During
ancient times, humans did not live in houses. Instead, they lived in caves.
Then, humans learned to use animal skins, sticks, leaves and soil to build
simple huts and tents. Gradually, humans stared to use stronger materials such
as wood, rocks, cement, concrete and iron to build houses.
In olden
days, humans used tree trunks to build bridges. Then, wood and planks were used
to build stronger bridges. In 1779, Abraham Darby built the first iron bridges.
Nowadays, bridges are mostly built from concrete that is supported by strong
steel structures.
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