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.
A parliamentary republic or parliamentary constitutional republic is a form of a republic which operates under a parliamentary system of government.n contrast to a presidential republic and the semi-presidential system, the head of state usually does not have broad executive powers as an executive president would, because much of those powers have been granted to a head of government (usually called a prime minister).