You would have to put a baby human in the wild and see if it grows to kill. Otherwise, your instinct to not kill might be a result of your learned behavior.
During my vegan trial, I asked my mother if I ever spit out meat when I was a kid, and she said "no, you loved it. So did your brother and sister." In fact, I called steak "candy".
I also got extremely irritable and angry when I went without meat for a long time, which to me seems like an instinct to kill. If I felt like that in the wild with no vegetation, I would strangle an animal to death if I had to.