As human societies emerged

As human societies emerged, the development of writing was driven by pragmatic exigencies such as exchanging information, maintaining financial accounts, codifying laws and recording history. Around the 4th millennium BCE, the complexity of trade and administration in Mesopotamia outgrew human memory, and writing became a more dependable method of recording and presenting transactions in a permanent form. In both Ancient Egypt and Mesoamerica writing may have evolved through calendrics and a political necessity for recording historical and environmental events. As languages often evolve independently of their writing systems, and writing systems have been borrowed for languages they were not designed for, the degree to which letters of an alphabet correspond to phonemes of a language varies greatly from one language to another and even within a single language.