<span>In the non-industrialized countries, marriage is the significant marker of entry into adulthood and it generally occurs earlier than marriage in the United States. In the United States, holding a full time job is more often the marker of adulthood.</span>
The first cities developed
in the region known as Mesopotamia
between 4500 and 3100 BCE. The city of Uruk, today considered the
oldest in the world, was first settled in c. 4500 BCE and walled cities
