The earliest form of symbolic communication was probably some form of speech or gesture. Although the most primitive forms of spoken language may have been onomatopoeic, most spoken language consists of symbols, in that the relationship between signifier (sound) and signified (what a sound means) is arbitrary. Because this early development of speech occurred before recorded history, analysis of it is hypothetical.
The earliest visual symbols we find are pictographs and cave paintings. Since these types of proto-writing have not been deciphered, we can only surmise that some elements were representational and some symbolic. Other early forms of symbolic communication were tally sticks, used to help record quantitative information.
The direct precursors to ancient Mesopotamian writing were seals and tokens, used to identify two things, ownership or identity (in the case of seals) and contents of closed containers (in the case of tokens). True writing evolved out of abstract representation of tokens in ancient Sumerian, and gradually moved from a limited number of ideographs to a complex syllabary.