I write comics and one of our artists from southeast Asia informed us that she was bothered by the eye-leading from one of our pages, which follows the traditional western convention of right to left. She wants to flip the page to make right to left, more in line with manhua or manga.
This lead to a conversation with my partner about why different cultures would adopt different reading conventions, and we guessed it had to do with language, but that still left us wondering why those conventions might have come about in the first place.
Thanks!
Oh goody, this is a great question. The answer is fairly long and complicated, but I'll try to boil it down to its base components.
First off, we need to specify that there really isn't an "East vs West" split in how you write, as it can vary a lot even within the same grapholectic families. The Latin and Greek scripts, for example, are written left to right in the modern world, but Arabic is written right to left, even though all 3 writing systems come from the same Proto-Sinaitic script (which came from Semitic slaves working in Egyptian quarries who tried to imitate the alphabetic hieroglyphs of the Egyptians). Even within certain writing systems, it can vary; Modern Greek for example, is based on the standardized form of the Ionic Greek alphabet of Miletus, which was written L-R, but some older inscriptions in other Greek alphabets, including the Western varieties that gave rise to Etruscan, were written in Boustrophedon, that is, alternating left-right then right-left. Ogham script, the script of the Ancient Irish, was written bottom to top vertically, while Uyghur (and its descendants, old Mongolian and Manchu) were written vertically and left-to right to conform to Chinese writing standards. So there generally is no clear geographic pattern when it comes to adopting a writing direction.
So why do some writing systems choose LTR or RTL? The short answer: we don't really know. Writing developed so long a go that it is difficult to get a proper answer. There are a number of theories floating around, the big one that comes to mind is that directionality is influenced by medium; most people back then (and now) were right-handed, so epigraphic inscriptions required a right hand on the hammer and a left hand on the chisel, so moving RTL was the more intuitive form, but when papyrus became a popular medium in Egypt, RTL was adopted to avoid smudging with the hand. There are a bunch of criticisms regarding this theory, however, namely that of cuneiform writing (Sumerian, Old Persian) which, while also epigaphic, was written LTR. This can somewhat be accounted for because many cuneiform inscriptions (particularly those used in education in Sumerian edubba) were made on clay tablets with a stylus, not a hammer and chisel. Still, that alone does not account for why LTR was still used in incriptions like those in Behistun.