Indus Valley Civilization:
- Collapse: The Indus Valley Civilization went through a gradual decline and eventual collapse around 1900 BCE. The reasons for this decline are still debated, but theories include changes in the course of the Indus River, climatic changes, and potential invasions.
- Unknown Demise: The specific reasons for the decline and fall of the Indus Valley Civilization remain largely speculative due to the limited archaeological evidence available.
- Cultural Transformation: The decline led to the end of the urban phase of the civilization and a shift towards smaller settlements. There was also a change in cultural practices and material culture.
Huang He Valley Civilization:
- Conquest and Assimilation: The Huang He Valley Civilization faced external pressure from nomadic groups, particularly from the expansion of the Zhou people. Around 1046 BCE, the Zhou conquered the Shang Dynasty, which was the ruling dynasty during the later stages of the Huang He Valley Civilization.
- Cultural Continuity: Despite the change of ruling dynasties, the Zhou adopted many cultural elements from the Shang, leading to a cultural continuation.
- Political Centralization: The Zhou established a more centralized political system and feudal states. They continued the practice of ancestor worship and oracle bone divination.
In summary, the Indus Valley Civilization experienced a gradual decline and ultimate collapse, with the causes still debated. The Huang He Valley Civilization, on the other hand, faced external conquest, leading to the assimilation of the Shang culture into the Zhou Dynasty, resulting in cultural continuity and political centralization.