Life expectancy: when did God decide we where going to live to be 100 instead of 700 or 800 hundred and why, and what scriptures refer to that information?

Answer:

As far as life expectancy, One Christian apologist claim is that the life span of humans has changed; that originally man was to have everlasting life, but due to man’s sin, God progressively shortened man’s life — first to less than 1000 years (Adam & ancestors), then to under 500 (after the flood), 200, and eventually 120 years. After those long living people died, God decided that humans would not be permitted to live more than 120 years (Genesis 6:3.) However, since later biblical figures such as Sarah lived for longer than that, 120 years should be considered the “usual” upper limit to man’s lifespan. Some individuals can live slightly longer than that. Furthermore, starting with Calvin and Luther, an alternative explanation has arisen : 120 years would not refer to man’s lifespan but to the amount of time left before the flood.

See also: How long should you expect to live?