I’ve always said those pre-diluvial people you read about in the Bible living to 900+ years is NOT any kind of metaphor. It’s because the air was far more rich with oxygen before the sudden glacial meltdown. Ice core samples prove it. Another proof is the giant flora and fauna that lived in pre-diluvial times. They could get so big because the atmosphere was much more dense then. Gravity was the same, but the buoyancy of the air was much greater than today.
My conception was that as man got farther away from the Fall of our first parents, who were immortal as created, the life span gradually decreased. Tolkien had a similar concept with the Numenoreans, who were the offspring of mortal man and immortal elves/Maia. They descended from the son who chose mortality, whereas Elrond elected immortality with the elves. The kings of Numenor had lifespans of hundreds of years but eventually dwindled to our current state. (Taking off my geek hat now)
See post 56.
I’ve believed the same thing for about 20 years after studying how pressurized oxygen speeds up the healing process of burn victims and eye injuries.
The regeneration caused by those chambers was measurable, so it stands to reason that a higher O2 concentration in the atmosphere could result in the long lives of the first people and their decedents.