Why did people in the eastern river valleys borrow little from people in other regions?

People in the eastern river valleys often borrowed little from other regions due to their geographic isolation and the self-sufficiency of their agricultural practices. The fertile land and abundant resources allowed these communities to develop unique cultures and technologies tailored to their specific environments. Additionally, limited trade routes and cultural exchange meant that innovations and ideas remained localized. This fostered a strong sense of identity and continuity within these societies.