The Senate of Rome came into being with the Republic in 509 B.C, after the last Etruscan King was overthrown. Originally comprised of 300 members, the Senate became the seat of power in the Roman Republic: introducing laws, nominating magistrates from its own members, and influencing clients to act on their behalf.
At its heart, the Senate was always a nepotistic club, consisting of family members succeeding family members over the generations. In the century between 230 B.C. and 130 B.C, for example, two hundred consuls were elected. Of those, 159 came from 26 families and 99 came from only 10 families. Despite its narrow ruling class composition, the Senate was an effective governing body for centuries.
As the Roman territory expanded in the late republican years, the Senate became less effective, because it could not adapt to the changing requirements for government. Ultimately, its poor judgment and the rising power of the people led to the fall of the Republic and the rise of the Empire. The people rose partly because the generals began to pay the troops directly, causing a transformation from a citizen army to a professional army. Troops loyal to a power hungry commander could overthrow a government, as they did for Julius Caesar.
The United States Senate was modeled after the Roman Senate – a body of elder statesmen design to act as a brake against the whims of the people, whose interests were expressed in House of Representatives. The original plan called for senators to be elected in the same way as representatives, but this was voted down by “small” states who feared states with the largest territories could control them. The framers also feared a repeat of what happened to the Romans -- too much power by the people resulting in demagoguery -- so they put in place a system where Senators were elected by the states rather than the people.
What can we say about the Senate today? Certainly it is made up of rich men (40 millionaires by last count), but is it still an effective body? The Roman Senate was corrupted by bribes. The American Senate is corrupted by lobbyists. What this means for the future no one can say, but the Roman Republic was strong enough to survive for 450 years, while our Republic has endured for less than half that span.