This timeline lists notable events in the history of research into senescence or biological aging, including the research and development of life extension methods, brain aging delay methods and rejuvenation.
People have long been interested in making their lives longer and healthier. The most ancient Egyptian, Indian and Chinese books contain reasoning about aging. Ancient Egyptians used garlic in large quantities to extend their lifespan. Hippocrates (), in his Aphorisms, and Aristotle (384–322 BCE), in On youth and old age, expressed their opinions about reasons for old age and gave advice about lifestyle. Medieval Persian physician Ibn Sina ( – 1037), known in the West as Avicenna, summarized the achievements of earlier generations about this issue.
Background Descriptions of rejuvenation and immortality remedies are often found in the writings of alchemists. But all those remedies did not allow even alchemists themselves to live longer than a hundred years.
Though the average lifespan of people through the past millennia increased significantly, maximum lifespan almost did not change - even in ancient times there were fairly well and unbiasedly documented cases when some people lived for more than a hundred years (for example, Terentia who lived 103 or 104 years). While among the billions of people of the modern world, there is only one case of life over 120 years (Jeanne Calment, 122 years). The super-long lives of people that are mentioned in ancient books, apparently, are highly exaggerated, since archaeological data show that even the oldest of the ancient people lived no more than modern supercentenarians. In some cases the exaggeration, possibly, is not intentional but occurs due to errors in translation between languages and synchronization of chronological systems. The species limit of human life is estimated by scientists at 125–127 years, and even in the most ideal conditions a person will not live longer due to aging of the body.
Some scientists believe that, even if medicine learns how to treat all major diseases, that will increase the average lifespan of people in developed countries by only about 10 years. For example, biogerontologist Leonard Hayflick stated that the natural average lifespan for humans is 92 years. Meanwhile, the life expectancy for Japanese already now is more than 84 years, and for Monaco it is reported to be more than 89 years. It may not be possible to achieve further increases without development of new biomedical technologies and approaches. Searches of various equivalents of the elixir of youth happened yet in ancient times: people hoped to find a miraculous remedy in faraway territories, tried to use magic and alchemy. Scientific and technological attempts began at the end of the 19th century. For their intended purpose, all of them turned out to be inefficient at best, sometimes led to premature death, but they had many useful and sometimes unexpected consequences.
Timeline
Ancient 350 BCE — The Greek philosopher Aristotle, arguably the first philosopher to make a serious attempt to scientifically explain aging, proposes his thesis on aging. He suggests that aging is a process by which human and animal bodies, which are naturally hot and wet, gradually become dry and cold, and theorizes that more moisture delays aging. 259–210 BCE — years of life of the Chinese emperor Qin Shi Huang, who united China under his rule. All his life he persistently searched for an elixir of youth and died trying, presumably taking "pills of immortality", containing mercury. 156–87 BCE — years of life of the Chinese emperor Wu of Han, who persistently tried to find a way to achieve immortality, mainly by means of magic. He used services of various magicians. But Wu of Han was not a naive person – he thoroughly rechecked their abilities and if he identified the person as a quack, he executed him. 63 BC–14 CE — years of life of Caesar Augustus, the first Roman emperor, who is considered one of the most effective leaders of the Ancient Rome. For him an eternal youth was an obsession. In particular, contrary to the Roman tradition to create statues as realistic as possible, he always ordered to portray himself young. There are many of his "youthful" statues but researchers still do not know how he looked in old age. 3rd–17th century — the period of alchemy. There are several directions in alchemy, and it was distributed over a huge territory. But almost everywhere, in one form or another, there was the concept of a "philosopher's stone" – some substance that is able to turn other metals into gold, and when taken internally in small doses, heal all diseases, rejuvenate an old body and even give biological immortality. Alternatively, there were attempts to prepare "pills of immortality". During centuries alchemy gradually transformed to chemistry, in parallel giving birth to many adjacent sciences or enriching them. It is worth noticing the direction of iatrochemistry – a rational direction of alchemy with the main goal of preparing medicinal products. The pioneers of iatrochemistry were Paracelsus (1493–1541), Jan Baptist van Helmont (1580–1644) and Franciscus Sylvius (1614–1672). The converging field of alchemy was transformed into pharmacy. 1513 — searching for the Fountain of Youth is in popular culture thought to be one of the purposes of the expedition of the Spanish conquistador Juan Ponce de León, which lead to the discovery of Florida – however, there is no contemporary evidence of this, and this purpose is considered a myth by historians. 1550 — a Venetian nobleman Luigi Cornaro published the book The Art of Living Long, describing the style of life for the achievement of longevity. The book was translated into many languages. The English version of the book till the 19th century went through more than 50 editions. The main idea of the book: in order to live many years, you need to live in moderation, eat simply and little. In his youth Cornaro led a free and immoderate life, as a result by the age of 35 he had many health problems. But by changing his lifestyle he was able to live to 98 (1467–1566). (Though it is possible that he exaggerated his age by about 17 years to give his recommendations more weight.)
19th century to WWII From the end of the 19th century, systematic scientific and technical studies began on the processes of slowing down aging and possible rejuvenation. The period of world history between the two world wars is a very complicated, difficult and ambiguous time of world history. In many spheres of life, there were ideas that were radical-bold, but not always intelligent, ethical and moral from the point of view of modern knowledge, foundations and norms. This also affected the aging research, the spirit of which corresponded to the spirit of that time: attempting bold experiments, often on people, intensively implementing in practice treatments that we may now consider ridiculous. Those attempts had both bad and good consequences. But those researches were already scientific. As it often happens in science, it is often difficult to establish priority considering, who was the first person beginning to use one or another approach. Usually the first experiments are done by enthusiasts and have doubtful positive effects. Some researchers work in parallel. Then at some moment the persons emerge who developed the approaches and made them public.
1825 The first publication of the Gompertz–Makeham law of mortality that in the simplest form is: p = a + bx. According to the law, the probability of death p is defined as the sum of age-independent component a and the component depending on age bx which with age increases exponentially. If we place organisms in an absolutely protected environment and in this way make the first component negligible, the probability of death will be completely defined by the second component which actually describes the probability to die from aging. 1860s Alfred Russel Wallace writes down what is probably the first evolutionary theory of aging. In notes written sometime between 1865 and 1870, he proposed a wear and tear theory of aging, suggesting that older animals which continue to consume resources, competing with their offspring in an environment with limited food, were disfavored by natural selection. Therefore, he suggested that aging was an evolved trait which allowed an organism's descendants to thrive. 1882 August Weismann puts forward the wear and tear theory of aging independently of Wallace. 1889 Rejuvenation experiment conducted on himself by the French doctor Charles-Édouard Brown-Séquard. He made himself a few subcutaneous injections from the testicles of young dogs and guinea pigs and claimed that the injections were accompanied by significant and long pain, but then he observed an improvement of the physical condition of the organism and increase of mental activity. Experiments of other scientists, at first, produced the same results but later it became clear that the period of reinforced activity is followed by a period of decline. At the moment of the experiment Charles-Édouard Brown-Séquard was 72 years old. After the experiment he claimed he felt as if he became younger by 30 years. However, 5 years later he died. But other doctors picked up this method and it created the foundation for the development of hormone replacement therapy. 1903 Ilya Mechnikov coined the term "gerontology". The term originates from the Greek γέρων, geron, "old man" and -λογία, -logia, "study of". From 1897 to 1916 Mechnikov conducted many studies on the effect of acidified dairy products (especially Bulgarian yogurt and bacteria used for its production) on longevity and quality of life in old age. He developed the concept of probiotic diet that promotes long healthy life. In 1908 Mechnikov received the Nobel Prize for his work on immunology (adjacent area of his research). Adhering to his diet, Mechnikov lived a very long life compared to his short-lived relatives. 1914 Dr. Frank Lydston from Chicago performed human testis transplants on several patients, including himself, and said that there were some rejuvenating consequences (such as returning his gray hair to its original color and improving of sexual performance). These works remained little known. The work of Leo L. Stanley, that he began to do since 1919, received much more prominence . 1915–1917 Experiments to find out the effects of food restriction on the life duration of rats, conducted by Thomas Osborne. Apparently, these were the first systematic experiments in this direction. These experiments remained little known. The method was popularized by Clive McCay in 1934–1935 . 1910s–1930s Austrian physiologist Eugen Steinach was trying to achieve rejuvenation effects by means of different surgical operations such as partial vasectomy for men, ligation of fallopian tubes for women, transplantation of testicles, etc. And although later these operations were found to be ineffective, they allowed the researchers to recognize the role of the sexual glands and sexual hormones in the formation of the first and secondary sex characteristics, enriched physiology, laid the foundation for the science of sexology, formed the basis for sex reassignment surgeries. From 1921 to 1938, Eugen Steinach was nominated for the Nobel Prize many times (according to various sources, from 6 to 11 times), but never received it.