Evil comes from Satan who at one time was faithful to God. Enough proof. He had other plans and he wanted to be God in controling things.
The missionaries go into a native villiage that no other human has ever been, they come across these people, women without tops and men showing their buttocks and eveyone just about naked, dancing around a fire, mothers openly breast feeding their children, and men stretching their penis's as it is their fashion, they have big lips with plates in them.
The missionaries say, this is evil, they are nearly naked and look at the disgusting things they do to their personal parts, they need to learn about morals, we will introduce them to sin. After being introduced to sin, they wear clothing that covers their intire bodies, they stip the the penis lengthening and lip plates tatooing dancing around the fire and all the other terrilbe satanic sinful things they were doing against the missionaries God.
These people are intoroduced to things they have never known. The first murder in this tribe accured a few months after the introduction of sin.