Many important principles of American government can be traced as far back as 2500 years ago, originating in the civilizations of the ancient Mediterranean civilizations of Greece and Rome. To answer your question I will respond to the Greek influence. The word democracy is derived from the Greek word demos meaning the people and kratos meaning rule. Translated is defined as a system of government where by political power rests with the people. Having said that it must be understood that this political philosophy had nothing to do with equality.
The idea of democracy began in Athens as an 'oligarchy' where a few people held political power for the majority. In ancient Greece the oligarchy was made up of a council of the wealthiest male citizens. Women were not considered citizens, therefore were not permitted to participate in the political process. However, the demos-kratos that developed in Athens did plant the seeds of the democracy we understand today in the United States.