@Hypocrisy_Central asks some good questions that I will try to answer. ”[Is there] some deep seeded need in humans to selflessly?” I think there is, though not without a self-serving aspect. Upon hearing another child cry infants respond in a way that seems to be more concern than curiosity. It is not unusual for toddlers to seek to comfort a distressed peer. Often children will spontaneously share snacks and toys with others.
I am paraphrasing what I believe you are asking in your second question. Is the aim of what appears to be selflessness actually “a selfish need to feel liked, or to be a ‘good person’, etc.?” Dependent upon adults to insure survival, an innate fear arises when nurturing seems to be threatened, as when a significant adult becomes sad or angry, and the child will seek to ameliorate it; this behavior is evident in many domesticated animals as well. In a sense, seeking to diminish anxiety is self-serving. One might see seeking approval and acceptance from others or to be seen as a good person as selfish. However, to accomplish their intention the child would need to give approval and acceptance to those it sees as a good person.
What is “perceived to be a threat” depends upon the form that the threat takes. People whose intent is unknown are likely to be regarded as a potential threat. Should they appear to be friendly their approach will be cautiously tolerated; trade between tribes would never have happened if all strangers were attacked. When resources are limited, however, groups will muster forces to attack or defend. Each will regard themselves as “good” and the others as “evil”. Neither is either. Animal instinct for survival, which is amoral, will trump any desire for altruism they may have.