Yeah, I would compare the wordly definition of a genetic disposition, to a Fallen spiritual disposition; since we all are discussing the Spiritual nature of things here. Just as a genetic disposition can only be cured by affecting the genetics, a spiritual disposition can only be cured by affecting the spirit. Let me cut to the chase; you know why I'm investigating this, to use it to show that Regeneration precedes the Will (we already agree that Efficacious Grace precedes the Will). I'm trying to find out if Enmity ceases because our Nature is Born Again...Okay, I understand.But I don't think "genetic" is a very good term, because, at least to me, it suggests a physical essence of sin. It is not!
What if we looked at it from a relational/positional perspective. The earth is the perfect place for life because of its relative position to the Sun. Life, as we know it, is not possible on Venus (too hot) or Mars (too cold). Relationships are similar, but not in a spatial sense. Children are naturally more susceptible to faith if they are raised in a Christian environment and tend to find Christ earlier and stay faithful longer per Proverbs 22:6. But the longer one is not exposed to such teaching and/or is raised in an ungodly environment, the less likely they are to believe. Statistics show that the largest part of believers (85%) became such between the ages of 4-14.
My point is, that God is "not very far from any one of us" (Acts 17:27), and there is a definite relationship with age and proximity to the gospel and Biblical truth. The "enmity" factor is not as prevalent in those younger and exposed to the gospel, and it grows significantly stronger the older you get and thus is more difficult to overcome the power of sin when the gospel is presented.
I would think that if there is a static principle that enmity is a set factor that acts the same at age 4 as it does at age 90, then the number of 10 year olds becoming believers and 60 year olds would be more similar. Indeed, there is a decided advantage if one is exposed more amply and earlier in life than if not if one is to become a committed believer. The "genetic" approach would not seem to predict what we see in real life. Enmity with God is something that gains strength and prominence in direct relationship to the amount of exposure to the teachings of scripture at an early age, suggesting that nurture as well as nature are pertinent and serve to mitigate the severity and power of "enmity" against God and resistance to the gospel. This, I think, demonstrates that prevenient gracious movement and activity of God that clearly shows that the effects of the sinful nature are not as strong in our early years as it is in layer years, and the experience in later years is strongly affected by consistent exposure to biblical teachings in the early years.