Which peoples before & contemporary with the Chinese, could've discovered gunpowder?

Were they overrun by the Inca or could they feasibly continue their work under the Tawantinsuyu?
They were annexed peacefully and retained most of their freedoms and rights, including the right to continue practizing their faith and most positions of authority (The Chimu Lord was carried to Cajamarca alongside Atahualpa, for example). They could have very well continued to experiment under Incan rule.
 
They were annexed peacefully and retained most of their freedoms and rights, including the right to continue practizing their faith and most positions of authority (The Chimu Lord was carried to Cajamarca alongside Atahualpa, for example). They could have very well continued to experiment under Incan rule.

Excellent, this suits my purposes greatly.
 
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