A field of wheat
Ever since people left Africa for West Asia, about 70,000 BC, they have probably always eaten wheat, which tastes good and is also a good source of carbohydrates. But for hundreds of thousands of years, people did not grow wheat. They just picked wheat wild, wherever it happened to grow.
Sometime around 10,000 BC, though, the area around Mesopotamia and Egypt became crowded enough, and the climate hot enough, that there was no longer enough food to go around just by picking it, and people had to begin growing it on purpose, weeding out all the plants that people couldn't eat like pine trees, and planting the ones that people could eat, like wheat.
Close up of wheat seeds
Gradually people also made the wheat easier to grow and eat, by choosing the seeds of the best plants for the next years' planting. They chose wheat with big heavy heads (the part you eat), and wheat whose berries were easy to separate from the chaff and straw (the part you don't eat).
People got to have a lot of wheat and not so much of other kinds of food as they used to. They learned different ways of cooking the wheat. Sometimes they put it in a skin or a pot with water and boiled it into porridge (like oatmeal). This was filling and easy to cook, and also it uses very little fuel to cook it.
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Other times they made bread with it. This is harder to cook and needs more
fuel, but you can carry it around and keep it better than porridge, and
it tastes better. Mostly they made flat breads, like focaccia or pita bread
or pancakes or pizza, which need less fuel to cook.
By around 1500 BC, people were growing wheat even in China. They ate porridge in China too. But in China women did not make wheat into bread. Instead, they made noodles.
To find out more about wheat, check out these books from Amazon or from your library:
Bread Comes to Life: A Garden of Wheat and a Loaf to Eat, by George Levenson (2004). From wheat to bread, lavishly illustrated, for kids.
Ancient Agriculture: From Foraging to Farming, by Michael and Mary Woods (2000). For middle schoolers, with plenty of information about how farming got started, and how it worked.