system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Most languages are written left-to-right, which seems to make sense since the majority of people are right handed. Why are some languages, like Arabic or Chinese, written right-to-left and/or vertically?
gpt
Some of the most ancient written languages read right to left because they were originally carved with something like a hammer and chisel. You normally hold a chisel in your left hand and swing the hammer with your right. This created a natural right to left motion; also, if your chisel slipped it wouldn't gouge through figures you had already carved. 

Later writing was done by making impressions in a clay tablet with different shaped reeds. Top to bottom or left to right made more sense because your hand wasn't hiding what you had just written. Even later, when pen and ink were being used, left to right was favoured because it ensured that you wouldn't be dragging your hand through wet ink.