Len,
Can some Christian please tell me what "original sin" is currently taken to mean?
Though they cannot demonstrate it to be true, Christians think there to be something they call "God".
They also think this "God" to be be pretty terrific, and concerned not to allow bad things to happen and to make everyone happy (well I say everyone, but they also think that "He" has a bit of a hissy fit when some people back the wrong horse by choosing another god, but anyways...).
Clearly though bad things
do happen and lots of people are not happy at all. What then to do as what's observably true contradicts the nursery story? Easy peasy - just make the bad stuff all our fault!
Now this needed a story of some kind, so the early authors of this stuff dreamt up "Adam" and "Eve" (an iron-age notion that modern evolutionary theory has long-since fundamentally blown out of the water) and decided that they broke one of "God's" rules, so in exchange this "God" called their behaviour "original sin" and punished them for it by giving brain cancer to babies thousands of years later.
Just to complete the job of knife-twisting, Christians have also got it into their heads that to be forgiven for this offence that someone else entirely committed long ago and far away we need to be "redeemed", redemption entailing all sorts of dehumanising obeisances to this "God" of theirs.
It's morally disgusting and as mad as a monkey on a tricycle carrying a box of frogs I know, but there it is nonetheless. There really are people alive now who we entrust to drive cars and to lay turf the right way up who actually believe this stuff, however bewildering their credulity is for the rest of us.
Hope that helps