Indis Valley Seals - A Black Whole of History?

i expect that i may eventually talk in my ris doorways and time about the great archaeological discoveries. I may talk about the uncovering of the indus valley civilization, which is possibly the most momentous archaeological discovery ever made. It also had very little or no writing. We don't know what language they spoke, or if it was even a single language or not. Some argue that they are pictographic or logo graphic, that the symbols represent words. But even if so, does that count as language or not? It's all up in the air.