Good point. There must have been a literate class, at the very least, probably analogous to many an ancient civ’; the Egyptians and the Romans both relied on quasi-literacy among the general population, iow an understanding of a relatively few symbols (number system in Roman times; the Egyptians had symbols for “enter here” on the temples’ public entrances), with a fair percentage of people who could read and sometimes write.
In the Euphrates basin, regular flooding led to a need for both surveying (math) and recordkeeping (accounting, then writing) to make sure people were able to stay on their property and cultivate it. I’d be surprised if something along those lines didn’t happen along the Indus as well.
Settled agriculture is the basis for civilization, and leads to larger, healthier populations, larger families, more leisure time, and the development of other arts and industries, as well as standing armies.
About that statue of the “dancing girl”.
Her left arm. Couldn’t that be some form of armor or protective wear? What’s in her left hand?
Could she, possibly, not be “dancing” but geared up for a sport of some sort?
And, could that be proof that they were all left handed?
Heh.
Satindoll is right — and also gives an explanation for the paucity of writings — perhaps they were written on material that was even more ephemeral?