Just my opinion here as I happen to have been thinking about this recently but here goes.
I think that it may be possible that
the effects of our own sins have a degenerative effect on our DNA. Starting with original sin which had immediate and irreversible consequences on the genes of Adam and Eve that introduced sickness, death, and decomposition.
In the beginning the human DNA was perfect and there was no time limit on how long we could live. As the sins of the human race were piled on to our history it continued to corrupt and distort our our genes, which naturally led to a decrease in our overall longevity. This downward trend continued until the point were the positive effects of medicine caught up to and halted the natural decline in our health, and people slowly started living slower.
I haven’t had the chance to look it up yet to see if this is plausible, but if this theory is true there should be a slow rise in the number of genetic abnormalities and diseases. I would think that would include cancer, muscular dystrophy, or even autism. I’m sure some one has thought of this before, but like I said I just happen to be thinking about it lately, but haven’t had a chance to actually research this stuff to see if it is, in fact, provable. I would actually like to know if anyone else knows anything about this