What is the earliest example of proto-writing that dates to the Bronze Age?
Proto-writing
The transition from proto-writing to the earliest fully developed writing systems took place in the late 4th to early 3rd millennia BCE in the Fertile Crescent. The Kish tablet, dated to 3500 BCE, reflects the stage of "proto-cuneiform", when what would become the cuneiform script of Sumer was still in the proto-writing stage. By the end of the 4th millennium BCE, this symbol system had evolved into a method of keeping accounts, using a round-shaped stylus impressed into soft clay at different angles for recording numbers. This was gradually augmented with pictographic writing using a sharp stylus to indicate what was being counted. The transitional stage to a writing system proper takes place in the Jemdet Nasr period (31st to 30th centuries BCE). A similar development took place in the genesis of the Egyptian hieroglyphs. Various scholars believe that Egyptian hieroglyphs "came into existence a little after Sumerian script, and... probably [were]... invented under the influence of the latter...",[7] although it is pointed out and held that "the evidence for such direct influence remains flimsy" and that "a very credible argument can also be made for the independent development of writing in Egypt..."[8] (See further Egyptian hieroglyphs).
Prehistory
Sumer in Mesopotamia, the Indus valley civilization and ancient Egypt were the first civilizations to develop their own scripts, and to keep historical records; this took place already during the early Bronze Age. Neighboring civilizations were the first to follow. Most other civilizations reached the end of prehistory during the Iron Age. The three-age system of division of prehistory into the Stone Age, followed by the Bronze Age and Iron Age, remains in use for much of Eurasia and North Africa, but is not generally used in those parts of the world where the working of hard metals arrived abruptly with contact with Eurasian cultures, such as the Americas, Oceania, Australasia and much of Sub-Saharan Africa. These areas also, with some exceptions in Pre-Columbian civilizations in the Americas, did not develop complex writing systems before the arrival of Eurasians, and their prehistory reaches into relatively recent periods; for example 1788 is usually taken as the end of the prehistory of Australia.