The 6,000 years of human civilization history can be divided into three eras,
each with its own obvious technical symbol. Egyptian civilization was the peak
of the first era, with the invention of iron, which caused a phasing-out of
expensive bronze productions, as the symbol. During that time, agricultural
productivity was greatly promoted by the great use of iron. At the same time,
iron weapons also played important roles in the military domain, which greatly
improved soldiers' ability in attacking and defending.
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Papermaking
