From the point of view of neurology, as soon as the baby begins to acquire motor skills and focus their eyes, their brain begins to trim. There are neural connections that cut themselves off. In that cutting off, we begin to bring our attention into this world; to be able to perceive things as separate and distinguish shapes, heights, duration, space, color. Without that trimming, everything that the organism can perceive would be perceived and nothing will be distinguished. So, there is a trimming that happens there, and part of that trimming of our neural system is what culture does with language.
Then, over that language, many things are programmed: like belief systems, like agreements of what is good and what is bad, what is acceptable and what is not. And then over that series of values we build identities: democrat, republican, Argentinian, Mexican. From those we define our personal identity: “This is me,” “That’s not my family,” “I am not like that,” “I am like this.” But we don’t realize the layers of soil that we use to build that sense of self.