What determines the degree of 'sinfulness' the human race gets from original sin?

Continued from here.

Suppose that there is something called 'original sin' that biases humanity's choices towards evil. Why does it bias the human race to the specific amount of evil that we do? Why isn't the human race much nicer, with fewer awful events, or much worse, with more evil? What determines our sinfulness as a group affected by original sin?

The 'weight' of original sin is basically the push on the human will to make decisions in terms of game theory, and rational self-interest, rather than blindly doing the right thing.

So for example, in the prisoners dilemma, the rational thing to do is to act wrongfully (edit: meant to illustrate a principle; it's a good thing for those who commit crimes to get arrested).

From Wikipedia:

"Two suspects are arrested by the police. The police have insufficient evidence for a conviction, and, having separated both prisoners, visit each of them to offer the same deal. If one testifies (defects from the other) for the prosecution against the other and the other remains silent (cooperates with the other), the betrayer goes free and the silent accomplice receives the full 10-year sentence. If both remain silent, both prisoners are sentenced to only six months in jail for a minor charge. If each betrays the other, each receives a five-year sentence. Each prisoner must choose to betray the other or to remain silent. Each one is assured that the other would not know about the betrayal before the end of the investigation. How should the prisoners act?

...In this game, as in all game theory, the only concern of each individual player (prisoner) is maximizing his/her own payoff, without any concern for the other player's payoff. The unique equilibrium for this game is a Pareto-suboptimal solution, that is, rational choice leads the two players to both play defect, even though each player's individual reward would be greater if they both played cooperatively... Since in any situation playing defect is more beneficial than cooperating, all rational players will play defect, all things being equal."

Similarly, in the tragedy of the commons the rational thing to do is to act wrongfully. This has been proved mathematically. That is the self-interested thing.

The tragedy of the commons:

"As a means of illustrating these, [Garrett Hardin] introduces a hypothetical example of a pasture shared by local herders. The herders are assumed to wish to maximize their yield, and so will increase their herd size whenever possible. The utility of each additional animal has both a positive and negative component:

* Positive: the herder receives all of the proceeds from each additional animal.
* Negative: the pasture is slightly degraded by each additional animal.

Crucially, the division of these costs and benefits is unequal: the individual herder gains all of the advantage, but the disadvantage is shared among all herders using the pasture. Consequently, for an individual herder the rational course of action is to continue to add additional animals to his or her herd. However, since all herders reach the same rational conclusion, overgrazing and degradation of the pasture is its long-term fate. Nonetheless, the rational response for an individual remains the same at every stage, since the gain is always greater to each herder than the individual share of the distributed cost.

Because this sequence of events follows predictably from the behaviour of the individuals concerned, Hardin describes it as a "tragedy"."

So in sum, original sin 'weights' our choices in the sense that it makes game theory and rational self-interest very important in how we decide things. Original sin is the 'curse' (some would say blessing) to evaluate moral decisions based on game theoretic considerations, instead of 'blindly' doing the right thing.