Abstract

One of the main objections to life extension is that life extension will cause severe overpopulation. This objection presents both moral and demographic issues. To explore the demographic issue, we present an updated and improved version of the formula in chapter six of _New Methuselahs_ for projecting the demographic impact of life extension. The new version includes additional demographical factors such as non-aging related causes of death. According to projections generated with this revised formula, moderate life extension (a life expectancy of 120 years) will not significantly increase population at the fertility rates current in the developed world, but radical life expectancy (halting aging completely, leading to an average life expectancy of 1000 years) can lead to severe overpopulation even at very low fertility rates. This formula also enables us to ascertain what fertility rate and birth spacing will prevent life extension from causing severe overpopulation. The moral issues arise if radical life extension causes overpopulation severe enough to outweigh the benefits it brings. _New Methuselahs_ proposed a reproductive policy for avoiding severe overpopulation by limiting reproduction for those who use life extension. We then consider a moral objection to this policy that was not discussed in _New Methuselahs_: it is not likely that society will succeed in imposing limits to reproduction, therefore, it is likely that radical life extension is morally wrong. We respond to this objection and defend our response against two further objections.