Just a quick religion blip mixed in with supposed science, warning!!!:
From what understand in the bible, in the early days of Earth, people lived up to 900 years, close to 1000. Others 700 and such. A long ass time. I hear there was a water zone, being a buffer between the atmosphere and space, reflecting radiation. Radiation is

highter now cauze the water barrier is gone, IE. "The Flood"- when God cauzed it to crash down.
I hear thaz why 'dinasuors' were big, and now extinct, things grew

bigger back then, cauze of the way low radiation, cauze of the barrier water thing.
Also why the bible records "Giants", big men that lived, and died off eventually.