A group of scientists believe they have discovered a clue to why women tend to live longer than men by studying fruit flies.
Published in Current Biology, the study focuses on mutations in mitochondrial DNA – the power source of cells.
Mitochondria are inherited only from mothers, never from fathers, so there is no way to weed out mutations that damage a male’s prospects.
But one ageing expert said there were many factors that explained the gender difference in life expectancy.
And females outlive males in many other species.
Scientists believe they have discovered a clue to why women tend to live longer than men by studying fruit flies
In the research, experts from Australia’s Monash University and the UK’s Lancaster University analyzed the mitochondria of 13 different groups of male and female fruit flies.
Mitochondria, which exist in almost all animal cells, convert food into the energy that powers the body.
Dr. Damian Dowling, of Monash University who was one of the researchers, said the results point to numerous mutations within mitochondrial DNA that affect how long males live, and the speed at which they age.
“Intriguingly, these same mutations have no effects on patterns of ageing in females,” he said.
“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 ageing across the animal kingdom.”
They suggest this is because there is no evolutionary reason for the faults that affect males to be picked up – because mitochondria are passed down by females.
Dr. Damian Dowling added: “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.”
New details have been revealed after DNA analysis was performed on what could be described as the world’s oldest murder case of Otzi the “Iceman”, whose 5,300-year-old body was discovered frozen in the Italian Alps in 1991.
Otzi’s full genome has now been reported in Nature Communications.
DNA analysis reveals that Otzi had brown eyes, “O” blood type, was lactose intolerant, and was predisposed to heart disease.
They also show him to be the first documented case of infection by a Lyme disease bacterium.
Analysis of series of anomalies in the Iceman’s DNA also revealed him to be more closely related to modern inhabitants of Corsica and Sardinia than to populations in the Alps, where he was unearthed.
The study reveals the fuller genetic picture as laid out in the nuclei of Otzi’s cells.
This nuclear DNA is both rarer and typically less well-preserved than the DNA within mitochondria, the cell’s “power plants”, which also contain DNA.
Otzi’s mitochondrial DNA had already revealed some hints of his origins when it was fully sequenced in 2008.
Albert Zink, from the Eurac Institute for Mummies and the Iceman in Bolzano, Italy, said the nuclear DNA study was a great leap forward in one of the most widely studied specimens in science.
“We’ve been studying the Iceman for 20 years. We know so many things about him – where he lived, how he died – but very little was known about his genetics, the genetic information he was carrying around,” Albert Zink said.
A reconstruction shows how Otzi the Iceman may have looked like before an arrow felled him
Otzi was carrying around a “haplotype” that showed his ancestors most likely migrated from the Middle East as the practice of formal agriculture became more widespread.
It is probably this period of transition to an agrarian society that explains Otzi’s lactose intolerance.
Prof. Albert Zink said that next-generation “whole-genome” sequencing techniques made the analysis possible.
“Whole-genome sequencing allows you to sequence the whole DNA out of one sample; that wasn’t possible before in the same way.
“This was really exciting and I think it’s just the start for a longer study on this level. We still would like to learn more from this data – we’ve only just started to analyse it.”