The average lifespan of humans has gone from 36 to around 80 years. Today the world’s oldest living human is nearly 120 years old (Lucille Randon was born in February 1904 in France).
The world record for the oldest human being ever is currently held by Jeanne Calment, another Frenchwoman, at 122 years old (born. in 1875 and died. in 1997).
Several factors influence the average duration of human life, including the usual suspects: genetics, environment, and lifestyle.
By the turn of the 20th century, economic and environmental changes were in full swing.
The 1900s brought improved food availability, better access to clean water, and better living conditions.
Scientific understanding of infectious diseases has taken huge leaps, and this, in turn, positively impacted healthcare.
Better healthcare meant lower risk for infant mortality, improved chances of surviving childhood, and better awareness of how to avoid communicable diseases.
Needless to say, longevity and the study of human lifespan and whether or not it is controlled by systemic factors became a study of interest to scientists.
Long-living individuals like nonagenarians, centenarians, semi-supercentenarians, and supercentenarians were studied and interviewed to find a possible connecting pattern.
While the results showed that there were no remarkable similarities in education, income or profession amongst the subjects, they did share significant similarities in lifestyle habits.
For example, many of them were non-smokers, were not obese, and had better mechanisms for coping with stress.
Interestingly, most of them were women.
Due to their healthy habits, older adults were less prone to high blood pressure, heart disease, cancer, and diabetes compared to their peers.
Is longevity genetic?
The positive health effects of these older adults extended to their first-degree relatives (siblings and children).
Children and siblings of long-living adults are more likely to live long lives themselves, showing that there is a genetic link in this mechanism.
People whose parents are centenarian are less likely to have an age-related diseases that is common among adults who are more than 70 years of age.
Longevity, like other bodily phenomenons, tends to run in families and this led scientists to examine which genes were likely responsible for this effect.
What are the longevity genes?
Although still a developing science, around 25% of the variation in human life span is found to be determined by genetics.
The genes that are associated with longevity are APOE, FOXO3, and CETP.
Variations in these genes are found in all the subjects with extraordinary longevity.
Scientists have conducted whole genome sequencing in supercentenarians to try and identify these gene variations.
Results of these studies show an increased disease risk in individuals with an average life span.
Lifestyle versus genetics
Despite these results scientist hypothesise that the first 70-80 years in the lives of supercentenarians are more likely due to healthy lifestyle habits than genetics.
Nutritious and wholesome diets, low alcohol intake, not smoking, and staying physically active seem to have a higher weightage when it comes to longevity.
A healthy lifestyle is shown to have reduced the risk of such individuals for typical age related ailments like heart disease and high blood pressure.
In fact many nonagenarians and centenarians live a high quality life with no age-related disease until the fag end of their lives.
How do genes impact longevity?
The genes that have been shown to have the maximum impact on longevity are related to maintenance and optimal functioning of the cells.
Critical cell functions like maintenance of telomeres, DNA repair, and protection from free radicals have a high impact on longevity.
Further genes that are implicated in risk of heart disease, the main cause of mortality in older people, also influence longevity.
These genes are involved in vital organ systems like the cardiovascular and immune system and processes like inflammation and maintenance of blood lipid levels.
These genes are also implicated in the risk of stroke and insulin resistance.
Longevity in the human population
Regions like Okinawa (Japan), Ikaria (Greece), and Sardinia (Italy) are places where many people live to see their nineties or older.
Naturally, these are places of interest to scientists studying longevity.
Common themes in these countries are that still follow a very traditional way of life without major influences from the Western world.
Further studies are needed to understand the genetic and environmental factors influencing these populations.
Summary
Several factors influence the average duration of human life, including genetics, environment, and lifestyle. Commonly implicated genes associated with longevity are APOE, FOXO3, and CETP. Nutrition, low alcohol intake, not smoking, and staying physically active seem to have a higher weightage when it comes to longevity. Further studies are needed to understand the genetic and environmental factors influencing these populations.
