Is longevity primarily determined by genetics?
When I was young, my grandfather used to tell me he was ‘nearly 100 years old’. He made this claim when he was only in his 80s, but this year, as he approaches his 100th birthday, his statement is finally true.
Whilst the average life expectancy in many developed countries is around 80 years old, some people, like my grandfather, live to their late 90s or even over 100 years. Some individuals have surpassed even those landmarks - the oldest person who ever lived died at 122 years old!
Whilst death is inevitable, longevity varies drastically between individuals. What is the secret to a long life? Is our longevity already encoded in our DNA or is it determined by our lifestyle? We asked 11 experts in ageing, cell biology and genetics ‘Is longevity primarily determined by genetics?’, here is what we found out…
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Is longevity primarily determined by genetics?
Longevity in comparison to what?
Experts had two different interpretations of the question:
1) ‘Is the longevity of humans as compared to other species primarily determined genetics?’
2) ‘Is the longevity of some individual humans as compared to other humans primarily determined by genetics?’
Genetics determines cross-species life-spans
Different animal species have very different life spans. The Greenland shark is able to live to be 400 years old, whilst some species of Mayfly only live for 5 minutes. The reason for these differences is genetics.
Professor David Gems, an expert in ageing from University College London, says “the question could mean: are the upper limits of longevity in humans as a species primarily determined by genetics, in which case the answer is ‘near certain’. For example, the maximum lifespan of human beings is approximately twice that of our closest relatives among the higher primates, such as chimpanzees and gorillas.”
Lifestyle more important than genes across humans
Dr Gems says “If one takes [the question] to mean: are the differences in lifespan between individual people primarily determined by genetics, then the answer is ‘extremely unlikely’”. Most of the experts agreed with Dr Gems. Whilst genetics plays a role in longevity, it is not the primary determining factor.
Professor Dame Janet Thornton, an expert in anti-ageing and cell biology and previous director of the European Bioinformatics Institute says that “Genetics accounts for less than 30% of the effect - but it is true that longevity tends to run in families - ie some families have many very old people!”.
It can be difficult to determine if the existence of families with many very old people is due to genetics or environment, as often family members adopt similar diets and lifestyles. Studying the DNA of these long-lived people could tell us more. Professor Ken Parkinson, an expert in anti-aging and oncology from Queen Mary University London says “many groups are trying to understand this by sequencing the DNA of centenarians and supercentenarians and performing genome-wide analysis”
The lifestyle effect on longevity is clearly apparent when we look at how average life spans have increased over hundreds of years due to increased accessibility of clean water, food and medical care. Counter-intuitively, it has been shown that restricting calorie intake could be linked to longevity in humans. Another lifestyle factor is exercise. Even light exercise for 15 minutes a day has been shown to increase life expectancies by around 3 years.
Individual longevity between humans is affected by genetics, but not primarily. Professor Lorna Harries, an expert in genetics and cell biology from Exeter University summarises “Genetics can set you up for a long life, but you then need to do the right things to realise that.”
Differences in longevity between humans is not primarily determined by genetics. Regular exercise and a healthy diet may be the ‘secret’ to longevity.
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