Why did man live
longer BEFORE the flood?
What could have caused mankind to have lived such LONG lifespans before the flood of Noah? For example, Adam lived 930 years, Jared lived to 962, and Jared's grandson Methuselah lived the longest in history at 969 years! While the average age at death before the deluge was high, it averaged only 317 years for the ten generations following it. Many who refuse to believe in the Bible say that the ages upon death found in the first several chapters of Genesis are nothing but fabrications and tall tales.
Several things could have contributed to the shorter lifespans after the flood. Scripture denotes that the waters God brought on the earth would destroy not only animals by the earth itself.
And God said to Noah, 'The end of all flesh has come before Me, for the earth is filled with violence through them. And, behold, I will destroy them with the earth.' (Genesis 6:13, Holy Bible in Its Original Order - A Faithful Version)
'And I will establish My covenant with you . . . Neither shall there any more be a flood to destroy the earth.' (Genesis 9)
The earth after the flood was dramatically different than it was before it. The differences included the altering of the climate, atmospheric changes, changes in the hydrologic cycle, geologic features, a significant increase in harmful radiation reaching ground level, man's dietary habits went from solely plant-based to one where meat was eaten, and so on. These and many other factors led to man's much shorter lifespans.
The first century historian Josephus asserts that man, at one time, did live very long lifespans. He attributes their longevity to God's mercy and the fact that the food they ate was much better at extending their years on earth than it was after the deluge (Antiquities of the Jews, Book 1, Chapter 3).
The long pre-flood lifespans delineated in the book of Genesis are not myths. Proof of this fact can be found by understanding nature's exponential decay rate. All things fall apart or decay at a given rate. If a container of organisms is exposed to a substance that is radioactive, they will die at a speed called a natural decay rate. This graph curve is the same even if the organisms are exposed to deadly doses of gas or other substances.