: At first it took two ovoid tokens to record two jars of oil. A little later, it took two markings on a clay tablet to achieve this—one mark, using the outline of the old token, to record the customary unit measure for oil, the jarful, and a second mark to convey the numeral: two oil jars. Eventually, it took three signs on the tablet, one for the numeral 2, one for the standard jarful, and a new symbol that denoted oil itself. With three such signs, an abstract and flexible written form had arrived.