I believe our primitive minds conceived of the idea of evil. But evil is really subjective to the viewer. Like time is relative to the observer. Evil is just another word for living. A lion eating a cow. Some might say the lion is evil. Or a teenager doing drugs, some might say he is evil or doing evil, but if that led him to a path of beterment for his mind, spirit and soul then its good. Evil is not inherent, it's just a really simple bad way of looking at human behavior without really studying the causes and effects. Basically evil is a judgement of an the moment of "now". Without looking at the whole of all moments that led to and from the moment judged evil. And at any given time the def of evil can drastically change. At one point certain religious sects were considered evil and anti establishment, now they are the establishment, and in my opinion evil. Can humans be jerks to each other. Yes. Are humans born with a need to be "evil" to each other. No, it takes alot to create a person to be truly evil. And evil people or so called ones can have moments of enlightenment.
For instance that evil serial killer Jeffrey Dahmer actually found G-d and was interested in finding forgiveness from Jesus.
If we loo at the def from classical theology we can say that true evil does not repent, it continually rebels against all that is holy and good.
To be truly evil one would need to seek to harm themselves and others and the universe without the slightest bit of guilt taking hold. In which case, humans cannot be inherently evil since most people are self serving which is good. Even if they go about it in an evil way.
I apologize if this seems confusing some evil smoke in the air has rearranged my neurons for a moment. But thats my opinion. And I'm probably wrong, cause as a human we all have some crazy notions on what is good, bad, awesome, and sexy.