The Sumerians were the first people to migrate to Mesopotamia, they created a great civilization. Beginning around 5,500 years ago, the Sumerians built cities along the rivers in Lower Mesopotamia, specialized, cooperated, and made many advances in technology. The wheel, plow, and writing (a system which we call cuneiform) are examples of their achievements.
1 In a Parliamentary System, the head of state is usually a different person than the head of government (not in every country). 2  The HOG is often vested with more official power, but holds that position for a relatively short time.
Presidential System of Government. A presidential system is a system of government where an executive branch is led by a president who serves as both head of state and head of government. In such a system, this branch exists separately from the legislature, to which it is not responsible and which it cannot, in normal circumstances, dismiss. Curated by.