During eary nomadic period, people used to live in natural caves. After they learn to cultivate crops, they started building houses with woods and bushes. Then people learn to construct houses with mud and wooden logs. Later these people improvised the mud into mud bricks. These mud bricks were used to constructed their houses. Then, they learn to manufacture dry clay bricks. These clay bricks were used to construct houses. Clay bricks were better than mud bricks.