[Part 1 is being translated]
II. Sex hastens death, geneticist says
May 24, 1997
BY ALISON MOTLUK New Scientist
Although being female never has been easy, there always has been one clear advantage: longer life. But now a British geneticist is claiming that males, not females, are programmed to live longer.
It is the relentless pursuit of sex that sends them to an early grave, he says.
In almost every species where one sex lives longer -- from worms to cats to humans -- females enjoy the longer life span. Scientists have assumed that this is due to a superior "constitutional endowment" -- meaning that females are simply designed to live longer.
But work with worms has persuaded David Gems, a geneticist at University College in London, that scientists may be wrong: Males have the greater underlying longevity, he contends in research he described last week.
He reached this conclusion over the past year while studying the nematode worm, Caenorhabditis elegans. In this population there are very few males; most worms are hermaphrodites.
But the hermaphrodites are "essentially females capable of making a small number of sperm for self-fertilization," Gems said in a recent interview. So, for the purposes of his research he treated them as female.
Gems saw that when he put male worms together they died in about 10 days, several days sooner than when they were left with females. But when he isolated individual male worms, they lived for 20 days. That surpassed the average female life span of 16 days. Isolating female worms had no effect on their life spans.
Gems attributed the premature male deaths to too much activity: They were perpetually defending territory and competing for mates.
To test the idea further, Gems measured the life spans of worms with genetic mutations that made them less sexually active. These laid-back males lived even longer -- for 30 days. The same mutations did nothing to lengthen females' lives.
"Life span is limited by the rate of movement," Gems told a meeting of the Zoological Society of London. Exceeding a threshold of activity, he suggests, shortens a worm's life.
Gems says that there is plenty of evidence that males of other species would live longer than females if it weren't for sexual activity.
If male marsupial mice are castrated they can live for years, Gems says. Otherwise, they die in just a few sex-crazed weeks. "They spend 5 to 11 hours a day copulating," he says.
Among humans, a study of 319 eunuchs in 1969 showed that
their median life span was 13.5 years longer than intact males.