Women outlive men by about five to six years but why? By age 85 there are roughly six women to every four men and by age 100 the ratio is more than two to one.
Now scientists think they may have found the answer in the aptly named "Mother's Curse."
Published in Current Biology, research led by Dr Damian Dowling and Florencia Camus of Monash University in Australia, together with Dr David Clancy of Lancaster University in the UK shows that a set of DNA inherited only from the mother can be harmful to males and speed up male aging.
Dr Dowling said the results point to numerous mutations within mitochondrial DNA that affect how long males live, and the speed at which they age.
He said: "Intriguingly, these same mutations have no effects on patterns of aging in females. They only affect males.
"All animals possess mitochondria, and the tendency for females to outlive males is common to many different species. Our results therefore suggest that the mitochondrial mutations we have uncovered will generally cause faster male aging across the animal kingdom."
Dr David Clancy from the Faculty of Health and Medicine at Lancaster University said this is a major advance in biology.
"We show that Mother's Curse is much broader in its effects on male life history than previously envisaged, resulting in the build-up of mutations that cause males to age faster, and live shorter lives than females.
"These findings …offer a new and compelling explanation to one of life's greatest puzzles -- why the female of many species, including humans, live longer than the males. "
Mitochondrial DNA, which is found in every cell in the human body except red blood cells, converts the energy of food molecules into energy.
It is inherited through the mother only so any harmful mutations which affect only males will have no impact on females, who will continue to pass on mitochondrial DNA to their sons.
Earlier, the team of researchers published the first evidence proving that mitochondrial DNA harbour mutations which interfere with male fertility, but have no harmful effects on female fertility.
This latest research also implicates the Mother's Curse as a key player in evolution, since both male reproduction and male aging are affected by mitochondrial DNA passed on by the mother.
Dr Dowling said: "Together, our research shows that the mitochondria are hotspots for mutations affecting male health. What we seek to do now is investigate the genetic mechanisms that males might arm themselves with to nullify the effects of these harmful mutations and remain healthy."
- M. Florencia Camus, David J. Clancy, Damian K. Dowling. Mitochondria, Maternal Inheritance, and Male Aging. Current Biology, 2012; DOI: 10.1016/j.cub.2012.07.018
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