WHAT’S the point of old men? We women have had our postmenopausal existence justified, in evolutionary terms, by the grandmother hypothesis. But the same cannot be said for men. The mystery is why they live long past their physical prime, with muscles turning to flab and potency waning.

In How Men Age, we have an answer. Biological anthropologist Richard Bribiescas covers some interesting uncharted territory. This is not a mere description of ageing. Instead, by considering male ageing in the light of natural selection, it aims to answer big questions including why men’s lifespans are shorter than women’s, why baldness, prostate disease and erectile dysfunction are so prevalent, and how humans as a species have benefited from men’s tendency to run to fat.

From an evolutionary perspective, nothing matters more than sex. And as far as men are concerned, nothing influences sexual power more than testosterone. It increases libido, promotes muscle growth and encourages risk-taking behaviour – all of which help attract a mate. But testosterone peaks in early adulthood, so that men are past their physical prime by the age of 30. It’s tempting to see it as all downhill from there. But with wit and insight, Bribiescas shows convincingly that’s not the case.

He points out that testosterone has a dark side – it can increase a man’s metabolic rate and suppress the immune system. In other words, there’s a trade-off, or as Bribiescas puts it: “macho makes you sick”. High levels of the hormone early in life help explain why men don’t live as long as women and why they are prone to prostate cancer later on. So waning testosterone can be seen as a positive development. It may make older men less physically competitive against younger ones, but men can produce offspring throughout their lives and, argues Bribiescas, as they age they develop new reproductive strategies to achieve this.

For a start, although they may lack raw strength, their experience and guile often make them better providers than their younger counterparts. Bribiescas has done fieldwork with the Ache people of Paraguay, and points to research showing that men’s hunting success peaks in their 40s, long after their testosterone levels peak.

What’s more, older men tend to become more nurturing. As testosterone decreases, a man’s girth increases, and the metabolic changes associated with growing adiposity promote care of offspring. Bribiescas calls this the “pudgy dad hypothesis”, and argues that it has implications for the evolution of our species as a whole.

Humans live far longer than other primates. For longevity to evolve, natural selection must favour long-lived individuals. Older women cannot reproduce, so they are out of the running. But if, throughout human history, pudgy older men have been fathering children, then they will have passed on genes associated with longevity to both daughters and sons.

Old men, therefore, could be the reason we all live so long. It would appear there is some point to them after all.

This article appeared in print under the headline “Golden oldies”

IT COULD be the biggest killer you’ve never heard of: the weakening and loss of muscle that happens as we get older.

Muscle loss is no longer seen as just a side effect of disease and frailty – it’s also a prime cause. As well as contributing to falls, muscle loss has serious knock-on effects on metabolism (see “Life-saving muscle”). In future, muscle-boosting drugs could aid those unable to maintain muscle mass through exercise such as weight training. Although researchers stress this isn’t about bodybuilding, but keeping muscles in your limbs at a healthy level.

Muscle loss, also known as sarcopenia, is increasingly being seen as an important facet of ageing, according to several speakers at a held in Basel, Switzerland, last month. “Treatments will eventually get into the market,” said Dan Perry of the patient lobby group .

However, the mechanisms behind muscle ageing are still poorly understood – although new research suggests it involves damage from free radicals.

Mice that have been genetically modified to produce fewer free radicals in their mitochondria are known to . So a team led by Andrew Marks at Columbia University in New York investigated how this affected the ageing of their muscle tissue.

They found that a key player is calcium, the release of which triggers our muscles to contract. The molecule responsible for this release – ryanodine receptor 1 – is damaged by free radicals, and as the rodents age, calcium begins to leak out when it shouldn’t, weakening muscle fibres.

The modified mice experienced less free radical damage to the ryanodine receptor 1. They also had stronger muscles, and, in old age, chose to run on their exercise wheels more than unmodified mice – by about an extra kilometre a day ().

“It helps point to the role that mitochondria play in the muscle ageing process,” says Daniel Moore of the University of Toronto, Canada.

Marks has founded a firm called to develop several compounds aimed at preventing calcium leakage, which are in early-stage clinical trials.

“People think of muscle as the body’s mover, but it’s really a huge metabolic organ”

Other drugs are in development that combat sarcopenia in different ways. Muscle fibres are in a constant state of turnover, being simultaneously broken down and regrown, so any compound that tips the balance towards growth could help build muscle mass.

One class of drug includes the compound , which works by blocking a signalling pathway targeted by an inhibitor of muscle growth called myostatin. Others work by .

“There’s a lot of interest in trying to come up with something for sarcopenia because at the moment there’s no treatment,” says Marks.

Indeed, it’s only within the last six months that US researchers have even agreed on how to define the condition – essential before a drug treatment can be approved. The US National Institutes of ��ҹ����1000���� .

“We have come a long way in how to approach this,” says of the University of Maryland, who was involved in the defining process.

In the meantime, there is already a natural way to boost muscle: exercise. “The mitochondrial function of lifelong exercisers is like that of someone half their age,” says Moore. “One of the best anti-ageing pills is to stay active.”

This article appeared in print under the headline “Beefing up can keep you healthy”