Eternal Youth
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.
Fountain of Youth
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.
Elixir of Life
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
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).
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