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Monday 6 August 2007 11pm-midnight


Why is our time limited? And does it have to be? Could our age-old dream of immortality ever be possible? In episode two, Michio Kaku explores these questions and meets some of the key people involved in the cutting-edge research into ageing. He travels to the amazing Methuselah tree, which is almost 5000 years old and still producing new pine cones. He discovers that time

WATCH VIDEO CLIPS



An experiment which proves time does get faster as you get older

How genetic research into ageing has produced extraordinary possibilities for extending life


does get faster as you get older and, under hypnosis, he goes in search of his lost time, stored as memories. But it only proves that lost time is really gone forever.
We are incredible machines for living - but if we're programmed to live, are we also programmed to die? As we grow, our cells divide into a complex colony of three trillion individual cells in our bodies. Sir Paul Nurse has spent a lifetime studying cells to search for the most basic process of life - the secret of cell division. We discover that cells seem to be potentially immortal. They continue to divide again and again perfectly. Even our own bodies are replaced through our lives - most of our cells are replaced in a roughly seven-year cycle. Yet we know that we age and that time wreaks changes on our bodies.

This episode reveals the biological changes in our cells that make our skin wrinkle and our bones become brittle. This new understanding is beginning to reveal the process of time in our bodies and, through this, scientists are now looking at ways of slowing or even stopping time. Scientists in California are studying sea urchins for clues as they not only live longer than ever thought before but they appear to show no sign of ageing. Genetic manipulation is extending the lives of mice. And a British scientist is now suggesting that the pace of advance is so fast that the first immortals are already living today; that before our children have reached the end of their natural lives, the technology to stop and even reverse ageing will exist. But what will that mean for our essential humanity?



//////////////////////OLD AGE IS A DRAG


//////////////////////OUR ALLOTTED TIME -MAYBE 122 YRS


//////////////////Cambrian explosion changed ocean chemistry
Mud stirred up by sea-floor animals may have stoked global sulphate levels.

Eric Hand


Cambrian species may have driven up the concentration of gypsum in the Earth's crust.Wikimedia Commons
A little more than 500 million years ago, something put the evolutionary pedal to the metal, and the stately, subdued pace of animal life on Earth revved up. Alongside this spurt in speciation — known as the Cambrian explosion — came a jump in the concentration of sulphate in the world's oceans.

"It hasn't been clear why," says Don Canfield of the University of Southern Denmark in Odense. But Canfield and his collaborator, James Farquhar of the University of Maryland in College Park, have a theory to explain it. It's a murky story with a moral: never underestimate the power of a scum-sucking, ocean-bottom worm.

Photosynthetic plants have had their own ancient and idiosyncratic effect on carbon and oxygen cycles. But in a study published this week in the Proceedings of the National Academy of Sciences1, Canfield and Farquhar attribute the rise in sulphate to the onset of bioturbidity — the burrowing, sluicing, pumping and mixing caused by masses of worms, clams, crustaceans and other animals that began to appear around this time in Earth's history.

The planet has long been seen as a driver of evolution. But this, say Canfield and Farquhar, is an important example of how animals, too, can create a global geochemical signal that, in turn, twists evolution's corkscrew. "The Cambrian explosion needs to be viewed as not the consequence of geochemical perturbations, but the cause of them," says Nick Butterfield of the University of Cambridge, UK, who was not affiliated with the study.

Mixing it up

Before these sea-floor animals began their steady churn, sulphate — arriving in seas in the run-off from rivers — would largely be turned into hydrogen sulphide by bacteria living in the ocean floor. The sulphide would then be converted to pyrite (FeS2), which, once buried, removes the sulphate from the system. Once bioturbation turned on, however, oxygen in the deep ocean could mix more freely with the sediments, allowing bacteria and other processes to recycle pyrite and turn it back to sulphate. This excess sulphate would have reached a saturation point, giving rise to the formation of gypsum deposits — a mineral that, along with sulphate levels, also happened to rise in the rock record around this time.

The researchers roughly sketched changes in ocean sulphate concentrations through time by directly analysing tiny amounts of brine trapped in salt crystals. But these samples are few and far between, so to get a more complete timeline, the team analysed sulphide and sulphate isotopes in thousands of ancient sedimentary rock samples. This analysis doesn't track sulphate concentration changes directly, but shows how much of the sulphur ended up in pyrite versus gypsum. Finally, the researchers built a simple model for the effects of bioturbation and found that its output — both in the timing and the magnitude of the sulphate signals — matched what they were seeing in the data.

Butterfield notes that the work underscores the importance of marine animals. On land, animals (except for modern humans) have had only a muted effect on global geochemical systems, perched as they are at the top of food chains. But in seas, where animals make up a significant fraction of the biomass, they can pack a geochemical punch. Butterfield says that the work of Canfield and Farquhar could lead to a questioning of the conventional wisdom that global increases in atmospheric oxygen were the original cause of the Cambrian animal explosion. Extra oxygen would have been needed, for example, to favour the higher metabolism of multicellular animals such as gigantic dragonflies. In a recent editorial in the journal Geobiology, Butterfield proposed that global increases in oxygen might have instead occurred as a result of oceanic phytoplankton that belched oxygen as a by-product into the atmosphere — a scenario in which, again, animals would be the cause rather than the consequence of a change in planetary geochemistry2.

Too little, too late?

Biogeochemist Tim Lyons, of the University of California at Riverside, says that as a first-order solution, the theory proposed by Canfield and Farquhar works well. But he points out that data gaps still need to be filled and specific problems must be worked out — for instance, explaining gypsum deposits that are far more ancient than the Cambrian era. Also, he says, the deep burrowing animals that would have done the most to mix oxygen into the sea floor didn't come along until some time after the Cambrian explosion — so the sudden rise in sulphate concentrations precisely at the Cambrian boundary is difficult to explain.



Lyons thinks that increases in atmospheric oxygen could be at least partly responsible for the rise in oceanic sulphate without the invocation of animals. More oxygen, percolating from the atmosphere into the ocean, would on its own encourage the recycling of pyrite into sulphates. And higher oxygen levels in deep seas might encourage existing animals to migrate into them, where they could become the sea-floor blenders that Canfield and Farquhar propose.

So are animals the cause or the consequence of these epochal changes to the oxygen and sulphur cycles? Similar to the question of the chicken and egg, the answer might not be one or the other. "These things go hand in hand," Lyons says. "Both are important, and one goes with the other."

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