>>512142052
It just fell off a cliff around 1961.

>>512142252
Pretty sure the Christians say it was God or something. As an atheist I'm not fully convinced.

>>512129291
Not since nuclear testing started. Hence the imports to refresh the gene pool. When nuclear testing it's closer to passing in your tub on one end and believing the other end is clear of piss. Radiation works the same way. It goes everywhere.