Also it seems a bit odd they were able to make massive embossed carvings (small ones aren’t easy let alone massive ones) with heavy fertility themes. It is very impressive of anyone of the period to have made such things however to date it seems they were buried the civilization that created them. There may have been some culture here but these places seem more like part of a larger nomadic tribal network of campuses. Maybe each spot had a purpose, they could have head some heave tents like similar to a yurt. There are extensive well known cave systems in many places in the region. They may have sought refuge in the cave systems during severe weather.
I don’t envy evolutionary linguist they are often left to fill in complexities historical framing of events along with understanding how language flowed via trade, missionaries, commissioning, and conscriptions. How can you gage the impact on a mind of an human living 2000 years ago when they hear a inciting story by another gifted with a well crafted bardic tale. How often could this spread language or gods against entrenched beliefs?
Artistic motifs seem to be further evidence. There are also similarities between their scripts and scripts found in west Africa (likely ancient trading partners of Indus valley). The linkage is also found in the preservation in their religious ideals of Templars’, Eastern Orthodox, Coptics, Ethiopian Orthodox Tewahedo, and Rosicrucianism among others.
Further evidence is found in the high quality pottery which has many more implications outside a vessel for carrying liquids and foods (more on that later). During the Uruk period in Sumer there was a rise of artwork showing gods in the form of bird men carrying a cauldron and pine cone. This is very important to feeding people; syrup from pine nuts is highly nutritious (medicinal) but also the cauldron allows for rice cooking and green pine cones. This is important because iron ore (goods) were a major export of pre-India civilizations. This smelting capacity also made them prolific seekers of tin and copper.
At the same time irrigation systems were built. This is important for two reasons. First, this brought rice farming, which also came from pre-India civilizations. Rice farming and Pine cone harvesting are also part of high quality pottery. This is due to the gluten in rice water and rice flower, rice bran being key additives in turning natural clay into a quality clay. The next additive that is noteworthy is also tied to the pine cones. Pine tree tar / pitch seems to be a crucial part of carbon nano tube formation (evidence here: Biological effects of carbon nanotubes generated in forest wildfire ecosystems rich in resinous trees on native plants - PMC). It appears that resin or tars and terpenes found in many trees in the pine family hold this capacity. Sir Lankan pottery has been found to have nano carbon tubes as far back as 2600 years ago. (Discovery of carbon nanotubes in sixth century BC potteries from Keeladi, India - PMC).