Of the people at Bikini Atoll during the testing, just randomly some were more susceptible to radiation and sickness, others less. Those that were more susceptible died sooner, those that weren't lived long enough to be your father.
"It can't be selection bias because OP only has one father."
Come on, folks. It is selection bias, because we wouldn't hear a "my dad survived" story if his dad didn't survive. Otherwise known as "survivorship bias," which is a form of selection bias.
Only if the deaths (or more correctly: any effects harsh enough to impede mating) happen before the typical age of becoming a parent. If it's just "live healthy to very old age" vs "cancer at fifty", then there is no selection bias since our anecdata here is based on the next generation.
I think the GP means the OP's father survived long enough for OP to be born, so from OP's perspective it looks like his father had good genetics. The selection bias is that none of the children of those who died early would exist, so only the children of those lucky enough to live a long time could say their parents must've had good genes.
Or it's how the photons happened to hit his body. They might have hit in just the right way to not do cancer-causing DNA damage, or if that did happen, then those cells weren't influential or died or were terminated by the immune system by pure luck (he could have had the same level of "immunity" as those who happened to die because their system simply had an unlucky miss).
It's not about him. It's the odds that someone would have children from that original group.
Consider, it's in no way an unusual event for lotteries to have winners. Further someone can increase their odds of winning by buying a lot of tickets. However, winners are unlikely to buy thousands of tickets for that drawing because the pool of people that buy a few tickets are vastly higher than the pool of people that buy thousands of tickets to each drawing.
So, just because one guy did not get cancer does not mean he has unusual DNA. Granted, the odds of him having some anti cancer mutation is probably higher than the general population.
So you mean he's luckier because he has lots of fathers, therefore more lottery tickets, thus increasing the chance that at least one of his fathers will live a long life without getting cancer?
Doesn't matter from our probabilistic perspective. Odds of seeing someone with a father who survived atomic testing is different from odds that your father survived atomic testing.
Of the people at Bikini Atoll during the testing, just randomly some were more susceptible to radiation and sickness, others less. Those that were more susceptible died sooner, those that weren't lived long enough to be your father.