Sumerians made bricks from clay and straw because

Sumerians made bricks from clay and straw because  it is one of their major industry of that time. Sumerians has abundant materials  of clay which gives large part of their economy. Bricks was mixed sand, water,mud,straw and it was dried to sun or fuel for firing.

in 476 c.e. romulus, the last of the roman emperors in the west, was overthrown by the germanic leader odoacer, who became the first barbarian to rule in rome. the order that the roman empire had brought to western europe for 1000 years was no more.

the mongolian invasion of china and central asia resulted in a disruption of the silk road as the chinese garrisons lost support from the chinese kingdoms which fell under the mongols. however, as the mongols established a formal dynasty in china, the successors of genghis khan restored the garrisons along the silk road allowing the safe travel caravans again.