1 The writing represents speech notion
Speech and writing originated independently of each other. Human speech probably appeared long time before writing. Earliest writings developed from drawings. They were of visual origin, as pictographs, ideograms. As time went by, writings were spatially arranged sequentially in lines, corresponding to the sequential property of speech in time domain. As writing systems evolved in the alphabetic direction, writings and speech associated with each other tighter and tighter, continuing to present day. The alphabets lost pictographic property. As alphabetic systems have replaced their pictographic  predecessors and gained prevalence, it seems natural to conclude that the evolution of writing systems is to better represent language sounds. This conclusion is elegant, intuitive, reasonable and basing on facts and researches. It certainly cannot explain some cases, for instance, the Chinese didn’t evolve into alphabet. However, the Chinese characters are blamed to be too complex to represent speech. The modern Chinese writing is more tightly associated with spoken Chinese than ancient Chinese writing does. Moreover, characters have been simplified in mainland China. Chinese writing looks like taking a small step towards representing speech. Little doubts have been casted on this conclusion, although many scholars consider writing as more than simply representing speech. Representing speech seems a destined direction. Let’s be a little skeptical on this natural conclusion.
Without rigorous proof, this conclusion is taken for granted by man due to its intuitiveness and accord to most facts and history of alphabets. Let me now ask some basic questions. Why alphabets better represent sounds than pictographs do? How to determine if a script is good at representing sounds? Are some alphabets better in representing sounds than other alphabets are? Should evolution be attributed to the spoken form, written form or the representing itself? These simple questions are not easy to answer. Why not attribute the evolution of writing to the visual form, then? That can certainly have more clarity and become simple as writing itself is visual creature. Why people still stick to the ‘represent speech’ notion then? Following are some possible reasons. Speech and writing both changed a lot over time. They associated with each other tighter and tighter and are considered same thing – language. Speech is considered primary in language, which is by far meant spoken language. Speech is associated with human nature, while writing is considered an artifact. There are two points. One is they associate with each other. The other is speech is primary. The latter is itself a profound, although taken for granted. Here we take neutral position and won’t try to approve nor reject it. As we have said, speech and writing has independent origins. The link between them is not preexisting. They are set up after longtime use. The resultant connection between writing and speech shouldn’t be taken as the cause for the writing to evolve. Rather, the characteristics of writing should be analyzed to explain how it evolves visually. Then, the speech-writing association’s influence on writing’s evolution should be addressed.
2 Visual evolution of writing
Evolution of writing is reflected in its visual characteristics. We can easily see the salient visual distinction between alphabets and pictographs. Alphabet is a standardized set of letters. They usually comprise tens of letters, and are derived from complex pictographic scripts. Pictographs are complex and huge in amount. It is understandable to think that they have not evolved visually. If evolved visually, why becoming simpler instead of more complex? If writing is taken as visual art, it should evolve towards greater complexity. However, writing is a means of communication, representing and recording knowledge. The clarity, convenience, efficiency and suitability for reading thus become main concern. At the beginning, drawings were to depict something directly, as pictures. They were arranged usually in lines to represent meaning continuously. Apparently, the complex pictographs are not easy to recognize, lowering reading accuracy. It affects the reading fluency since more time is spent fixating at one pictograph before moving to the next. Complex symbols are discarded or simplified to facilitate linear reading. Some symbols had simpler and clearer visual pattern and were more frequently used. Long time passed, only a set of symbols are left and standardized. We call them alphabets. The reduction in number, simplification and standardization facilitate visual manipulation and memorization, leading the alphabets to supersede pictographs. Alphabetic writing is more suitable for reading than pictographic systems. We use the word ‘legibility’ to denote the concept ‘fit for reading’, which we think is the central in evolution.
How legibility takes effect? What is the mechanism, then? In the present world, texts explode. Through internet, one can easily find texts of any subject. The scope of the written world is virtually indefinite. Nonetheless, text still comprises basic individual symbols. Analysis can be done on the symbols and sequence of symbols. By simply analyzing the symbols, we are not overwhelmed by the explosion. These symbols are read and written by human. They have effect on humans via the eyes and brain. Legibility principle originates during reading, and then operates in thinking and writing while visual info is stored and processed in the brain. Although legible symbols can be arranged well and read easier, the visual patterns themselves are not the reason for reading. People read because the reading material reflects real world which is of the reader’s interest. Reading material is estekhdamkhabar t existent beforehand. They have to learn and use existing system regardless of its legibility and tend to read the symbols they are familiar  with. However, Texts of different degrees of legibility have different effects. Legible writing is easily read, memorized, processed by brain and written out. Legible writing impresses the eyes deeper and operates in the brain more effectively and strongly. More writings of greater legibility are read and produced than those with less legibility. After processing by the brain, the text written out has the tendency of being better patterned than those that are read. That is to say, legible writings have greater power to stimulate one to write. As a result, the writings produced later tend to be more legible than the earlier, changing the appearance of the writing system. Legibility is individual-dependent. Individual’s writing changes are not at the same pace. Change of a writing system is a result of changes made by all individuals’ written works. The appearance of post-change system usually does not differ completely from pre-change system. This evolution is a long time process and might become noticeable after generations.
Legibility principle operates starting from individual symbols, then throughout entire writing system. The recognizability of symbol/word forms, inter-differentiability of symbols, and inter-differentiability of words are the basis of a script’s legibility. Symbols/words are elementary. The strength of a writing system is usually judged on its entirety  – its all written works, the area and people it covers, all knowledge it represents etc. The dominant system is not necessarily the most legible. But legibility will exhibit its power as more-legible writing system grows faster. Individual symbols/words are building units of whole system and, basically determine how the whole system looks like and the potential it can expand. Legible symbols/words can be organized better and expand further. Legible system possesses more written works or has the potential to be such. It can grow bigger and thus represent more knowledge, leading to its success. Symbols form words, sentences and eventually a whole system. Rules/grammar develops for word formation and arranging words together. There are also recommended ways of formatting and writing paragraphs, thesis and book, but they haven’t become rules. These rules and recommendations imply the characteristics of larger linguistic units, facilitating reading and expanding legibility from symbol level to phrase, sentence levels and throughout the entire system. As time goes on, more-legible system overpowers/replaces less-legible system.