Writing as we know it today did not spring fully formed from the mind of some ancient genius, but was independently developed over hundreds of years in the various civilizations of the early Earth. The development of vastly different writing systems follows a surprisingly similar path in the various cultures which developed them.
The forerunners to writing systems are pictograms in every culture. When early people wished to convey an idea in a permanent medium, they simply drew the concept. Examples of drawings by the first human beings can be found all over the world in the form of cave art. However, as certain symbols became more and more common, it became unnecessary to draw the concept precisely - broad strokes would convey the idea sufficiently.
This led to development of pictographs, small, common pictures used to describe a series of ideas. For example, to write "The man ran to catch the mammoth," it sufficed to draw a man running with a spear next to a mammoth. However, such a system lacks the preciseness of modern writing.
In other cultures, abstract symbols were developed for verbs and for nouns not easily drawn. Such a culture is frequently said to write with hieroglyphs, although this word is generally not used for the Chinese system, although it fits this description.
Once a pictogram system developed to the point of being able to express all or most of the concepts which could be expressed through vocal language, it ceased to be a pictogram system and became a writing system. If the pictrograms continue to represent concepts, then the writing system frequently becomes logographic. If all the symbols represent individual sounds, then the writing system becomes alphabetic.
The earliest language was that developed in the "fertile crescent," which is modern-day Iraq. The Sumerian and Babylonian civilizations which lived there developed a writing system known as cuneiform. Cuneiform appears to have developed as a tallying system developed for commercial trade. As the economy of the region diversified, it became necessary to keep track of transactions, as well as to write contracts and legal codes.
As the tallying system used by the early Sumerians became more complex, the cuneiform symbols began to represent individual sounds, which came from the first sound of the word they once represented.
One of the earliest complete documents we have is the Sumerian King List, which listed the kings of ancient Sumer. This list provides extra-biblical evidence of an ancient flood which covered the entire Earth.
Unlike many writing systems of the ancient world, the clay tablets that cuneiform tended to be written on can survive for thousands of years. We have a personal letter from a queen to a king dating from the third millennium BC. Some dating techniques place this letter at 2400 BC, over 150 years before the Tower of Babel, when Sumerian was the only language in the world. See picture.
Ancient Egyptian hieroglyphs form the basis for many modern writing systems, due to the influence of Egypt in the ancient Mediterranean. While Egyptian hieroglyphs appear to have developed from earlier Egyptian pottery art, cuneiform in the neighboring Babylon developed first, and it is probably that Egyptian merchants would have been introduced to cuneiform before the development of hieroglyphs, so a Sumerian influence is likely.
Unlike alphabetic systems, Egyptian hieroglyphs are logographic. Unusually, the number of symbols increased over time: while there were only 800 symbols during the "ancient" period of Egyptian civilization, after the Hellenistic conquests, there were over 5000.
Egyptian hieroglyphs were mostly forgotten by the Western world until Napoleons exploits in Egypt brought back many inscriptions. They were finally deciphered upon the discovery of the Rosetta stone, a single stone document which contained the same inscription in two forms of Greek, hieroglyphs.
The oldest writing in the world is Chinese. The earliest writing in China can be dated to immediately after the scattering, which happened in 2247 BC at the earliest. This demonstrates that though people forgot their knowledge of Sumerian, they did not forget the ideas of writing and quickly developed writing systems to suit their new languages.
It appears the first writing in China was symbolic marking on oracle bones used by priests to predict the future. In time, the symbols used in their religious traditions were used in art and basic literature.
The earliest characters were logographs, like hieroglyphs. Sometime during the Qin-Han period, a new set of standard characters appeared. All characters since this time were a mix of logographic and phonographic elements.
China was far and away the most powerful and influential civilization in East Asia for thousands of years, and it is no surprise that Chinese writing heavily influenced the development of writing in nearby civilizations like Japan and Korea.
Writing was introduced to Japan by the Chinese civilization around 400 BC. The Chinese system was adapted and altered to more efficiently write the Japanese language.
The Korean writing system, Hangul, was invented by Sejong the Great in 1443 during a period of Korean nationalism. Previously, Korea had used the Chinese system, but upon achieving independence, Hangul was invented to remove Chinese influence from the newly minted nation.
Indus Valley script, also known as Harappan, was developed in the third century BC in India, making it one of the oldest known writing systems. This is consistent with the account in Genesis 11, which describes the creation of new languages at 2247 at the earliest. It is possible that merchants trading in the Indian Ocean spread Harappan to Sumer, influencing the development of cuneiform there. Thousands of inscriptions have been found, using 417 different symbols.
Although linguists continue to examine the relics, Harappan has not been deciphered. Harappan civilzation may be the earliest Indo-European settlers coming from the Caucasus mountain, or it may be a civilzation which existed before these people migrated to India. If Harappans were Indo-European settlers, then it is possible the Harappan script is Indo-European and will someday be deciphered. If Harappan is the writing system of a people who were displaced or destroyed by Indo-European settlers, then the language is a dead language with no modern descendants; such a language may never be understood.
The oldest writing in the Western Hemisphere is from approximately 900 BC, and of Olmec origin. However, the writing sample that has been found from this time appears to show a fully developed alphabetical system with 28 different symbols, so it is certain that writing had been discovered more than three thousand years ago in that region.
Some of the oldest non-Egyptian writing systems in the Mediterranean are still undeciphered. Likely from the Minoan civilization, these scripts, known as Linear A and Linear B, are very similar to ancient Greek and obviously had a strong influence on the development of it.
Greek was also heavily influenced by simplified Egyptian hieroglyphs, Hebrew and Phoenician. All these writing systems developed about the same time in the Eastern Mediterranean.
By 1491 BC, Hebrew was sufficiently developed for the Ten Commandments (presumably written in Hebrew, although possibly in Egyptian hieroglyphs) to be written by God on Sinai. The earliest Hebrew inscriptions still existing date from approximately 1000 BC, shortly before the rise of the Kingdom. Hebrew was abandoned for non-religious texts during the Babylonian exile in favor of Aramaic, and remained so until Diaspora of 135 AD, when Jews began to use Hebrew more to keep in touch with their identity while among non-Jews.