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原始社会人类使用的工具主要是石器和木器。在大约4000年前,人们偶然发现,某些坚硬的石头经过火烧后可以炼出金属物质。这是一个划时代的变化,青铜器的出现大大提升了农业
Primitive society human use of tools are mainly stone and wood. Some 4000 years ago, it was discovered by chance that certain hard stones could be pyrolyzed to produce metallic materials. This is a landmark change, the emergence of bronze greatly enhance the agriculture