Longevity

Longevity is about life expectancy, and as a civilization advances with medical technology and quality of life, longevity improves. The range for the evolution of homo sapiens is around 30 (Type 0.1) for a fully grown adult to over 5000 years (Type IV), making one effectively immortal.

A reduction in current lifestyle diseases, such as obesity, diabetes, hypertension, and heart disease, will improve longevity. Michio Kaku argues that genetic engineering, nanotechnology and future breakthroughs will accelerate the rate of life expectancy indefinitely. Already genetic engineering has allowed the life expectancy of certain primates to be doubled, and for human skin cells in labs to divide and live indefinitely without becoming cancerous.

Gerontology
Gerontology is the science of physiological aging and death. Senescence is the condition or process of deterioration with age, or the loss of a cell's power of division and growth.

There is no single medical reason for aging. The twice Nobel laureate Dr. Linus Pauling asserted: "Death is unnatural. Theoretically, man is quite immortal. His body tissues replace themselves. He is a self-repairing machine. And yet, he gets old and dies, and the reasons for this are still a mystery".

However, there exist within humans three primary "clocks of aging":

Wear and tear
The body deteriorates from accident or hard usage after a number of years, depending on lifestyle or bad luck.

Cell division
Young human cells can divide only a limited number of times (roughly 50 generations) before all their descendants age and die. Adult cells divide even fewer times (about 20) before death ensues. Animals with longer lifespans have the longest-lived cells. 50 divisions would mean a life expectancy of 70 to 80 years, whereas a tortoise has 90-125 divisions with a life expectancy of 150 to 200 years. Aging thus appears to be a built-in genetic limitation to cellular regeneration and growth.

Hormonal
The third clock of aging is hormonal in nature, found in human endocrine glands. Most people die because of a failure of one of the two major body systems: the cardiovascular or the immune systems. Death occurs from heart stoppage or from an inability of the blood vessels to deliver oxygen and nutrients to vital organs, or from a failure of the body’s immune system to ward off an attack of invading microorganisms. The thyroid gland produces thyroxine which is the master rate-controlling hormone. The pituitary may release some kind of blocking hormone (a death hormone) that prevents cells from using thyroxine, leading to increased destructive oxidation, chromosomal mutations and heart tissue dysfunction.

Another endocrine gland, the thymus, has been implicated in aging. The level of thymosin (the secretion of the thymus gland decreases with age, and the failure rate of the human immune system rises markedly. Lymphocytes, our "white cells," become increasingly incompetent. They fail to rid the body of hostile pathogens and mistakenly attack the body’s own cells as if they were foreign invaders. As a result, older organisms are vastly more susceptible to a wide range of potentially lethal diseases.

Defusing the aging time bomb
Three clocks of aging are simultaneously ticking against us. Defusing each stage increases our life expectancy dramatically:

Stage 1: Hormonal imbalances occur which cause the cardiovascular and immune systems ultimately to fail. This is the body’s primary self-destruct mechanism. Typical life expectancy: 30-80 years.

Stage 2: The cellular aging program causes body cells to cease dividing after a fixed number of generations. This is the body’s secondary self-destruct mechanism. Typical life expectancy: 110-120 years.

Stage 3: Wear and tear on body structures. Irreversible genetic deterioration or severe accidental trauma eventually cause senescence and death. This is the body’s last line of defense against immortality. Typical life expectancy: 1000 years.

Regenerative medicine
This is bioengineering to replace or regenerate cells, tissues or organs. Tissues and organs may be grown in the laboratory when the body cannot be stimulated to heal itself. Methods include the injection of stem cells or progenitor cells via cell therapies; infused cell immunomodulation therapy; and transplantation of in vitro grown organs and tissues via tissue engineering.

Strategies for engineered negligible senescence (SENS) proposes that rejuvenation may be obtained by removing aging damage via the use of stem cells and tissue engineering, telomere-lengthening machinery, immunotherapeutic clearance, and other novel ideas.

Anti-aging drugs
The enzyme telomerase could be used to counter the process of telomere shortening. Telomeres form the ends of human chromosomes. Telomeres shorten with each round of cell division and this mechanism limits proliferation of human cells to a finite number of cell divisions by inducing replicative senescence.

Autophagy
Autophagy, meaning "self-devouring", is the natural mechanism of a cell that removes unnecessary or dysfunctional components, thereby allowing recycling of cellular parts and homeostasis of cells. Autophagy is seen as an adaptive response to stress, promoting survival of the cell, but in other cases it promotes cell death and morbidity. Insufficient autophagy is one of the main reasons for the accumulation of damaged cells and aging.

Autophagy plays an important role in cancer – both in protecting against cancer as well as potentially contributing to the growth of cancer. It acts as both a tumor suppressor and a factor in tumor cell survival. Recent research has shown, however, that autophagy is more likely to be used as a tumor suppressor according to several models. Autophagy is also linked to inflammation, Parkinson’s disease and diabetes, so using drugs to ensure the correct functioning of autophagy will play a large role in disease reduction and anti-aging.

Nanotechnology
Nanomedicine could give rise to life extension through the repair of many processes thought to be responsible for aging. Moleculartronic computers could operate within cells and repairs could be automated or directed remotely. Raymond Kurzweil stated in his book The Singularity Is Near that advanced medical nanorobotics could completely remedy the effects of aging by 2030.

Cloning and body part replacement
Therapeutic cloning and stem cell research could provide a way to generate cells, body parts, or even entire bodies (reproductive cloning) that would be genetically identical to a patient.

The use of human stem cells is controversial. Opponents' objections generally are based on interpretations of religious teachings or ethical considerations. Proponents of stem cell research point out that cells are routinely formed and destroyed in a variety of contexts.

The controversies over cloning are similar, similar to those found in teleportation. Successful cloning resulting in a sapient being would conclude that a human being is no more than the sum of his or her quantum parts, and directly confront a wealth of spiritual beliefs.

Another method of body part replacement involves progressively replacing neurons with transistors, altering a conscious mind from a biological brain to a non-biological computer system or computational device. The structure of a brain is scanned and a software model of it is made, so when run on appropriate hardware it will behave in the same way as the original brain. Where or not this is a true continuation of a person's consciousness is open to debate.

Cyborgs
Replacement of biological (susceptible to diseases) organs with mechanical ones will extend life.

Cryonics
Cryonics is the low-temperature freezing of a human corpse, with the hope that resuscitation may be possible in the future. Some may even willingly freeze themselves while alive with the dream they may awake to a utopian future.

Genetic editing
Genome editing to correct genetic mutations is a strategy to prevent aging. A 2020 study identified 10 genomes which influence health-span, lifespan, and longevity. Genes involved in metabolizing iron likely increase healthy years of life in humans. Yeast cells age in two distinct ways, and a biomolecular mechanism can fix which process dominates during aging and genetically engineer a novel aging route with substantially extended lifespan.

In The Selfish Gene, Richard Dawkins describes a life extension that involves "fooling genes" into thinking the body is young. We possess more lethal genes that activate in later life than in early life. Therefore, to extend life, we should be able to prevent these genes from switching on, and we should be able to do so by "identifying changes in the internal chemical environment of a body that take place during aging... and by simulating the superficial chemical properties of a young body".

Mind uploading
With advances in VR, it would be possible to upload your mind into a virchworld, thereby attaining a dubious form of immortality. This could be done when one is close to biological death, or even willingly in order to escape the woes of real life. There would be laws, ethics and living wills associated with this practice.

Senotherapy
This uses therapeutic agents and strategies to target cellular senescence, an altered cell state associated with ageing and age-related diseases.


 * Geroprotectors are prevent or reverse the senescent state by preventing triggers of cellular senescence, such as DNA damage, oxidative stress, proteotoxic stress, telomere shortening, melatonin, carnosine, metformin, nicotinamide mononucleotide (NMN) and delta sleep-inducing peptide.


 * SASP inhibitors – agents interfering with pro-inflammatory Senescence Associated Secretory Phenotype (SASP) production


 * Senolytics are small molecules that induce death of senescent cells and improve health in humans. Senolytics are used to delay, prevent, alleviate, or reverse age-related diseases.


 * Senomorphics – small molecules that suppress senescent phenotypes without killing cells

Young blood injection
The injection of blood products from young donors give the benefits of a longer life, darker hair, better memory, better sleep, curing heart diseases, diabetes and Alzheimer's disease.