The Future of Aging: Pathways to Human Life Extension
This book review was originally published in Cryonics magazine, 1st Quarter, 2011.
Editor-in-chief, cryobiologist, and aging researcher Gregory M. Fahy and his associate editors Michael D. West, L. Stephen Cole and Steven B. Harris have compiled what might be the most impressive collection of articles on interventive gerontology to date in their 866 page collection The Future of Aging: Pathways to Human Life Extension
I have read the book with the following two questions in mind:
1. Which approaches for increasing the maximum life span show clear near-term potential?
2. Is meaningful rejuvenation possible without advanced cell repair technologies?
What follows are my comments on selected chapters of the book.
I cannot say that I am a big fan of Ray Kurzweil’s work. His general introduction to life extension, “Bridges to Life,” co-written with Terry Grossman, starts out on a restrained note, discussing the benefits of caloric restriction, exercise, basic supplementation, and predictive genomics. But it then ratchets up into bold claims about the future that rest on controversial premises: about biology and health following the same path as information technology; about the technical feasibility of molecular nanotechnology; and about the nature of mind. One thing that remains a mystery to me is how such an accelerating pace of anti-aging technologies could be validated considering the relatively long life expectancy of humans. Presumably we are expected to adopt a lot of these technologies based on their theoretical merits, success in animal studies, or short-term effects in humans.
Associate Editor Stephen Cole contributes a chapter on the ethical basis for using human embryonic stem cells. I suspect that his argument in favor of these therapies relies on adopting a definition of personhood that has more far-reaching, and more controversial, consequences than just permitting the use of human embryonic stem cells. One of the most disconcerting aspects of the bioethical debate on stem cell research is that many of its advocates seem to feel that if they do not see an ethical case against it, government funding for such research should be permitted. In essence, this means that opponents of embryonic stem cell research are obliged to financially support it as well. This is a recipe for further aggravating what has already become a passionate political debate.
As someone with relatively limited exposure to the biogerontology literature I should be cautious in singling out one technical contribution for high praise, but Joshua Mitteldorf’s chapter on the evolutionary origins of aging is one of the best and most inspiring articles in the field of aging research I have read and worth the hefty price of the book alone. Mitteldorf outlines a case for the theory that evolution has selected aging for its own sake and presents experimental findings that falsify other explanations for aging such as wear-and-tear and metabolic trade-offs. That aging is firmly under genetic control may appear the most pessimistic finding in terms of the prospects of halting aging but in fact allows for the manipulation of a number of selected upstream interventions that can inhibit or mitigate these programs.
It is clear from this ambitious book that cryobiologist Greg Fahy also has a strong interest in biogerontology but nothing prepared me for the encyclopedic knowledge that he displays in his lengthy chapter on the precedents for the biological control of aging. Fahy’s chapter further corroborates the view that aging is under genetic control. He also reviews a great number of beneficial mutations and interventions in animals and humans that can extend lifespan. Reading all these inspiring examples, however, I found myself faced with the same kind of despair as when reading about all the neuroprotective interventions in stroke and cardiac arrest. There is great uncertainty how such interventions would fare in humans (or other animals) and, more specific to the objective of human life extension, how we ourselves can ascertain that there are no long-term adverse consequences. Fahy does not run away from the most formidable challenge of all, rejuvenation of the brain without losing identity-critical information, but points out that identity-critical information might be retained despite the turnover and replacement of components that a meaningful life extension program for the brain would most likely require. Fortunately, people who make cryonics arrangements can feel a little better about this issue because their survival is not dependent on safe technologies becoming available in their lifetime.
Zheng Sui’s report on using high potency granulocytes to cure cancer in mice is one of the more exciting chapters in the book and a fine example of the role of chance discoveries in biomedical research (Zheng by accident discovered a mouse innately resistant to cancer). With substantial support of the Life Extension Foundation and other private donors, Sui is aggressively pursuing Leukocyte Infusion Therapy (LIFT) human trials instead of pursuing the torturous path of trying to illuminate the biochemical and molecular mechanisms that drive the successful results in mice. I should mention that a unique concern for cryonicists is that eliminating cancer in the absence of other effective anti-aging technologies could increase the likelihood of dying as result of identity-threatening insults such as cardio-vascular complications, ischemic stroke, or Alzheimer’s disease.
I must admit being somewhat disappointed in the chapter about “evolutionary nutrigenomics” by Michael Rose and his collaborators. Michael Rose has always struck me as one of the more level-headed and empirical aging researchers, and his work with fruit flies is a resounding demonstration of using evolutionary tools to investigate and combat aging. His short contribution to this book reads more as a quickly thrown together status update of their company, Genescient, than a rigorous treatment of the issues. Dispersed throughout the text are a number of interesting perspectives on alternative approaches to aging research and the validation of anti-aging interventions, but these issues are not discussed in much detail. Michael Rose’s work is of great interest, but this chapter is neither a good introduction to his work nor an in-depth treatment of the practical applications of his research.
Anthony Atala’s chapter, “Life Extension by Tissue and Organ Replacement,” is a fascinating update on the current status and potential of regenerative medicine and tissue engineering. Unlike most of the chapters in this book, the author reports a number of examples of successful clinical applications. It is a good example of how working with nature (instead of trying to improve upon it) can have meaningful near-term benefits. Unfortunately, there is no discussion of the progress in regenerative medicine for the brain. Obviously, such strategies cannot involve a simple replacement of the brain with a newly grown brain but selected repair technologies can play an important role in brain-damaging diseases and insults. The inclusion of “life extension” in the chapter title seems somewhat artificial to me because there is no distinct treatment about how tissue and organ replacement will be expected to contribute to life extension. Additionally, there is little discussion of contemporary artificial and mechanical alternatives to organs (or biological structural components) in this chapter, or in any other chapters in the book, which I think is a minor oversight.
Robert J. Shmookler Reis and Joan E. McEwen contribute a chapter about identifying genes that can extend longevity. Their discussion of the prospects for mammals includes the sobering observation that “many of the gains we can attain by a single mutation in the simpler organism may already have been incorporated in the course of achieving our present longevities.” Then again, unless aging is firmly under genetic control in simple organisms but the result of wear and tear in humans there should be (unique) approaches in humans that should confer similar benefits as well.
The publication of this book came to my attention when I learned about Robert Freitas’s contribution, “Comprehensive Nanorobotic Control of Human Morbidity (PDF),” so I was quite interested in reading this final chapter of the book. I am not qualified to comment on the technical aspects of his vision of nanotechnology. I think it is fair to say, though, that if resuscitation of cryonics patients is possible they will most likely be resuscitated in a future that has nanomedical capabilities resembling those that are outlined in this chapter. For this reason alone, this chapter should be of great interest to readers of this magazine. Of particular interest is the discussion of cell repair technologies and brain rejuvenation, a topic of great interest to cryonics. Freitas devotes considerable space discussing how anti-aging strategies like SENS can be achieved with medical nanorobots but the chapter falls short of offering a distinct exposition of a nanomedical approach to aging and rejuvenation. With such profound molecular capabilities one would think that such an approach would not just consist of updating existing biotechnological approaches to eliminate aging related damage with more powerful tools. I think that the distinct capabilities that molecular technologies have to offer would have benefitted from a more extensive discussion of their transformative capabilities. In particular, the section on nanorobot-medicated rejuvenation could have benefitted from a more rigorous treatment of the question of how these interventions would produce actual rejuvenation. Rejuvenation will be a practical requirement for most cryonics patients and it would be interesting to see a more detailed technical discussion of this topic.
Robert Freitas introduces the phrase NENS (Nanomedically Engineered Negligible Senescence) for his vision of how the goals of SENS can be achieved through nanomedicine. This raises an important question: is there any reason to believe that the timeline for “conventional” SENS will be different from the timeline for mature molecular medicine? It is hard to tell, but one could argue that the development of mature nanotechnology is more comprehensive than any strategies designed to deal with the causes or effects of the aging process. So why not just fund the work of biological and mechanical molecular nanotechnologists to accelerate meaningful re-design of the human organism? I think that the best answer is that our current state of knowledge does not justify giving a privileged position to any particular approach and having these visions of the future compete may be the best hope that we have for seeing meaningful rejuvenation and the resuscitation of cryonics patients in the future.
If there is one serious omission in this impressive collection of articles it is a more comprehensive chapter on the topic of biomarkers of aging in humans. As reiterated throughout this review, the gold standard and most rigorous determination of the efficacy of anti-aging therapies and interventions is to empirically determine whether they increase maximum human lifespan. For obvious reasons, most medical professionals and healthcare consumers are pressed to make decisions based on less rigorous criteria and the development of a set of reliable biomarkers of aging is highly desirable. Of course, the most rigorous case for successful biomarkers would require the same kind of long-term studies, leading to an infinite regress problem. How to break out of this predicament while retaining a framework to make rational decisions about life extension technologies is not a trivial problem and can be the topic of a whole new volume of articles. Interestingly enough, one of the most insightful perspectives on this issue is given in Appendix A by SENS researcher Michael Rae when he points out that therapies aimed at rejuvenation can be tested at much more rapid timescales than therapies to retard the aging process or increase the maximum lifespan.
Michael Rae also notes that SENS’s “engineering heuristic” is well established in other fields of biomedicine. It is certainly the case that aging research could benefit from a stronger emphasis on solving problems and repairing damage instead of completely trying to understand the underlying pathologies but it also needs to be pointed out that the engineering approach has not fared much better in areas of research that are notoriously resistant to effective solutions such as neuroprotection in stroke. Ultimately, the SENS approach cannot completely escape studying the mechanisms and metabolic pathways involved when treatments are compared and side-effects are studied. In this sense, the difference between SENS and alternative approaches is a matter of degree, not principle.
I think that the editors are justified in claiming that the prospects for solving the aging challenge have never looked better. A close inspection of all the chapters, however, shows that no significant interventions in the aging process in humans are available now, and I doubt they will become available in the near future. And even if the aging process can be eliminated, there will still be medical conditions and accidents that require placing a person in cryostasis until effective treatment is available. For the foreseeable future there is good reason to agree with Thomas Donaldson’s advice* that making cryonics arrangements is the most fundamental and sensible decision one can make in order to reap the benefits of powerful future life extension therapies.
*Thomas Donaldson – Why Cryonics Will Probably Help You More Than Antiaging, Physical Immortality 2(4) 28-29 (4th Q 2004)