Final answer:
The early Sumerian period is characterized by the development of cuneiform, a sophisticated writing system used on durable clay tablets for recording various aspects of their civilization.
Step-by-step explanation:
A key characteristic of the early Sumerian period of Mesopotamian culture is the development of a sophisticated writing system. The Sumerians created cuneiform, which began as a series of pictographical symbols and evolved into a phonetic script where each symbol stood for a syllable. This invention allowed for the documentation of laws, religious texts, commercial transactions, and literature.
The use of clay tablets, which were durable once baked, was a significant technological advancement for recording such information. Additionally, the early Sumerians were known for their pottery and artistic traditions, as well as their innovation in metalworking.