Abstract
Biological studies have demonstrated that it is possible to slow the ageing process and extend lifespan in a wide variety of organisms, perhaps including humans. Making use of the findings of these studies, this article examines two problems concerning the effect of life extension on population size and welfare. The first—the problem of overpopulation—is that as a result of life extension too many people will co-exist at the same time, resulting in decreases in average welfare. The second—the problem of underpopulation—is that life extension will result in too few people existing across time, resulting in decreases in total welfare. I argue that overpopulation is highly unlikely to result from technologies that slow ageing. Moreover, I claim that the problem of underpopulation relies on claims about life extension that are false in the case of life extension by slowed ageing. The upshot of these arguments is that the population problems discussed provide scant reason to oppose life extension by slowed ageing.
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Notes
These figures are extrapolated from [17].
Fertility is defined as the number of children born to each woman in a lifetime. Note that this is different from the birth rate, which is the rate at which babies are born.
I am grateful to Fridolin Gross’s programming expertise and conceptual nous for the design of this model.
Using replacement rate also makes it possible to do a linear comparison. Linear comparisons are conceptually easier than exponential ones.
The number of ageing ‘organisms’ here does not match the number of humans in the real world because simulating 7 billion organisms would require too much computing power. The pattern of the effect can be expected to match that in Fig. 1.
Again, this assumes reproduction at replacement rate. If there is more than one offspring per organism, the increase in population would be greater, since more people would be born in the period in which the frequency of death decreased. Once again, however, the rate of population growth would soon return to that experienced in the normal scenario.
I accept a broadly consequentialist conception of human welfare. Traditional utilitarians suggest that the level of happiness or pleasure is the good consequence that matters, but I will not specify this. There may be more pluralistic conceptions of good and bad consequences, and I believe the arguments here also apply to those.
Of course it is possible to bite the bullet and claim that such interventions should not be provided. However, the need to present the moral case for allowing children to die might render the bitten bullet difficult to swallow.
The characterisation of this argument as ‘underpopulation’, and the formalisation that follows, is my own.
Note that the ‘repugnant car jam’ involves synchronic versions of average and total utilitarianism: welfare at a given time. This section is concerned with diachronic welfare: welfare across time.
See [33] for an account of the methods used by the Chinese authorities and their effects.
This illustration uses the heuristic simplification that the people live one after the other.
Our model bore this prediction out. In Fig. 1, the ‘total number lived’ is higher in the case of normal lifespans than in the case of slowed ageing, despite an equivalent fertility rate.
Calculating health benefit in this way might seem implausible. However, in health allocation decisions it is common to use measures of health benefit like this, such as the quality adjusted life year (QALY). See [39] for a discussion.
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Acknowledgements
I am particularly grateful to Fridolin Gross for interesting discussions and conceptual support. Thaddeus Metz provided important input and structural advice. Thanks also to the participants at the 11th meeting of the International Society for Utilitarian Studies in Lucca, Italy, as well as the attendees at the 2013 Philosophy Spring Colloquium in the KwaZulu-Natal Midlands. Daniel Kim and two anonymous reviewers provided valuable suggestions.
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Wareham, C. Slowed ageing, welfare, and population problems. Theor Med Bioeth 36, 321–340 (2015). https://doi.org/10.1007/s11017-015-9337-5
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DOI: https://doi.org/10.1007/s11017-015-9337-5