A successful scientific explanation for the long lifespans of prediluvian patriarchs has not yet been put forward. However, one overlooked possibility involves the negative role of radiocarbon (C-14) as a source of cancer-inducing mutations. Because radiocarbon is incorporated into the very atoms of the DNA strand, the transmutation of radiocarbon atoms back into nitrogen has a disproportionate ability to create mutations compared to other sources of radiation. If we accept that today's fossil fuel reserves were created by the burial of prediluvian forests and marine life, then the amount of carbon in the prediluvian atmosphere, biosphere, and oceans was much greater than at present. This means that radiocarbon produced from cosmic rays before the Flood would have been diluted into a much larger carbon sink, greatly decreasing the concentration of radiocarbon in humans, thereby lowering the rate of cancer, and allowing longer lifespans. To support this thesis, we will calculate likely levels of radiocarbon before and after the Flood and compare them with prediluvian and postdiluvian lifespans. Next, we will show that radiocarbon decay has the potential to cause the most cancers and be a significant factor in decreasing human lifespans. Finally, we will discuss future experiments and a way we can begin to increase human lifespan in the present. Isaiah prophesied, "There shall be no more thence an infant of days, Nor an old man that hath not filled his days: For the child shall die an hundred years old; But the sinner being an hundred years old shall be accursed" and "for as the days of a tree are the days of my people…." (Isaiah 65:20, 22c)