Talk:Mountain Men/@comment-67.172.101.58-20150615032340/@comment-26247132-20150615041343

My guess is the limited exposure they did have to radiation caused enough of a mutation of their genes that with each subsequent generation, they were more and more susceptible to the effects of radiation. When they saw the Grounders able to survive outside 56 years previously when they couldn't, that's when they started their experiments. Prior, they just had to suffer through regular treatments (and most likely die) when exposed to radiation.