Scientists say that the Earth may be as many as six billion years old, and that human beings in their present form first appeared around 100,000 years ago in Africa. The earliest humans lived by hunting, fishing, and collecting edible roots and fruits. Only some 10,000 years ago did they learn to cultivate plants, herd animals, and make airtight pottery for storage. These discoveries transformed them from gatherers to producers, and allowed them to grow in number and to lead a settled life. People also migrated from Africa to other parts of the world, and adapted to new climates and new conditions.
Gradually, humans learned how to increase harvests through irrigation and other methods, making possible much larger populations. They came together in towns, cities, and other centres, where they erected impressive structures and where industry and commerce flourished. In time, different civilizations came into existence in various parts of the world.