Ancient civilizations in China, India, and Southeast Asia developed along river valleys where conditions supported agriculture. Key features of civilizations included systems of government, distinct occupations, writing, religion, and scientific/artistic achievements. The Indus civilization declined around 1500 BC possibly due to floods, disease, or invasion while the Shang dynasty in China fell in 1150 BC after the last king was killed during an invasion, beginning China's Warring States period.