We are a hierarchal species. Like other great apes, individuals in human societies find their behavior restricted by others. As societies became larger, organizations beyond the family evolved to regulate behavior. Of course, family is still a very important political asset - we need only think of family names like Kennedy and Bush to recognize this fact.

Religions have also played a major role in politics. In previous eras and still in some countries (e.g., Iran), it is difficult to separate church and state. Even in democratic governments like the US, religion still plays a major political role.

As your text notes, the economy is a major influence in selecting government officials. The costs associated with running for high political office almost guarantee that public officials will represent the large monied interests.