Before revision: The ruins of Mesoamerican city Teotihuacan This "urban revolution" – a term introduced by Childe in the 1930's – from the 4th millennium BCE, marked the beginning of the accumulation of transferable economic surpluses, which helped economies and cities develop.
After revision: The ruins of Mesoamerican city Teotihuacan This "urban revolution" — a term introduced by Childe in the 1930's — from the 4th millennium BCE, marked the beginning of the accumulation of transferable economic surpluses, which helped economies and cities develop.