Disrupted DNA in the "power packs" of cells may explain why women tend to live longer than men, research suggests.
Mutations in the mitochondria - rod-like bodies in cells that generate energy - cause men to die early, scientists believe.
The evidence emerged from studies of male and female fruit flies.
Scientists believe that 'natural selection' helps women achieve greater life expectancy
Like humans and other animals, the flies only inherit mitochondrial genes from their mothers.
This could account for the fact that mitochondrial mutations are more likely to affect men, say scientists.
How about these 'anti-ageing' treatments? Scroll down (PICTURES)
"While children receive copies of most of their genes from both their mothers and fathers, they only receive mitochondrial genes from their mothers," said lead scientist Dr Damian Dowling, from Monash University in Australia.
"This means that evolution's quality control process, known as natural selection, only screens the quality of mitochondrial genes in mothers.
"If a mitochondrial mutation occurs that harms fathers, but has no effect on mothers, this mutation will slip through the gaze of natural selection, unnoticed. Over thousands of generations, many such mutations have accumulated that harm only males, while leaving females unscathed."
SEE ALSO:
The study appears in the latest issue of the journal Current Biology. It found that genetic variation across mitochondria was a reliable predictor of life expectancy in male, but not female, flies.
Most inherited DNA, comprising the majority of genes, is wrapped up in the nucleus at a cell's heart.
The mitochondria have their own separate DNA, which is also passed down to offspring - but only by mothers.
In earlier research, Dr Dowling's team linked the maternal inheritance of mitochondria to male infertility.
"Together, our research shows that the mitochondria are hotspots for mutations affecting male health," said the doctor.
"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."