The simple answer is that we read from left to right because we write from left to right. And why do we write from left to right? Written English is derived from Latin (written from left to right) which was derived from Greek (also written from left to right). Okay, so why did the Greeks write from left to right? There are lots of theories, but no one knows for sure.
The first Western written words were probably written in mud more than 5,000 years ago. They haven’t survived. However, there was also writing in stone thousands of years ago (the Ten Commandments, for example). For a chiseler chipping away, the writing was probably from right to left. A right-handed chiseler could chip with his right hand and brush away debris with his left hand without putting down his chisel. Semitic-derived languages such as Hebrew, Arabic, Farsi, Yiddish and Urdu continued in a right to left pattern, and still do, except for the writing of numbers, which are usually written left to right.
Another way of writing, called boustrophedon, meaning “as the bull walks,” alternated the direction of the writing. One line would go from left to right but the next would go from right to left. This kind of writing can be found in some ancient religious texts. It was used in the oldest Egyptian, Etruscan, Greek and Latin writings.
Cuneiform writing went from left to right, perhaps so right-handed scribes would not smudge their work in clay with the heel of their hands. For the same reason, languages that were written with brushes (Chinese and Japanese) might have been written from top to bottom. The painter/scribe held his brush differently from the way we hold a pen, but to avoid smudges, he went down the page, giving the writing at the top time to dry before a second column was started.
That explains the top to bottom format, but not the right to left format.
As for the Greeks, they wrote on papyrus, a precursor to paper. With most people being right-handed, a Greek writer could see what he had written without his hand smudging it or covering it if he wrote from left to right. We inherited that tradition in the English language. Until ball point pens came along, our ancestors wrote with fountain pens and before that with quill pens, both of which required blotting to absorb the excess ink and to prevent smudging. Smudging was common in the past, but has become a problem we rarely have any more.
Perhaps the reason we write—and read—from left to right is as simple as to reduce smudging.
Whatever the reason, it is important to acclimate your child to reading from left to right. More on how to do that in a later blog.