Wednesday, October 31, 2007

Could Ming the mollusc hold the secret to Nature's greatest mystery?

Growing old and and dying is inevitable yet meet the mighty Ming who has been around for 405 years

Growing old and dying is as inevitable as paying taxes.

However much we may moan and rage or smear ourselves with youth-preserving potions, we'll be lucky to blow out the candles on our 90th birthday cake.

For one of our fellow creatures, however, nine decades is scarcely the length of its childhood. The ocean quahog (a type of deep-sea clam) can, it seems, chug on and on and on for several centuries.

In fact, one specimen that has been dredged from the Atlantic sea-floor off the coast of Iceland has just set a record as the oldest living creature on the planet.

Meet the mighty Ming, whom scientists say has been around for a grand total of 405 years.

And no, he wasn't named after the former Lib Dem leader. This chap was given his title in honour of the Imperial dynasty that ruled China at the time of his birth — at the start of the 17th century.

Record-breaker: Ming was 405 years old when he died

Having seen off Queen Elizabeth I, the English Civil War, the entire Enlightenment, the Industrial Revolution, two World Wars and the advent of reality TV, Ming was caught last year when scientists from the University of Bangor were dredging the seabed near Iceland as part of a study into climate change.

He was taken back to the laboratory where tests were conducted on his shell to determine his age. As the quahog's shell grows at different rates at different times of the year, it consists of hundreds of distinct layers that can be counted like rings in a tree trunk to give its age.

Researcher Alan Wanamaker found the first layers of Ming's shell were made more than four centuries ago.

That made him 32 years older than the previous oldest recorded creature (another quahog) whose shell is now in a German museum.

But that is not the only reason why scientists have got so excited about the discovery. For although Ming may be small — he'd fit in the palm of your hand — he could hold a mighty secret.

Creatures like him may show us why some species are able to cheat ageing and death for so much longer than others.

And perhaps — just perhaps — he can show us that our own lifespan is not so inevitable after all.

That's the hope of charity Help the Aged, which has given the marine biologists from Bangor University £40,000 to investigate why this animal lives so long.

For if we discover how a living creature can live into its fifth century, then we might be able to do something to extend human longevity as well, or at least make old age a little more palatable.

That is the theory, anyway. In the meantime, we still have to get to grips with just why there are such fantastic differences in the lifespans of different species.

Some Galapagos tortoises, for instance, have been recorded to reach nearly 200 years.

And bowhead whales have been found recently with antique harpoons embedded in their skulls dating from the 1790s.

Unless these were a freak, this means that in the sea today there may be large, intelligent animals that pre-date the invention of the railway engine.

Other Methuselahs include orange roughy, a Pacific fish increasingly popular as food.

These cold-water fish can live to more than 150 years old, meaning that your dinner could date back to a time when Queen Victoria was still middle-aged.

But how do these creatures live so long?

In fact, while the lifespans of different species may seem random, there is a pattern.

Generally, big creatures live longer than small ones — and this goes for plants as well as animals.

At one end of the scale are mice and shrews, which live just a couple of years, while at the other are large animals like rhinos, hippos, giant tortoises, lions and elephants, which have life expectancies measured in decades — or even centuries.

But there are some interesting anomalies.

Humans, for instance, live longer than is to be expected for our size — the record stands at 122 years, achieved by the Frenchwoman Jeanne Calment, who personally knew Vincent van Gogh and died in 1997.

We certainly do better than our closest relatives, bonobos and chimpanzees, which are lucky to make 70, even in pampered captivity.

Horses and cattle, however, do badly despite their large size, while some parrots live for 70 years or more despite being small.

And fish and molluscs can, as we have seen, survive for centuries.

So, what determines how long a species can live? Biologists used to think that animals (and plants) die because, like machines, they simply wear out.

But unlike machines, animals' bodies are equipped with efficient repair mechanisms.

The question is: why do these fail and what determines how old we are when they do?

The evolutionary theory of ageing, now widely accepted, states simply that animal lifespans reflect the amount of time an organism can expect to survive in the wild before being killed by predators, cold, disease or starvation.

This explains why big animals tend to live longer than small ones — they are simply less likely to be eaten or die of starvation, so their bodies have evolved to age and develop more slowly, as time is not of the essence for them.

The theory also explains the anomalies: bats and birds have long lifespans because they can fly, making them far safer from predators than comparably sized ground-living creatures.

Tortoises, too, live a long time because they are armour-plated — as are clams.

Few things eat whales, or large crocodiles, and it takes a long time for a big animal to die of starvation.

Mice, on the other hand, are so vulnerable to being eaten or squashed that their bodies are designed for speed, not endurance.

They have rapid, high-octane metabolisms that help them do just one thing — make lots of babies, very quickly, before getting eaten.

However, these fast, superheated metabolisms take a toll on their bodies.

Flooded with sex hormones and corrosive sugars, small mammals soon succumb to cancers and other ageing diseases, even if protected in the lab.

But is it possible to use this knowledge to increase human longevity?

Could we tweak our metabolisms in some way so that we could live as long as Ming the clam?

The answer is almost certainly yes, but not any time soon.

Some scientists believe it may be possible to fool our bodies into ticking over more slowly by going on a very low-calorie diet, living in a state of near-starvation.

But in the future, our best hope probably lies with genetic manipulation, combined with drug therapies to defuse the genetic timebombs left in our DNA by our savannah ancestry.

That's all a long way off.

But the good news for our generation is that while the human lifespan is probably unassailable for now, human life expectancy is not.

In other words, the numbers of us who can expect to live close to the current maximum possible age for humans is growing all the time.

A girl, born to affluent middleclass parents in the world's richer countries, now has a life expectancy of more than 85 (80 for boys) and this will increase further.

This alone may cause us problems, as the ratio of pensioners to workers changes dramatically.

What would happen in a world where people lived to be 405 can only be guessed at.

As for Ming? Well, he's already paying the price of fame.

By the time the mollusc had been inspected in the lab, and his record confirmed, he'd passed over to that great ocean bed in the sky.

No one can say it wasn't an impressive innings.

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