The oldest living thing on Earth

Jun 13: Mayflies live a day, humans live a century, if we’re lucky, but what is the oldest living organism on the planet? For scientists, accurately proving the age of any long-lived species is a hard task.

Under the boughs of a 300-year-old sweet chestnut tree in the Royal Botanic Gardens in Kew, Tony Kirkham, head of the arboretum, confirms that trees are capable of outliving animals.

Proving this can involve some traditional detective work, as he explains: “First of all we can look at previous records, to find out if a tree was growing there at a set date. Then we look at paintings and artwork, to look to see if that tree was present. And old ordinance survey maps quite clearly show ancient trees, especially important ones.”

A well-known way of measuring the age of a tree is by counting the rings in its trunk: one ring per year of growth. It’s a process known as dendrochronology and only works for certain types of tree that have an annual growth spurt.

The obvious problem is that counting rings normally involves cutting down the tree.

Arboriculturalists get around this by using an increment borer, a drill that allows them to take out a core, and count the rings without fatally damaging the tree.

It’s a delicate art, and, Tony says, back in the 1960s, one scientist’s drill broke off inside the bristlecone pine tree he was sampling.

The kit is expensive, and to help him recover the lost instrument, a forester helpfully cut down the tree. Once felled, the tree could be easily aged, and was found to be 5000 years old.

“It was terrible but so much science came out of that opportunity, and since then, we’ve found trees that are as old, if not older,” admits Tony.

A team of researchers in the US keeps a list, called the Old List, of officially dated ancient trees.

They’ve found a sacred fig tree in Sri Lanka that is at least 2,222 years old.

There’s a Patagonian cypress tree in Chile which, at 3,627 years old, is as old as Stonehenge.

A Great Basin bristlecone pine in California’s White Mountains named Methuselah comes in at 4,850 years old. But the oldest tree on the list, an unnamed bristlecone pine from the same location, has a core suggesting it is 5,067 years old.

This time-worn tree has lived through the rise and fall of the Roman Empire. It was already established when the Ancient Egyptians started building pyramids.bbc.com