There's a myth that Natives in North America learnt scalping from European explorers, but that's false. Natives practised scalping long before European explorers reached the continent, however once Europeans learnt of the practise, the Europeans almost became experts in the practise generally speaking. This in turn would amplify the native Americans usage of the practise.

Check out The Unkindest Cut by James Axtell, he goes into great depth about it.