The early writing systems that emerged in Eurasia in the early 3rd millennium BC were not a sudden invention. Rather, they were a development based on earlier traditions of symbol systems that cannot be classified as writing proper, but have many characteristics strikingly similar to writing. These systems may be described as proto-writing. They used ideographic and/or early mnemonic symbols to convey information yet were probably devoid of direct linguistic content. These systems emerged in the early Neolithic period, as early as the 7th millennium BC.