The average life expectancy for a woman is greater than for a man in almost every country in the world and it does not just occur in humans. A similar pattern can be found in many other species too! There have been many theories hypothesised as being the reason behind this difference including more active female immune functioning, protective effect of oestrogen, compensatory effects of the second X chromosome, reduction in the activity of growth hormone and the influence of oxidative stress but the majority of them are based on minimal evidence.
The most recent reasoning behind the differing lifespan of men and women which is ~4-5 years on average is based on mitochondrial DNA mutations. Mitochondria are vital to our existence because they are the ‘power house’ cells of the body, responsible for providing us with energy for everything from breathing to muscle contraction.
Mitochondrial DNA is inherited from our mother’s. Mitochondria tend to harbour mutations which are more harmful to men than women. This is because mutations harmful to females tend to be ‘weeded out’ in the process of natural selection as it is females who pass mitochondrial DNA to their offspring, leaving men more vulnerable to harmful mutations not dealt with by natural selection.
Whether this is irrevocably true remains to be seen, but there certainly is a biological reason behind the increased longevity of female life.
A few interesting statistics:
- The oldest recorded person ever to have lived was a French lady called Jeanne Calment who lived to the grand old age of 122 years and 164 days old!
- The average life expectancy in the UK is 78.1 years for men and 82.1 years for women.
- Around the world there are 9 times as many women over the age of 100 than there are men.
Austad SN, Why Women Live Longer Than Men: Sex Differences In Longevity, Gender Medicine, 2006, 3(2): 79-92.
Eskes T, Haanen C, Why Do Women Live Longer Than Men? European Journal of Obstetrics and Gynaecology and Reproductive Biology, 2007, 133(2): 126-33.