All humans have inherited a mechanism in their brains that assesses if a given creature or object is a member of the Me and Mine group or the Them and Theirs (Other) group. This is an old survival technique that is totally obsolete in our modern lives. As I have explained in my post about macroorganisms, another important human survival skill is building strong communities in which survival depends on the successful cooperation of the members of the group. This group is what we usually define as Me and Mine. We define everything else as Them and Theirs.
When resources are scarce and populations isolated, it is very useful to be able to define an Other group, because the empathy and compassion that are expected within a macroorganism are not required in dealings with the Other. You are free to prioritize the survival of You and Yours even at the expense of Them and Theirs.
But this mechanism is obsolete for many living in a world of abundance and connectivity. Selfishness is mostly unnecessary. Prosocial choices tend to reap the most rewarding benefits (such as a sense of fulfillment and loving relationships vs. the money and power than can often come as benefits of selfishness). Almost all of the human macroorganisms have merged into one global macroorganism. Our survival is now dependent on the successful cooperation of all humans.
Some people draw the line between themselves and the Other based on biological ties. Bloodlines are still massively important in many cultures. But even if you believe in Adam and Eve, you have to admit that there is One Human Family. There is no human that is not at least distantly related to every single other human. The difference genetically between any two humans is extremely small. (There is also One Living Family, but if I talk about that I’ll lose the Adam and Eve people).
There is no Other. It’s an illusion we created to justify selfish and antisocial behaviors. Cooperation is more effective. (Just ask the Cambrian Explosion).