Is Ross suggesting that current levels of irradiation are
limiting lifespans or does he mean that _past_ events of
radiation-inflicted damage reduced the human lifespan?
If it's the latter, then the results from current experiments
could be shrugged off by claiming that most of the life-shortening
damage is already done.
Of course, how we could have escaped damage before the fall
from the radioactive potassium which resides in all our bodies
would remain an open question.
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