[AlexanderHowl]

I believe those are culturally acquired traits for people with suburban or urban backgrounds. Children of hunter-gatherer and pastoral cultures learn to kill animals for food really early on (as early as age four from my recollection) and are taught how to defend themselves from predators (animal and human) from an early age. Children of rural families in both the developed world and developing world will learn to hunt and kill from an early age in the modern era, and I doubt that anything but the weapons would have changed for a medieval or ancient society.