Could it be possible that another life form in the universe has a lifespan measured in many hundreds or thousands of our years?
Herman D鈥橦ondt
Sydney, Australia
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We don鈥檛 even need to look elsewhere, as there are quite a few species on Earth with very long lifespans.
The oldest living individual land animal is a Seychelles tortoise, with an estimated age of 192 years. He is still going strong and may well live beyond 200 years. In the ocean, the longest-lived vertebrate is the Greenland shark, with a lifespan of several centuries. By carbon dating the inside of its eye, one individual has been measured at 392 years old, though it might have been about a century older or younger.
In the plant world, lifespans are much longer. Trees routinely live for centuries or millennia. A bristlecone pine in Nevada was around 4900 years old when it was felled. A quaking aspen in Utah is estimated to be around 15,000 years old. This tree is actually a forest of clones, interconnected by the root system and covering about 43 hectares. As such, it is also the world鈥檚 largest 鈥渢ree鈥�.
Living bacteria have been found inside 2-billion-year-old volcanic rocks from South Africa
Digging deeper in the tree of life, in northern Canada, living bacteria around half a million years old have been found in permafrost. In 2020, living microbes were found in suspended animation in submarine sediments dated from 4 million to 100 million years old. Living bacteria have been found in 2-billion-year-old volcanic rocks from South Africa. While they look much more primitive than modern bacteria, that doesn鈥檛 mean they date from the time of the formation of the rocks 鈥� they are old, but not that old.
Finally, some species, such as hydras, don鈥檛 grow old. Some hydrozoans can repeatedly revert from the adult stage back to the juvenile polyp stage. As a result, they may live forever, but nobody has observed them for long enough to know.
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