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. Eternal youth is common in mythology, and is a popular theme in fiction.
The Fountain of Youth is a legendary spring that supposedly restores the youth of anyone who drinks or bathes in its waters. Tales of such a fountain have been recounted across the world for thousands of years, appearing in writings by Herodotus, the Alexander romance, and the stories of Prester John. Stories of similar waters were also evidently prominent among the indigenous peoples of the Caribbean during the Age of Exploration, who spoke of the restorative powers of the water in the mythical land of Bimini.
The legend became particularly prominent in the 16th century, when it became attached to the Spanish explorer Juan Ponce de León, first Governor of Puerto Rico. According to an apocryphal combination of New World and Eurasian elements, Ponce de León was searching for the Fountain of Youth when he traveled to what is now Florida in 1513.
The elixir of life, also known as elixir of immortality and sometimes equated with the philosopher's stone, is a legendary/mythical potion, or drink, that when drank from a certain cup, at a certain time, grants the drinker eternal life and/or eternal youth. Many alchemists pursued it. The elixir of life was also said to be able to create life. It is related to the myths of Thoth and Hermes Trismegistus, both of whom in various tales are said to have drunk "the white drops" (liquid gold) and thus achieved immortality. It is mentioned in one of the Nag Hammadi texts.
Immortality is the ability to live forever, or eternal life. Biological forms have inherent limitations which medical interventions or engineering may or may not be able to overcome. Natural selection has developed potential biological immortality in at least one species, the jellyfish Turritopsis nutricula.
Certain scientists, futurists, and philosophers, have theorized about the immortality of the human body, and advocate that human immortality is achievable in the first few decades of the 21st century, while other advocates believe that life extension is a more achievable goal in the short term, with immortality awaiting further research breakthroughs into an indefinite future. Aubrey de Grey, a researcher who has developed a series of biomedical rejuvenation strategies to reverse human aging (called SENS), believes that his proposed plan for ending aging may be implementable in two or three decades. The absence of aging would provide humans with biological immortality, but not invulnerability to death by physical trauma. What form an unending human life would take, or whether an immaterial soul exists and possesses immortality, has been a major point of focus of religion, as well as the subject of speculation, fantasy, and debate.
In religious contexts, immortality is often stated to be among the promises by God (or other deities) to human beings who show goodness or else follow divine law (cf. resurrection).
The Epic of Gilgamesh, one of the first literary works, dating back at least to the 22nd century BC, is primarily a quest of a hero seeking to become immortal.
Wittgenstein, in a notably non-theological interpretation of eternal life, writes in the Tractatus that, "If we take eternity to mean not infinite temporal duration but timelessness, then eternal life belongs to those who live in the present."
DNA damage theory of aging
The DNA damage theory of aging proposes that aging is a consequence of unrepaired accumulation of naturally occurring DNA damages. Damage in this context is a DNA alteration that has an abnormal structure. Although both mitochondrial and nuclear DNA damage can contribute to aging, nuclear DNA is the main subject of this analysis. Nuclear DNA damage can contribute to aging either indirectly (by increasing apoptosis or cellular senescence) or directly (by increasing cell dysfunction).
In humans and other mammals, DNA damage occurs frequently and DNA repair processes have evolved to compensate. In estimates made for mice, on average approximately 1,500 to 7,000 DNA lesions occur per hour in each mouse cell, or about 36,000 to 160,000 per cell per day (Vilenchik & Knudson 2000). In any cell some DNA damage may remain despite the action of repair processes. The accumulation of unrepaired DNA damage is more prevalent in certain types of cells, particularly in non-replicating or slowly replicating cells, such as cells in the brain, skeletal and cardiac muscle.
Maximum life span
Maximum life span refers to a measure of the maximum amount of time one or more members of a population has been observed to survive between birth and death. The term can also denote an estimate of the maximum amount of time that a member of a given species could survive between life and death, provided circumstances that are optimal to their longevity.
Most living species have at least one upper limit on the number of times cells can divide. For humans, this is called the Hayflick limit, although number of cell divisions does not strictly control lifespan (non-dividing cells and dividing cells lived over 120 years in the oldest known human).