What questions remain unanswered about the Harappan language and Indo-Aryan speakers?

Significant questions remain regarding the Harappan language and the arrival of Indo-Aryan speakers in the Indian subcontinent, primarily due to a lack of definitive evidence.12

The Harappan Language

The primary challenge is that the Indus script remains undeciphered. Because there are no bilingual inscriptions to serve as a key, scholars have been unable to confirm the language family of the Indus civilization. While various theories have linked the script to Dravidian, Indo-Aryan, or other language groups, none have gained widespread agreement. Some researchers argue the script may not represent a single language at all, but rather a pictographic system used by a multilingual population.34

Indo-Aryan Speakers

The history of Indo-Aryan speakers is equally debated:
* Migration vs. Origin: While linguistic evidence generally supports the migration of Indo-Aryans from an external homeland, some scholars argue they were indigenous to the subcontinent. Definitive archaeological evidence for either migration or emigration is lacking.12
* Interaction with Harappans: It is unclear whether Indo-Aryans encountered the Harappan people or if the civilization had already declined by the time they arrived.1
* Material Culture: Even if Indo-Aryans established influence in the region, it remains unexplained why they appear to have adopted local material products while presumably retaining their own language.2