"But really, they did it because every human being has a basic instict to help each other out. It may not seem that way sometimes, but it's true." From Andy Weir's The Martian
I love that quote but hate the word 'instinct.' I had a history professor who at times seemed to teach in a manner similar to that of Colonel DuBois from Starship Troopers. He had a personal vendetta against the misuse of the word 'instinct' as applied to humans. By definition, an instinct is 'an innate, typically fixed pattern of behavior in animals in response to certain stimuli.' He offered $100 cash prize to anyone who could find a human behavior that met those criteria. Lots of people tried the first day, fewer people the second, and by the end of the third week the class had pretty much conceded that humans have no instincts. We have reflexes, we have conditioned behavioral patterns, but nothing complex that doesn't have to be taught.
The key word there is innate. Behavioral responses to stimuli in humans has to be taught, without exception. That is, for anything that actually goes to the brain. Your hand pulls away from a hot stove before your brain realizes it is registering pain. Reflex, not instinct.