Civilizations flourished during the warm periods, such as the Bronze Age, the Roman era, and the medieval times, when weather conditions were relatively stable with more precipitation in the tropic and subtropical areas. Civilizations experienced decline or succumbed during the cold periods, such as 1 200 to 500 BC, 300 to 700 AD and the Little Ice Age, when weather conditions were more unstable with less precipitation in the tropical and subtropical areas.
