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 presidential system, the legislature and the executive do not have to be aligned and often work against each other. 2  Policy implementation can be much slower and more moderated, at least in the US system.
This is in contrast to a presidential system in a democracy, where the head of state often is also the head of government, and most importantly, the executive branch does not derive its democratic legitimacy from the legislature.mplementations of the parliamentary system can also differ on the manner of how the prime minister and government are appointed and as to whether the government needs the explicit approval of the parliament, rather than just the absence of its disapproval.