These mutation rates are unexpectedly high, considering the level of radiation. It seems reasonable that even higher levels of radiation would lead to higher mutation rates. If radiation levels were higher in the past, this would have produced a much higher mutation rate in the human race in the past. This, together with the fact that some parts of the genome mutate rapidly, can help to explain why the level of genetic diversity in the human race is higher than one would expect based on a short Biblical chronology of the human race.... researchers led by geneticist Yuri Dubrova of the University of Leicester, United Kingdom, describe a compelling connection between radioactive fallout and elevated mutation rates in families living downwind of the Semipalatinsk nuclear facility ...
The findings bolster a controversial 1996 report by Dubrova and a different group of colleagues that linked germ line mutations to fallout from the 1986 Chornobyl explosion. That study, published in Nature, described double the usual mutation rate in the children of men living in a region of Belarus heavily contaminated with cesium 137.
In each subject they examined eight minisatellite DNA regions that are prone to mutations. ... Compared to control families in a nonirradiated part of Kazakhstan, individuals exposed to fallout had a rougly 80% increase in mutation rate, and their children showed an average rise of 50%.