Check this fascinating feature on human evolution on BBC. One part of the report struck me:
Comparative studies between humans and chimps show that while both will cooperate, humans will always help more. Children seem to be innate helpers. They act selflessly before social norms set in. Studies have shown that they will spontaneously open doors for adults and pick up “accidentally” dropped items. They will even stop playing to help. Their sense of fairness begins young. Even if an experiment is unfairly rigged so that one child receives more rewards, they will ensure a reward is fairly split.
A finding such as this might impact Christian doctrine on sin. First of all, either it is true or it is not. If true, it suggests that human youngsters are naturally just, generous, and kind–at least more so than adults. The reason why people get crustier, if not more sinful as the years pass, is social pressure. Nurture, in other words, more than nature.
When I was younger, The doctrine on original sin always struck me as unfair. I wasn’t an active dissenter on it as a teenager. I knew I was a sinner anyway, no matter whose fault it was, which was mainly my own. But the idea that older generations would tag me just seemed offensive and irksome.
Is there some kind of social infection for a growing human being? If so, when does it happen? Middle school? First day of kindergarten? First experience of parental authority run amok? Forget about original sin–how would such a finding affect our presumptions and attitudes toward those who slip away from the faith? While a lot of people blame college for the drifting away of the American Catholics, studies show that to be a myth. My sense is that Catholics lose faith shortly after First Communion. Forget about confirmation as a “graduation” sacrament. I’m thinking it’s more the day for eight-year-olds in white dresses and little navy suits.
Suppose a parent tried his or her hardest to shield their child from sin. How fruitless would it be, even if they encouraged sharing and generosity and helping beyond early childhood?
What does it mean for us to have roots of sin in social interaction? That doesn’t strike me as particularly hopeful or fair. But I’m just curious: if it was found that there’s a post-birth threshold on sin, what would that mean for the greater cause of redemption?
Catholic Sensibility 
Unfortunately, that article flattens out a lot of critical detail.
If one assumes, arguendo, that young human beings demonstrate social trust and generosity:
1. Is it universal?
2. Does the breadth and depth vary per person, and if so, how?
3. Are the objects of such trust and generosity variable?
4. Can efforts to broaden the circle of such objects reduce the depth of the trust and generosity?
Et cet.
My dearest friend and I have a fundamental disagreement about the innocence of young children. She insists they are naturally innocent, and my experience at a very young age was that I witnessed even malice at very young ages – as early as I can remember (say, age 3), so I am very reluctant to universalise an assumption of such innocence, as I think it romanticizes things.
Young children are both innocent and malicious. I don’t mean malicious in the sense of sin, of course they don’t have that capability yet. But things like selfishness and jealousy, sure. It’s built in. I have a long memory, and can remember doing some dirty tricks on my younger brothers. And my kids were sweet and mean to each other as preschoolers, sometimes both within less than five minutes. Original sin? To me it’s just the burden of the long evolutionary slog of survival of (sometimes) the selfish, the aggressive, and the horny. By the grace of God, hopefully we overcome this background noise.
Yes.
How could I forget the immortal This American Life segment, “Bad Baby”:
http://www.thisamericanlife.org/radio-archives/episode/521/transcript
A 2010 column by Paul Bloom (who is part of the TAL segment above), “The Moral Life of Babies”:
http://www.nytimes.com/2010/05/09/magazine/09babies-t.html
“Morality, then, is a synthesis of the biological and the cultural, of the unlearned, the discovered and the invented. Babies possess certain moral foundations — the capacity and willingness to judge the actions of others, some sense of justice, gut responses to altruism and nastiness. Regardless of how smart we are, if we didn’t start with this basic apparatus, we would be nothing more than amoral agents, ruthlessly driven to pursue our self-interest. But our capacities as babies are sharply limited. It is the insights of rational individuals that make a truly universal and unselfish morality something that our species can aspire to.”