What is development of letters and lettering?

The evolution of writing started with evolution of culture. We might find some of the pictorial writings in the oldest cultures of stone age like 0.5 million years old Samma Soan Valley (Salt Range&Kashmir )culture in South Asia. The oldest writings are found in the pre-historic civilizations of Egypt, Mepotimia, Harappan Civilization in South Asia , China and many other ancient civilizations in EU and Amerca. The Greeks and Romans contributed much in writng systems. Being researcher on secret writing ,codes and ciphers and offered 1st sucessful cryptanalysis model on matured Harappan scripts, I would say that secret writing and use of codes in love is as old as the writngs of ancient civilizaations.