Farming did not stay the same after the first hearths. Three great changes, called agricultural revolutions, each let fewer farmers feed more people.
Key idea
The First Agricultural Revolution was the start of farming itself, about 10,000 to 12,000 years ago. The Second, beginning in Britain in the 1700s, brought new crop rotations, new tools and, later, machines and fertilizers. The Green Revolution (1940s-1970s) spread high-yield seeds, chemical fertilizer and irrigation in Asia and Latin America.
| Revolution | When and where | What changed | What followed |
|---|---|---|---|
| First | From about 10,000 BC, in several hearths | Planting crops and raising animals | Settled villages, then cities |
| Second | Britain from the 1700s, then Europe and North America | The Norfolk four-course rotation (wheat, turnips, barley, clover); Jethro Tull's seed drill (1701); enclosure of fields; selective breeding; later tractors and fertilizers | Food for growing industrial cities; fewer farm workers |
| Green Revolution | 1940s-1970s, Mexico, India, Pakistan, the Philippines and more | High-yield wheat and rice (such as the rice IR8, 1966), more fertilizer, more irrigation | Much larger harvests; debates about cost and environment |
Why it works
Each revolution raised the food grown per worker or per acre. Clover adds nitrogen to soil, so the Norfolk rotation removed the need to leave fields empty (fallow). Short-stemmed Green Revolution wheat and rice could take more fertilizer without falling over, so yields rose. More food per farmer freed people for other work, which helped industry and cities grow. That link ties this topic to The Spread of Industry.
Worked example: Why short stems?
Green Revolution wheat and rice were bred to be shorter. Why did that matter?
- Fertilizer makes plants grow heavy heads of grain.
- Tall plants with heavy heads fall over (lodge), and the grain is lost.
- Short, sturdy stems hold the heavy heads up.
Answer: They could use more fertilizer and carry bigger harvests without falling over.
Worked example: Put them in order
Order these: high-yield rice IR8; the seed drill; the first planted barley.
- First planted barley: the First Agricultural Revolution, about 10,000 BC.
- The seed drill: 1701, the Second.
- IR8 rice: 1966, the Green Revolution.
Answer: Barley, seed drill, IR8.
Common mistake
Thinking the Green Revolution meant organic farming. It meant new high-yield varieties with more fertilizer and water; it raised harvests and also raised debates about cost and environment. Supporters point to the famines it helped avoid; critics point to water use, fertilizer runoff and costs for small farmers. Both sets of facts are part of the record.