Theory number 3Many of the signs in the Proto-Elamite script are similar to Indus signs. It might be possible that there was interaction between the people who developed these two scripts. Proto-Elamite was developed on the Iranian plateau which is not far from the Indus Valley.
***Learn more about Proto-Elamite writing and see if this theory makes sense…This is a difficult one. Neither Proto-Elamite writing nor the Indus script has been deciphered yet. Thus, there might be some relation between the shapes of the signs in the different scripts. But we have no way of knowing for sure. Some of the signs just look so much alike - what a coincidence!
The languages used on the Iranian plateau and in the Indus Valley were most probably different. This would mean that even if the signs looked alike, they were probably used differently. In other words, the sound values given to each sign would be different. So, it seems unlikely that the scripts are closely related in terms of how they were used.