Where does the instinct to help others come from?

Out of the Silent Planet

At the very beginning of the book, one of the first things that stuck out to me was how Ransom almost instinctively agreed to help the woman find her son who was coming home late from work. Even though Ransom had his own problems to sort out, his first thought (even before thinking about his own problems) were that he should help this woman. In the following scene, when Ransom is looking around for the woman’s son, there are several times he seems to regret having offered the woman assistance.

“The last thing Ransom wanted was an adventure, but conviction that he ought to investigate the matter was already growing upon him…”

Even though Ransom seems almost resentful of his instinctual desire to help others, it is clear that it is part of him. Where does this instinctual desire come from? Many people share this same feeling of obligation in regard to helping others and I am just curious about where this feelings come from. Is it because this instinct was placed inside of us or is it because our environment growing up has influenced to respond to situations like this by offering assistance. This section also made me think about the idea that we often write things that have deeper meanings that we are not at first aware of (the idea that when we write we subconsciously write parts of ourselves into what we are creating). I wonder if Lewis shared this instinct with Ransom---the instinct that he should should help others, even when he does not feel like it.