Dude, those bullhorn guards really make for cooool weapons!
About ironwork in New Guinea: first, it's great to see that reference. Thanks Tim! Second, the Vogelkop Peninsula is the extreme eastern end of New Guinea, and they've been trading with Indonesia for centuries. That's where the bird of paradise skins were traded, for one thing.
The rest of that big, big island, especially the interior, was largely cut off from trade with the outside world, and that's why they used stone tools.
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