Most of the ancient cultures I've read about all have similar weapons, for example Europe, The Middle East and Asia all had metal swords, the Aztec used Obsidian swords, virtually all had bows, shields and spears. Were swords and bows etc. all made in the same place once and then spread, or did different people invent them in different places all across the world? If they were invented separately, how are the designs so similar?
Not addressing "swords, maces, etc.", but with regard to bows and arrows, there have been several good threads: check out this FAQ section:
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This is an enormous question when you include multiple technologies throughout the entire world. With regard to the bow and arrow within North America please see this. I conclude in that post that the emergence of bow and arrow technology in North America is attributable to both diffusion and independent invention.