Editing Life extension (section)

==Average life expectancy and lifespan==
{{Main|Senescence}}
During the process of [[aging]], an organism accumulates damage to its [[macromolecule]]s, [[cell (biology)|cells]], [[biological tissue|tissues]], and [[organ (anatomy)|organs]]. Specifically, aging is characterized as and thought to be caused by "genomic instability, telomere attrition, epigenetic alterations, loss of [[proteostasis]], deregulated nutrient sensing, mitochondrial dysfunction, [[cellular senescence]], stem cell exhaustion, and altered intercellular communication."<ref>{{cite journal | vauthors = López-Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G | title = The hallmarks of aging | journal = Cell | volume = 153 | issue = 6 | pages = 1194–1217 | date = June 2013 | pmid = 23746838 | pmc = 3836174 | doi = 10.1016/j.cell.2013.05.039 }}</ref> [[Oxidation]] damage to cellular contents caused by [[free radicals]] is believed to contribute to aging as well.<ref>Halliwell B, Gutteridge JMC (2007). Free Radicals in Biology and Medicine. Oxford University Press, USA, {{ISBN|019856869X}}, {{ISBN|978-0198568698}}</ref><ref>{{cite journal | vauthors = Holmes GE, Bernstein C, Bernstein H | title = Oxidative and other DNA damages as the basis of aging: a review | journal = Mutation Research | volume = 275 | issue = 3–6 | pages = 305–315 | date = September 1992 | pmid = 1383772 | doi = 10.1016/0921-8734(92)90034-M }}</ref>

The longest documented human lifespan is 122 years 164 days, the case of [[Jeanne Calment]], who according to records was born in 1875 and died in 1997, whereas the maximum lifespan of a [[wildtype]] mouse, commonly used as a model in research on aging, is about three years.<ref>{{cite web|url=http://www.informatics.jax.org/mgihome/other/mouse_facts1.shtml|title=Mouse Facts|publisher=informatics.jax.org}}</ref> Genetic differences between humans and mice that may account for these different aging rates include differences in efficiency of [[DNA repair]], [[antioxidant]] defenses, [[energy metabolism]], [[proteostasis]] maintenance, and recycling mechanisms such as [[autophagy]].<ref>{{cite web | vauthors =  Pedro de Magalhães J | date = 2014 |url= http://www.senescence.info/causes_of_aging.html|title=What Causes Aging? Damage-Based Theories of Aging}}</ref>

The average life expectancy in a population is lowered by [[infant mortality|infant]] and [[child mortality]], which are frequently linked to infectious diseases or nutrition problems. Later in life, vulnerability to [[accident]]s and age-related [[chronic disease]] such as [[cancer]] or [[cardiovascular disease]] play an increasing role in mortality. Extension of life expectancy and lifespan can often be achieved by access to improved medical care, [[vaccinations]], good [[diet (nutrition)|diet]], [[exercise]], and avoidance of hazards such as [[tobacco smoking|smoking]].

[[Maximum lifespan]] is determined by the rate of aging for a species inherent in its [[gene]]s and by environmental factors. Widely recognized methods of extending maximum lifespan in model organisms such as [[nematode]]s, fruit flies, and mice include [[caloric restriction]], [[gene manipulation]], and administration of pharmaceuticals.<ref>{{cite journal | vauthors = Verdaguer E, Junyent F, Folch J, Beas-Zarate C, Auladell C, Pallàs M, Camins A | title = Aging biology: a new frontier for drug discovery | journal = Expert Opinion on Drug Discovery | volume = 7 | issue = 3 | pages = 217–229 | date = March 2012 | pmid = 22468953 | doi = 10.1517/17460441.2012.660144 | s2cid = 24617426 }}</ref> Another technique uses evolutionary pressures such as breeding from only older members or altering levels of extrinsic mortality.<ref>{{cite journal | vauthors = Rauser CL, Mueller LD, Rose MR | title = The evolution of late life | journal = Ageing Research Reviews | volume = 5 | issue = 1 | pages = 14–32 | date = February 2006 | pmid = 16085467 | doi = 10.1016/j.arr.2005.06.003 | s2cid = 29623681 }}</ref><ref>{{cite journal | vauthors = Stearns SC, Ackermann M, Doebeli M, Kaiser M | title = Experimental evolution of aging, growth, and reproduction in fruitflies | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 97 | issue = 7 | pages = 3309–3313 | date = March 2000 | pmid = 10716732 | pmc = 16235 | doi = 10.1073/pnas.060289597 | doi-access = free | bibcode = 2000PNAS...97.3309S }}</ref>
Some animals such as [[hydra (genus)|hydra]], [[planarian| planarian flatworms]], and certain [[sponges]], [[corals]], and [[jellyfish]] do not die of old age and exhibit potential immortality.<ref>{{cite journal | vauthors = Newmark PA, Sánchez Alvarado A | title = Not your father's planarian: a classic model enters the era of functional genomics | journal = Nature Reviews. Genetics | volume = 3 | issue = 3 | pages = 210–219 | date = March 2002 | pmid = 11972158 | doi = 10.1038/nrg759 | s2cid = 28379017 }}</ref><ref>{{cite journal|year=1992 |title=Bi-directional conversion in ''Turritopsis nutricula'' (Hydrozoa) |journal=Scientia Marina |volume=56 |issue=2–3 |pages=137–140 |url=http://evolucionuader.yolasite.com/resources/Bavestrello%20et%20al%201992.pdf | vauthors = Bavestrello G, Sommer C, Sarà M |url-status=dead |archive-url=https://web.archive.org/web/20150626120819/http://evolucionuader.yolasite.com/resources/Bavestrello%20et%20al%201992.pdf |archive-date=2015-06-26 }}</ref><ref>{{cite journal | vauthors = Martínez DE | title = Mortality patterns suggest lack of senescence in hydra | journal = Experimental Gerontology | volume = 33 | issue = 3 | pages = 217–225 | date = May 1998 | pmid = 9615920 | doi = 10.1016/S0531-5565(97)00113-7 | s2cid = 2009972 | citeseerx = 10.1.1.500.9508 }}</ref><ref>{{cite journal | vauthors = Petralia RS, Mattson MP, Yao PJ | title = Aging and longevity in the simplest animals and the quest for immortality | journal = Ageing Research Reviews | volume = 16 | pages = 66–82 | date = July 2014 | pmid = 24910306 | pmc = 4133289 | doi = 10.1016/j.arr.2014.05.003 }}</ref>