Immortality

===Prospects for human biological immortality===

====Life-extending substances====
Some{{who|date=July 2021}} scientists believe that boosting the amount or proportion of [[telomerase]] in the body, a naturally forming enzyme that helps maintain the protective caps at the ends of [[chromosome]]s, could prevent cells from dying and so may ultimately lead to extended, healthier lifespans. A team of researchers at the Spanish National Cancer Centre ([[Madrid]]) tested the hypothesis on mice. It was found that those mice which were "[[genetic engineering|genetically engineered]] to produce 10 times the normal levels of telomerase lived 50% longer than normal mice".<ref>{{cite news |url=https://www.telegraph.co.uk/health/healthnews/3489881/Scientists-take-a-step-closer-to-an-elixir-of-youth.html |archive-url=https://web.archive.org/web/20081201081233/http://www.telegraph.co.uk/health/healthnews/3489881/Scientists-take-a-step-closer-to-an-elixir-of-youth.html |url-status=dead |archive-date=1 December 2008 |work=The Daily Telegraph |location=London |title=Scientists take a step closer to an elixir of youth |first=Richard |last=Alleyne |date=20 November 2008 |access-date=5 May 2010}}</ref>

In normal circumstances, without the presence of telomerase, if a cell divides repeatedly, at some point all the progeny will reach their [[Hayflick limit]]. With the presence of telomerase, each dividing cell can replace the lost bit of [[DNA]], and any single cell can then divide unbounded. While this unbounded growth property has excited many researchers, caution is warranted in exploiting this property, as exactly this same unbounded growth is a crucial step in enabling cancerous growth. If an organism can replicate its body cells faster, then it would theoretically stop aging.

[[Embryonic stem cells]] express telomerase, which allows them to divide repeatedly and form the individual. In adults, telomerase is highly expressed in cells that need to divide regularly (e.g., in the immune system), whereas most [[Somatic (biology)|somatic]] cells express it only at very low levels in a cell-cycle dependent manner.

====Technological immortality, biological machines, and  "swallowing the doctor"====
{{Main|Molecular machine}}

Technological immortality is the prospect for much longer life spans made possible by scientific advances in a variety of fields: nanotechnology, emergency room procedures, genetics, [[biological engineering]], [[regenerative medicine]], [[microbiology]], and others. Contemporary life spans in the advanced industrial societies are already markedly longer than those of the past because of better nutrition, availability of health care, standard of living and bio-medical scientific advances.{{citation needed|date=October 2021}} Technological immortality predicts further progress for the same reasons over the near term. An important aspect of current scientific thinking about immortality is that some combination of [[human cloning]], cryonics or nanotechnology will play an essential role in extreme life extension. [[Robert Freitas]], a nanorobotics theorist, suggests tiny medical [[nanorobot]]s could be created to go through human bloodstreams, find dangerous things like cancer cells and bacteria, and destroy them.<ref>Robert A. Freitas Jr., ''Microbivores: Artificial Mechanical Phagocytes using Digest and Discharge Protocol'', self-published, 2001 [http://www.rfreitas.com/Nano/Microbivores.htm]</ref> Freitas anticipates that gene-therapies and nanotechnology will eventually make the human body effectively self-sustainable and capable of living indefinitely in empty space, short of severe brain trauma. This supports the theory that we will be able to continually create biological or synthetic replacement parts to replace damaged or dying ones. Future advances in [[nanomedicine]] could give rise to [[life extension#Nanotechnology|life extension]] through the repair of many processes thought to be responsible for aging. [[K. Eric Drexler]], one of the founders of [[nanotechnology]], postulated cell repair devices, including ones operating within cells and using as yet hypothetical [[biological machine]]s, in his 1986 book [[Engines of Creation]]. [[Raymond Kurzweil]], a [[futurist]] and [[transhumanist]], stated in his book ''[[The Singularity Is Near]]'' that he believes that advanced medical [[nanorobotics]] could completely remedy the effects of aging by 2030.<ref>{{Cite book |first=Ray |last=Kurzweil |author-link=Raymond Kurzweil |year=2005 |title=The Singularity Is Near |publisher=[[Viking Press]] |location=New York City |isbn=978-0-670-03384-3 |oclc=57201348|title-link=The Singularity Is Near }}{{Page needed|date=September 2010}}</ref> According to [[Richard Feynman]], it was his former graduate student and collaborator [[Albert Hibbs]] who originally suggested to him (circa 1959) the idea of a ''medical'' use for Feynman's theoretical micromachines (see [[biological machine]]). Hibbs suggested that certain repair machines might one day be reduced in size to the point that it would, in theory, be possible to (as Feynman put it) "swallow the doctor". The idea was incorporated into Feynman's 1959 essay ''[[There's Plenty of Room at the Bottom]].''<ref>{{cite web
 |url=http://www.its.caltech.edu/~feynman/plenty.html
 |title=There's Plenty of Room at the Bottom
 |author=Richard P. Feynman
 |date=December 1959
 |access-date=1 March 2010
|url-status=dead
 |archive-url=https://web.archive.org/web/20100211190050/http://www.its.caltech.edu/~feynman/plenty.html
 |archive-date=11 February 2010
}}</ref>

====Cryonics====
{{Unreferenced section|date=November 2022}}
{{Main|Cryonics}}

[[Cryonics]], the practice of preserving organisms (either intact specimens or only their brains) for possible future revival by storing them at cryogenic temperatures where metabolism and decay are almost completely stopped, can be used to 'pause' for those who believe that life extension technologies will not develop sufficiently within their lifetime. Ideally, cryonics would allow clinically dead people to be brought back in the future after cures to the patients' diseases have been discovered and [[rejuvenation (aging)|aging is reversible]]. Modern cryonics procedures use a process called [[Cryopreservation#Vitrification|vitrification]] which creates a glass-like state rather than [[freezing]] as the body is brought to low temperatures. This process reduces the risk of ice crystals damaging the cell-structure, which would be especially detrimental to cell structures in the brain, as their minute adjustment evokes the individual's mind.

====Mind-to-computer uploading====
{{Main|Mind uploading}}

One idea that has been advanced involves [[Mind uploading|uploading]] an individual's habits and memories via [[direct mind-computer interface]]. The individual's memory may be loaded to a computer or to a new organic body. [[Extropian]] [[futures studies|futurists]] like Moravec and [[Ray Kurzweil|Kurzweil]] have proposed that, thanks to [[exponential growth|exponentially growing]] computing power, it will someday be possible to [[mind uploading|upload human consciousness]] onto a computer system, and exist indefinitely in a virtual environment.

This could be accomplished via advanced cybernetics, where computer hardware would initially be installed in the brain to help sort memory or accelerate thought processes. Components would be added gradually until the person's entire brain functions were handled by artificial devices, avoiding sharp transitions that would lead to issues of [[identity (social science)|identity]], thus running the risk of the person to be declared dead and thus not be a legitimate owner of his or her property. After this point, the human body could be treated as an optional accessory and the program implementing the person could be transferred to any sufficiently powerful computer.

Another possible mechanism for mind upload is to perform a detailed scan of an individual's original, organic brain and simulate the entire structure in a computer. What level of detail such scans and simulations would need to achieve to emulate awareness, and whether the scanning process would destroy the brain, is still to be determined.{{efn|
The basic idea is to take a particular brain, scan its structure in detail, and construct a software model of it that is so faithful to the original that, when run on appropriate hardware, it will behave in essentially the same way as the original brain.
::: — Sandberg & Boström (2008)<ref name=Sandberg-Boström-2008-Roadmap>
{{cite book
 |last1=Sandberg |first1= Anders
 |last2=Boström  |first2=Nick 
 |year=2008
 |title=Whole Brain Emulation: A roadmap
 |series=Technical Report
 |volume=#2008-3
 |publisher=Oxford University
 |department=Future of Humanity Institute
 |url=http://www.fhi.ox.ac.uk/Reports/2008-3.pdf
 |access-date=5 April 2009
}}
</ref>
}}

It is suggested that achieving immortality through this mechanism would require specific consideration to be given to the role of [[consciousness]] in the functions of the [[mind]]. An uploaded mind would only be a copy of the original mind, and not the conscious mind of the living entity associated in such a transfer. Without a simultaneous upload of consciousness, the original living entity remains mortal, thus not achieving true immortality.<ref>
{{cite web
 |last=Ruparel |first=Bhavik
 |date=30 July 2018
 |title=On achieving immortality
 |website=Iva.to
 |url=https://medium.com/iva-to/on-achieving-immortality-3ed1d567f7a2
 |access-date=10 September 2018
}}
</ref>
Research on [[neural correlates of consciousness]] is yet inconclusive on this issue. Whatever the route to mind upload, persons in this state could then be considered essentially immortal, short of loss or traumatic destruction of the machines that maintained them.{{clarify|date=October 2015}}{{citation needed|date=September 2021}}

====Cybernetics====
{{Unreferenced section|date=November 2022}}
{{Main|Cyborg}}

Transforming a human into a [[cyborg]] can include [[brain implants]] or extracting a human processing unit and placing it in a robotic life-support system.<ref>{{cite web |last1=Melbourne |first1=Dr Alan Lai, University of |title=Part human, part robot: The future of medical implantables |url=https://pursuit.unimelb.edu.au/articles/part-human-part-robot-the-future-of-medical-implantables |website=Pursuit |access-date=2 January 2024 |language=en |date=12 September 2017}}</ref> Even replacing biological organs with robotic ones could increase life span (e.g. pace makers) and depending on the definition, many technological upgrades to the body, like genetic modifications or the addition of nanobots would qualify an individual as a cyborg. Some people believe that such modifications would make one impervious to aging and disease and theoretically immortal unless killed or destroyed.{{citation needed|date=January 2021}}

====Digital immortality====
{{Main|Digital immortality}}