Economics (trade)

They depended heavily on trade.
 * They traded a lot with Mesopotamia

Source: https://www.khanacademy.org/humanities/world-history/world-history-beginnings/ancient-india/a/the-indus-river-valley-civilizations
 * Gave lots of seals to Mesopotamia

They were very advanced in trading with Mesopotamia. The IRV loved trading seals as well.