perhaps the word you are searching is egotism @krnel
Thus, selfishness is not a mere "myth" in itself, it is one quality in a dualistic conceptual framework, where the imagined unreal absolute of "selgfhsness" is on one side of a "myth" of imagination, and the 100% absolute pure unreality on the other side is the "myth" of altruism. The reality exists in the middle.
This is why I use "selfishsly atruistic" or "altruistically selfish" as a term.
Society has hijacked a very basic premise of nature. This is why it is so confusing to us
Do you say that because I used the word ego, and what I was saying somehow no longer applies to selfishness because you think it refers to egotism and not selfishness? I was describing what you are saying in other terminology to more clearly define how selfishness is not truly a myth. An ego-"I", self, is required for self-ish behavior that disregards others and their concerns. It seems you are not understanding, and think that egotism is not compatible with selfishness, when they have synonymous definitions and can be used interchangeably. Using one does not remove the other from applicability, because they are essentially the same.
e•go•tism
http://www.thesaurus.com/browse/egotism
http://www.thesaurus.com/browse/selfish
Just because it has been used as such in the language @krnel it doesn't mean it is so. This is why I wrote the article. You are using societal conformity as an argument.
You might also need to search better into the words themselves. Your reference is oversimplified.
It seems you want to keep separating the two and not understand. If "ego is a person’s sense of identity" and "selfishness means to act in your own interest", then understanding how one develops from the other is important. The sense of self, self-construct, self-image, self-view is directly tied to how we view ourselves in reference to reality, which is a worldview, perception of reality, in which others exist and are part of our social cooperative way of living. They are both linked, and you are trying to keep them separate as to deny the validity of what I am saying.
Ego = I = self. Simple, yes. It is the sense of self, everything I have suggested. And it relates to being self-ish. From self, to selfish, requires ego-I. Ego is inextricably linked to the concept of being selfish. You tried to invalidate the connection. Synonyms are valid, they are metaphorical (as X as Y, X like Y) correspondences. Maybe you need to go look at your etymological understanding instead of projecting that deficiency onto me. Peace.