Timeline of senescence research
This page is a timeline of senescence research, including major theories, breakthroughs and organizations. "Senescence" here refers to "Ageing" rather than the phenomena of cellular senescence, which is a change in cell state associated with ageing, cancer prevention, wound healing, regeneration and embryonic/placenta development.
|Ancient Greece||Early speculations on aging are focussed on the bodily humoral imbalance and on the gradual loss of inner heat.|
|Middle Age/Renaissance||Rejuvenating or stopping the aging process is a major concern in this period.|
|Renaissance–18th century||Some themes around which aging and senescence research revolves around are the idea that senescence is itself an illness, the image of the aged body as a lamp in which life-fuel has run out, the character alterations of elders, and the attempt to prolong life through specific diet or by substituting damaged body parts.|
|Late 19th–20th century||Starting from the so-called "fin-de-siècle" period, scientific optimism flourishes, and life-extensionism represents the most radical form of the trend. Life expectancy starts to rise in the Western world.|
|20th century|| Senescence research focuses on four major directions: cellular theories, immune-metabolic models, evolutionary explanations and molecular biology-based approaches.
Modern anti-aging organizations merge and their proliferation multiplies toward the 2000s.
|Year/period||Type of Event||Event||Location|
|c. 99 BC – c. 55 BC||Theory||Roman poet and philosopher Lucretius argues that aging and death are beneficial because they make room for the next generation. This view will persist among biologists well into the 20th century.|
|5th century||Theory||Early formulations, described by Hippocrates' system of four humours, theorize old age as a consequence of the gradual consumption of the innate heat with the inevitable loss of body moisture.||Greece|
|1825||Development||Benjamin Gompertz proposes an exponential increase in death rates with age, giving birth to what later will be called The Gompertz-Makeham law |
|1891||Theory||August Weismann proposes the first formal programmed aging theory as an evolutionary explanation of aging driven by group selection. His argument is that aging evolved to the advantage of the species (e.g., by replacing worn out individuals with younger ones), not the individual.|
|1908||Theory||Max Rubner describes his rate-of-living theory, which proposes that a slow metabolism increases an animal's longevity. It states that fast basal metabolic rate corresponds to short maximum life span.|
|1913||Organization||The Life Extension Institute is inaugurated as a longevity research center, with US president William Howard Taft as chairman.||U.S.A.|
|1928||Theory||Raymond Pearl describes the Rate Of Living Hypothesis as an expansion of the earlier theory by Max Rubner. It states that organisms with a high metabolic rate have shorter lives.|
|1934||Discovery||Mary Crowell and Clive McCay of Cornell University discover that calorie restriction can extend lifespan twofold in rats.|
|1945–1949||Development||The advent of molecular biology changes the theoretical perception of aging dramatically, as the precise molecular structure of proteins and genetic material becomes known.||U.S.A.|
|1950s||Theory||Denham Harman presents his free radical theory of aging, which states that organisms age over time due to the accumulation of damage from free radicals in the body.|
|1952||Theory||Peter Medawar formulates the first modern theory of mammal aging, known as mutation accumulation, whereby the mechanism of action involves random, detrimental germline mutations of a kind that happen to show their effect only late in life.|
|1957||Theory||George C. Williams proposes the today called antagonistic pleiotropy hypothesis (AP) for the evolution of aging. It occurs when one gene controls for more than one phenotypic trait where at least one of these is beneficial to the organism's fitness and at least one is detrimental, thus accumulating damage.|
|1958||Theory||G. Failla and Leó Szilárd propose the somatic mutation theory, which suggests that aging is caused by random DNA damage in somatic cells and that the extent of damage is enhanced by radiation.|
|1961||Theory||American anatomist Leonard Hayflick demonstrates that a population of normal human fetal cells in a cell culture will divide between 40 and 60 times before entering a senescence phase. This process will be known later as the Hayflick limit.||Philadelphia|
|1965–1969||Discovery||The strong effect of age on DNA methylation levels is discovered, thus rendering it an accurate biological clock in humans and chimpanzees.|
|1967||Theory||C. Alexander sets the grounds of the DNA damage theory of aging by suggesting that DNA damage, as distinct from mutation, is the primary cause of aging. This theory becomes stronger through further experimental support during the following decades.|
|1969||Book||American physician Roy Walford publishes The Immunologic Theory of Aging, contributing to the basis for many current ideas about immunological aging.|
|1974||Organization||The National Institute on Aging (NIA) is formed as a division of the U.S. National Institutes of Health (NIH), with the purpose of conducting research on aging process and age-related diseases and disseminating information on health and research advances, among other aims.||Baltimore, U.S.A.|
|1975–1984||Discovery||Elizabeth Blackburn discovers the unusual nature of telomeres, with their simple repeated DNA sequences composing chromosome ends. Some years later Blackburn, Carol Greider and Jack Szostak discover how chromosomes are protected by telomeres and the enzyme telomerase, for which they receive the 2009 Nobel Prize in Physiology or Medicine. Further experiments establish the role of telomere shortening in cellular aging and telomerase reactivation in cell immortalization.|
|1977||Theory||Thomas Kirkwood proposes the third mainstream theory of ageing, the disposable soma, which states that organisms only have a limited amount of energy that has to be divided between reproductive activities and the maintenance of the non-reproductive aspects of the organism.|
|1990||Organization||The Gerontology Research Group (GRG) is founded as a global group of researchers in various fields that verifies and tracks supercentenarians. It also aims to further gerontology research with a goal of reversing or slowing aging.||Los Angeles, (UCLA)|
|1990-1995||Development||The term negligible senescence is first used by professor Caleb Finch to describe organisms such as lobsters and hydras, which do not show symptoms of aging.|
|1991||Theory||Leonid A. Gavrilov and Natalia S. Gavrilova apply the principles of reliability theory to human biology, proposing a reliabity theory of aging which is based on the premise that humans are born in a highly defective state. According to the model, this is then made worse by environmental and mutational damage, and survival of the organism depends on redundancy.|
|1993||Discovery||Dr. Cynthia Kenyon discovers that a single-gene mutation (Daf-2) can double the lifespan of nematode Caenorhabditis elegans and that this can be reversed by a second mutation in daf-16m.|
|1994||Book||Leonard Hayflick publishes How and Why we Age.|
|1995||Development||Detection of senescent cells using a cytochemical assay is first described.|
|2003||Organization||Dr. Aubrey de Grey and David Gobel form the Methuselah Foundation, which gives financial grants to anti-aging research projects.||Springfield, Virginia, U.S.A.|
|2009||Organization||De Grey and several others found the SENS Research Foundation with aims at conducting research into aging and funding other anti-aging research projects at various universities.||Mountain View, California, U.S.A|
|2010||Achievement||Harvard scientists reverse aging process in mice through reactivation of telomerase.||U.S.A.|
|2013||Organization||Google announces Calico, with the purpose of harnessing new technologies to increase scientific understanding of the biology of aging.||San Francisco, U.S.A|
|2016||Discovery||Scientists demonstrate for the first time that mitochondria are major triggers of cell aging.||Newcastle upon Tyne, UK (Newcastle University)|
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