everybody has the instinct to kill.
but "could we?" honestly, not meaning to be sexist or anything, but some men would probably be more willing to kill than some women
that being said, i guess you can also say some women may probably be more inclined to kill than some men..
it's all about the psychology of the individual. (there, i just negated the entire sexism element i previously attempted to remove by negating the sexism element)
if two people were stuck in a room with moving walls, about to be crushed, and for some reason only one was supposed to get out alive (say it's some freaky B-grade horror movie), you'd do whatever the hell you can to be the one to escape. the level of mental damage after doing so, varies from person to person - person A might never get over it, while person B would probably rejoice at his/her successful survival, or see it as something that had to be done, and think nothing of it.
reflecting on myself, i don't know if i'd be able to do it. then again, you only find out what you're capable of when you're in the heat of the moment. on the surface we try to be good, civilised people, but if you take our houses and our supermarkets and our money away, it's all about instinctive survival.
no? well, i tried.