Examine individual changes

'{{Other uses}} {{Refimprove|date=December 2009}} [[Image:Youth and Time 1901.jpg|thumb|''Youth and Time'', [[John William Godward]], 1901]] '''Eternal youth''' is the concept of human physical [[immortality]] free of [[aging]]. The [[youth]] referred to is usually meant to be in contrast to the depredations of aging, rather than a specific age of the human lifespan. Achieving eternal youth so far remains beyond the capabilities of scientific technology. However, much research is being conducted in the sciences of genetics which may allow manipulation of the aging process in the future.{{citation needed|date=November 2010}} Eternal youth is common in mythology, and is a popular theme in [[fiction]]. ==Religion and mythology== Eternal youth is a characteristic of the inhabitants of [[Paradise]] in [[Abrahamic religion]]s. The Hindus believe that the Vedic and the post-Vedic rishis have attained immortality, which implies the ability to change one's body's age or even shape at will. These are some of the [[siddha]]s in [[Yoga]]. [[Markandeya]] is said to always stay at the age of 16. The difference between eternal life and the more specific eternal youth is a recurrent theme in [[Greek mythology|Greek]] and [[Roman mythology]]. The [[mytheme]] of requesting the boon of immortality from a god, but forgetting to ask for eternal youth appears in the story of [[Tithonus]]. A similar theme is found in [[Ovid]] regarding the [[Cumaean Sibyl]]. In [[Norse mythology]], [[Iðunn]] is described as providing the gods [[apple]]s that grant them eternal youthfulness in the 13th century [[Prose Edda]]. ==Telomeres== An individual's [[DNA]] plays a role in the aging process. Aging begins even before birth, as soon as cells start to die and need to be replaced. On the ends of each [[chromosome]] are repetitive sequences of DNA, [[telomeres]], that protect the chromosome from joining with other chromosomes and have several key roles. One of these roles is to regulate cell division by allowing each cell division to remove a small amount of genetic code. The amount removed varies by the cell type being replicated. The gradual degradation of the telomeres restricts cell division to 40-60 times, also known as the [[Hayflick limit]]. Once this limit has been reached more cells die than can be replaced in the same time span. Thus soon after this limit is reached the organism dies. The importance of telomeres is now clearly evident: lengthen the telomeres, lengthen the life.<ref name="Siegel"/> However a study of the comparative biology of mammalian telomeres indicated that telomere length correlates inversely, rather than directly, with lifespan, and concluded that the contribution of telomere length to lifespan remains controversial.<ref>Gomes NM, Ryder OA, Houck ML, Charter SJ, Walker W, Forsyth NR, Austad SN, Venditti C, Pagel M, Shay JW, Wright WE (2011). Comparative biology of mammalian telomeres: hypotheses on ancestral states and the roles of telomeres in longevity determination. Aging Cell 10(5):761-768. doi: 10.1111/j.1474-9726.2011.00718.x. PMID 21518243</ref> Also, telomere shortening does not occur with age in a some postmitotic tissues, such as in the rat brain.<ref>Cherif H, Tarry JL, Ozanne SE, Hales CN (2003). Ageing and telomeres: a study into organ- and gender-specific telomere shortening. ''Nucleic Acids Res'' 31(5):1576-1583. PMID 12595567</ref> In humans, skeletal muscle telomere lengths remain stable from ages 23–74.<ref>Renault V, Thornell LE, Eriksson PO, Butler-Browne G, Mouly V (2003). Regenerative potential of human skeletal muscle during aging. Aging Cell 1(2):132-139. PMID 12882343</ref> In baboon skeletal muscle, that consists of fully differentiated post-mitotic cells, less than 3% of myonuclei contain damaged telomeres and this percentage does not increase with age.<ref>Jeyapalan JC, Ferreira M, Sedivy JM, Herbig U (2007) Accumulation of senescent cells in mitotic tissue of aging primates. ''Mech Ageing Dev'' 128(1):36-44. PMID 17116315</ref> Thus telomere shortening does not appear to be a major factor in the aging of the differentiated cells of brain or skeletal muscle. Studies have shown that 90 percent of [[cancer]] cells contain large amounts of an [[enzyme]] called [[telomerase]].<ref name="Damm"/> Telomerase is an enzyme that replenishes the worn away telomeres by adding bases to the ends and thus renewing the telomere. A cancer cell has in essence turned on the telomerase gene, and this allows them to have an unlimited amount of divisions without the telomeres wearing away. Other kinds of cells that can surpass the Hayflick limit are [[stem cells]], [[hair follicles]], and [[germ cells]].<ref name="Hornsby"/> This is because they contain raised amounts of telomerase. ==Therapy== The idea that the human body can be repaired in old age to a more youthful state has gathered significant commercial interest over the past few years, including by companies such as [[Human Longevity Inc]], [[Google Calico]] and [[Elysium Health]] (supported by seven Nobel Prize winning scientists). In addition to these larger companies, many startups are currently developing therapeutics to tackle the 'ageing problem' using therapy.<ref>{{cite news|title=Esthechoc: Scientists invent 'anti-ageing' chocolate|url=http://www.independent.co.uk/life-style/food-and-drink/news/esthechoc-scientists-invent-antiageing-chocolate-10060075.html}}</ref><ref>{{cite web|title=Startup Alkahest inks a $50M deal for anti-aging R&D|url=http://www.fiercebiotech.com/story/startup-alkahest-inks-50m-deal-anti-aging-rd/2015-03-04}}</ref> In 2015 a new class of drugs [[senolytics]] was announced (currently in pre-clinical development) designed specifically to combat the underlying biological causes of frailty.<ref>{{cite web|title=New "Senolytic" Drugs Can Dramatically Increase Healthy Lifespan|url=http://io9.com/new-senolytic-drugs-can-dramatically-increase-healthy-1690827868}}</ref> ==Philanthropy== The 'loss of youth' or ageing process is responsible for increasing the risk of individuals to many diseases including [[Cancer]], [[Parkinsons]], [[alzheimers]], and others. As a result in recent years many high net worth individuals such as [[Peter Thiel]],<ref>{{cite news|title=Billionaire Peter Thiel embarks on anti-aging crusade|url=http://venturebeat.com/2014/10/08/billionaire-peter-thiel-may-want-to-live-forever/}}</ref> [[Aubrey de Grey]],<ref>{{cite news|title=terview with Aubrey de Grey, PhD|url=http://www.lef.org/magazine/2013/7/Interview-with-Aubrey-de-Grey-PhD/Page-01}}</ref> [[Larry Ellison]], [[Sergey Brin]], [[Dmitry Itskov]], [[Paul Glenn]],<ref>{{cite web|title=These Tech Billionaires Are Determined to Buy Their Way Out of Death |url=http://www.businessinsider.com/tech-billionaires-immortality-2013-8?IR=T}}</ref> and [[Mark Zuckerberg]] <ref>{{cite news|last1=http://phys.org/news/2013-02-zuckerberg-brin-life.html|url=http://phys.org/news/2013-02-zuckerberg-brin-life.html}}</ref> have donated large amounts of their money towards initiatives towards scientific research into the ageing process itself or therapies to slow or reverse the ageing process. This would allow humans to extend their youth or maintain youth indefinitely. ==See also== *[[Ageless]] *[[DNA damage theory of aging]] *[[Dorian Gray]] *[[Elixir of life]] *[[Fountain of Youth]] *[[Indefinite lifespan]] *[[Immortality]] *[[Peter Pan]] ==References== {{Reflist|refs= <ref name="Siegel">{{cite web |author=Lee J. Siegel |title=ARE TELOMERES THE KEY TO AGING AND CANCER? |url=http://learn.genetics.utah.edu/content/begin/traits/telomeres/ }}</ref> <ref name="Damm">{{cite journal |author=Klaus Damm |title=A highly selective telomerase inhibitor limiting human cancer cell proliferation |url=http://www.nature.com/emboj/journal/v20/n24/full/7594184a.html |journal=The EMBO Journal |year=2001 |doi=10.1093/emboj/20.24.6958 |volume=20 |issue=24}}</ref> <ref name="Hornsby">{{cite journal |author=Peter J. Hornsby |title=Telomerase and the aging process |year=2007 |journal=PubMed |doi=10.1016/j.exger.2007.03.007 |pmc=1933587 |pmid=17482404 |volume=42 |issue=7 |pages=575–81}}</ref> }} {{Longevity}} {{DEFAULTSORT:Eternal Youth}} [[Category:Death]] [[Category:Fictional superhuman features or abilities]] [[Category:Life extension]] [[Category:Mythological powers]] [[Category:Youth]] [[Category:Ageing]]'