People continued to speak mutually incomprehensible languages, obey different rulers and worship, but all believed in gold and silver and in gold and silver coins. Without this shared belief, global trading networks would have been impossible.
Christians and Muslims who could not agree on religious beliefs could nevertheless agree on a monetary belief, because whereas religion asks us to believe in something money asks us to believe that other people believe in something.
Money is also the apogee of human tolerance. Money is more open-minded than language, state laws, cultural codes, religious beliefs and social habits. Money is the only trust system created by humans that can bridge almost any cultural gap, and that does not discriminate on the basis of religion, gender, race, age or sexual orientation.