Why did man live longer BEFORE the flood?

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What could have caused mankind to have lived such LONG lifespans before the worldwide flood? The average lifespan before the flood (ten generations) was 857 years. After it the average life span (for the ten generations from Shem to Abraham) was only 317 years! 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 deluge. 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 (HBFV))

"'And I will establish My covenant with you. Neither shall all flesh be cut off any more by the waters of a flood. Neither shall there any more be a flood to destroy the earth.'" (Genesis 9)

The earth changed dramatically after the great flood. 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 pre-flood man 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).

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Chart showing longevity of Biblical patriarchs before and after flood
The long 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.

If you take the points of the population in question and graph them you can see how close the actual and exponential decay rates compare. This yields an equation and a value called the coefficient of determination. This math ratio tells us how close our graph correlates to the decay curve. This coefficient will be a number somewhere between the range of 0 and 1. A coefficient of 1 is a perfect match.

The pre-flood Biblical patriarchs lived incredibly long lives compared to today. Post-flood the life expectancy of a person dropped to the modern average lifespan of a person of around 70 to 80 years. Plotting the lifespans of the patriarchs on a graph can show us their decay curve, which can then be compared to the perfect exponential decay curve (which has a 1 for its coefficient of determination). With this information it can be reasonably proven that the stated number of years lived for the people found in Genesis is literally true.

The coefficient of determination in the below graph (labeled as R2) is almost .89. The decay rate of the Biblical patriarchs listed in the graph is only 11% away from matching the exponential (natural) decay curve.

Longevity of Biblical
Patriarchs after the Deluge
Chart showing the longevity of the Biblical Patriarchs
Note that it took several generations for a new
average lifespan of 70 years to be reached.

Adapted from material by:  Arnold C. Mendez

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