Becoming, the previous link in Dependent Origination, is not continuous; it moves from birth to birth to birth as the necessary conditions come together that foster its arising. It is useful to get a sense of the birthing experience of self and what the conditions are that bring this about. Instead of trying to catch your origin, which is a little like trying to observe the first moment after your mind wanders, get a sense of how you inflate, relative to the strength and intensity of the thoughts you have. Notice in times of relative quiet how the egoic sense of you is markedly diminished, and at times of reactivity or heightened enthusiasm, the sense of you is large and noisy. Don't explain this away by saying that "you" became noisy and self-righteous because you care about the issue. Take the personal out of the observation and just notice your relative size as a phenomenon related to the noise of your thoughts and emotions. As this increases, so does that; as this diminishes, so does that. Now contemplate this question: how does the noise of your inflation move in accordance with desire and clinging?