YEs, the average human lifespan has been increasing for the last bunch of years, basically due to the increase of better health care. However,
even in roman times, there were a number of individuals from the high classes of soceity that had the better environment to live, and therefore lived into their 80's and 90's.. so the potential has not increased.
As for the biblical stories.. well, one item about aging, skeletons show signs of their age, and it is possible to determine how old someone was when they died. There is no physcial evidence that the life span as reported in the bible is anything but a story.
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