I have thought about it a lot, read books about it, done scientific research, traveled, and a lot of listening. I think it started as a way to get a mate, and for defense. Later it became more, in my view. I know that language is the exchange of ideas. Words are pictures in the mind. Some languages don't have words but pictures instead. Chinese, for example. A letter is a picture of a sound.

Hi... This explanation is about how writing language started : Early Mesopotamian writing was found in trade, business and farm records which have led many to believe for a long time that this is where the written word originated. Along with this belief, it has also been thought that since Mesopotamia traded extensively with ancient Egyptian and ancient Indian civilizations that the idea of writing could have spread to these other cultures. Recent discoveries, however, are undermining ancient Mesopotamia’s status as the origin of writing. In 1998, a German archaeologist discovered writing at the tomb of King Scorpion the First in Abydos, near Luxor, in Egypt. He says that this writing dates back to 3400 B.C., a few hundred years before the earliest known Mesopotamian writing. The writing was discovered both on pottery and clay tablets. In 1999, American archaeologists digging at the ancient site of Harappa in Pakistan discovered what they say is writing that dates back to around 3500 B.C. Harappa was at that time a major city in the ancient Indus Valley civilization which dominated western India, Pakistan and Afghanistan. While both early Mesopotamian and Egyptian writing is clearly related to trade, the ancient Indus script has still not been deciphered. While neither the ancient Egyptian nor Indus discoveries conclusively prove that one civilization can claim to have invented writing, these discoveries suggest that writing developed simultaneously and perhaps independently in a number of places. Indeed, it might well be that even earlier forms of writing are found in the coming decades. We are finding that the earliest cities may have developed thousands of years before these writing specimens. Because writing seems so closely tied to the rise of trade and human settlement, it is quite possible that many new discoveries await archaeologists searching for the origin of this most critical of human skills.

I don't know I have never thought of that .. do you know how ?