First: Neolithic, hearths: Fertile Crescent, Indus River Valley, SE Asia, Central America, 8000-10,000 BCE, domestication of plants & animals, Second: Industrial, hearth: western Europe, late 1700s, better diets; longer life expectancies; more people available to work in factories, Third: Green, 1950s, high yield seeds first used in Mexico (wheat, corn, rice); increased use of chemicals; mechanized farming, environmental impacts include pollution & soil salinization,

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