certainly Adam and Eve's ability to disobey and eat from a tree they were told not to eat from was a cause of their sin - but what did eating actually do.

The word translated "evil" in the Tree of the Knowledge of Good and Evil means, at least in one of its definitions, "the breaking into smaller pieces". The first actions after eating can be taken a couple of ways:

• you can make them becoming aware of their nakedness as a sexual issue; or
• you can understand it as an issue of self-focus.

When they make something to cover themselves they do not do it for each other, they do it for themselves. Certainly, God knew they had eaten of the tree because they were now ashamed of their nakedness - so that sudden awareness of self and desire to hide from the rest of the community was not His creative intent.

I think the ongoing sin after the garden is our separation from God and each other - our individualism and desire to serve ourselves at the expense of others. Certainly, Christ made it clear that obedience of His commands showed that we loved Him and God - but nearly universally the commands we were to obey had to do with taking our eyes of ourselves and taking ourselves out of the center of our universe by focusing on loving God and loving people. Time after time it is about diminishing ourselves (becoming last to become first) or becoming poor in spirit, etc. It was about letting go of what was important to us to look at what is important to God and other people. And, it is always about the heart behind the action and not necessarily the action itself.

Nearly universally around here from the most theologically conservative, Biblically-focused (moi) to the most theologically liberal we agree that sin is not about the action or the disobedience - it is about the separation from God that causes. The repentance necessary is not necessarily "paying the price" for our disobedience - but turning back to God. The sin was taking our eyes off God and, usually, putting them on ourselves. The solution is putting them back on God. You can frame that as obedience and disobedience - but that horribly lacks in nuance and understanding of the real issue. It, as someone says elsewhere, leads to "works righteousness" - trying to "do" the right thing rather than "be" the right person in right relationship with God.

When Paul talks about "sin nature" he talks about it as being an internal struggle between the desires of his own self, and the desires of God:

Romans 7:14 For we know that the law is spiritual – but I am unspiritual, sold into slavery to sin. 15 For I don’t understand what I am doing. For I do not do what I want – instead, I do what I hate. 16 But if I do what I don’t want, I agree that the law is good. 17 But now it is no longer me doing it, but sin that lives in me. 18 For I know that nothing good lives in me, that is, in my flesh. For I want to do the good, but I cannot do it. 19 For I do not do the good I want, but I do the very evil I do not want! 20 Now if I do what I do not want, it is no longer me doing it but sin that lives in me. 21 So, I find the law that when I want to do good, evil is present with me. 22 For I delight in the law of God in my inner being. 23 But I see a different law in my members waging war against the law of my mind and making me captive to the law of sin that is in my members. 24 Wretched man that I am! Who will rescue me from this body of death? 25 Thanks be to God through Jesus Christ our Lord! So then, I myself serve the law of God with my mind, but with my flesh I serve the law of sin.

Again, someone can try to make this something about sex; but Paul used "flesh" and "sin nature" almost interchangably. This is about serving ourselves and our own needs rather than the law of God - which is again those things Christ told us to obey: take our eyes off our self and place it on God and other people.

The "Original" sin, and our continuing sin, is about doing what pleases us at the expense of God and others. The disobedience only comes in because the law of God highlights our love of self.