Inequality clearly increased with the arrival of metals, which partly allowed, from 3000 to 2000BC onward, the appearance and development of a social organisation based on the emergence of elites. Once the initial power structure was established, it attempted to perpetuate itself dynastically by increasing social control and building up familial alliances with other chiefs. 

อ่านต่อเพิ่มเติม โรงเรียนบ้านมะขามเอน 

สาระสำคัญ  เคมี