For the Indus River Valley Society, some expert said dry up is the main reason and others said flood is the main reason. However, either of them are big effect agricultural. People cannot get enough food to survive. The other hypothesis is the Aryans migrated and aggression into Indus Valley, because a lot of Indus people keep the same customs of pre-Aryan. However, is not all of people accept this hypothesis.
Overall, I think the both of two early communities are collapse by climate change. Not only the early communities will change, but also with global warming more and more land submerged in the ocean right now. The modern people even cannot control the climate change. However, modern people have more ways to survive, because of the convenient conditions. The early community’s people cannot leave water, they have to use water to irrigation. They have no idea when climate suddenly change. Therefore, that is easy to understand why climate change is the biggest problem for them to