Read more: Extreme survival: The toughest life forms on Earth
Death has no sting for the jellyfish that has no age, and it’s a remote prospect for a lot of other organisms too
Of all the limitations on Earth there is one that no life can escape: death. But some living things manage to outsmart their fate for longer than others.
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For reasons that aren’t well understood, animals rarely make it to their 100th birthday. But, as ever, there are exceptions. The oldest living animal yet discovered is a marine clam of the species Arctica islandica caught off the coast of Iceland. According to some estimates, this individual, which has been named Ming, is around 400 years old. But as-yet-unpublished research led by Paul Butler, an animal growth specialist at Bangor University, UK, suggests it may be older still.
No one knows how these clams manage to live so much longer than other animals. What is known is that at some point in their lifespan, their , making it far from certain whether they experience ageing in the sense that we know it.
“As the clams get older their death rate drops, so they may not even experience ageing as we know it”
Plants get around the ageing problem by allowing the cells in the oldest parts of the organism to die while continuing to produce new sections. The most extreme examples are so-called clonal trees, which reproduce by sprouting genetically identical colonies over vast areas, all sharing the same root system. A stand of clonal quaking aspens, Populus tremuloides, in Utah may be one of the oldest such examples. While the existing trees seem to be no more than 130 years old, parts of the roots have been dated to around 80,000 years old.
The oldest individual tree ever recorded was a bristlecone pine, or Pinus longaeva. Named Prometheus, it was around 5000 years old when it was felled in 1964. Again, though, the oldest parts of the tree were long dead, and the living part only tens or hundreds of years old.
Probably the oldest living things on the planet are bacteria found in the permafrost of Siberia, Canada and the Antarctic. These Actinobacteria are thought to have been alive for around 500,000 years (). This could be because they have a very slow metabolism and super-efficient DNA-repair mechanisms that help them to cope with a serious lack of food while allowing them to live for a very, very long time.
But perhaps nothing can beat the “immortal jellyfish”, Turritopsis nutricula, which can revert to an immature stage after becoming sexually mature and can go on ageing and “unageing” indefinitely – in theory. After all, there is nothing stopping it getting eaten before it reaches a ripe old age, and no way of measuring that age anyway.
