We’ve been gathering info on average paternal age in different societies: here’s some for some rural villages in Gambia, from an article by Ruth Mace.
This shows age-specific fertility for males and females over the lifespan. The average paternal age is 47, the oldest we’ve found so far. It’s a consequence of polygyny, which both delays and extends male fertility. Extrapolating from Decode’s results, this population would have a mutation rate 67% higher than one with an average paternal age of 28.
The only likely event that would cause genetic problems comparable to those expected from a long-term pattern of high paternal age would be a central nuclear war. Maybe. We don’t really know the extent to which a given amount of radiation increases the human mutation rate, although we could easily find out in the near future, by sequencing family triads with known exposure to medical radiation. Judging from mice, the doubling dose is about a hundred rads, about one fifth of a fatal dose. The existing background level of radiation is a minor factor in the human mutation rate: it would have to increase a lot to become the most important factor.