Longevity

Longevity may refer to especially long-lived members of a population, whereas life expectancy is defined statistically as the average number of years remaining at a given age.

For example, a population's life expectancy at birth is the same as the average age at death for all people born in the same year (in the case of cohorts).

There are difficulties in authenticating the longest human life span, owing to inaccurate or incomplete birth statistics.

Significant factors in life expectancy include gender, genetics, access to health care, hygiene, diet and nutrition, exercise, lifestyle, and crime rates.

[10] Twin studies have estimated that approximately 20-30% of the variation in human lifespan can be related to genetics, with the rest due to individual behaviors and environmental factors which can be modified.

[15] These findings suggest that elevated PARP gene expression contributes to the longevity of centenarians, consistent with the DNA damage theory of aging.

[16] In July 2020, scientists used public biological data on 1.75 m people with known lifespans overall and identified 10 genomic loci which appear to intrinsically influence healthspan, lifespan, and longevity – of which half have not been reported previously at genome-wide significance and most being associated with cardiovascular disease – and identified haem metabolism as a promising candidate for further research within the field.

[19][20][21] A 2012 study found that even modest amounts of leisure time physical exercise can extend life expectancy by as much as 4.5 years.

Despite this, there are several examples of pre-20th-century individuals attaining lifespans of 85 years or greater, including John Adams, Cato the Elder, Thomas Hobbes, Christopher Polhem, and Michelangelo.

[30] This reflects overall poorer health and greater prevalence of heart disease, obesity, diabetes, and cancer among black American men.

Theories for this include smaller bodies that place lesser strain on the heart (women have lower rates of cardiovascular disease) and a reduced tendency to engage in physically dangerous activities.

It suggests that while biological complexity increases individual lifespan, it is counteracted in nature since the survivability of the overall species may be hindered when it results in a prolonged development process, which is an evolutionarily vulnerable state.

[38] According to the antagonistic pleiotropy hypothesis, one of the reasons biological immortality is so rare is that certain categories of gene expression that are beneficial in youth become deleterious at an older age.

[47] Longevity in other animals can shed light on the determinants of life expectancy in humans, especially when found in related mammals.

[48] Similarly, a chameleon, Furcifer labordi, is the current record holder for shortest lifespan among tetrapods, with only 4–5 months to live.