What Are the Oldest Living Things? Trees, Clones and a Definition Problem

The uncontested record for a non-clonal individual, meaning a single organism that grew from one seed and has one connected body, belongs to the Great Basin bristlecone pines of the White Mountains of California and Nevada. A specimen named Methuselah was dated by counting growth rings in a core sample at around 4,850 years old, and an older one of roughly 5,070 years has been reported from the same area; their locations are not published, for reasons that will become clear. They survive because their conditions are terrible: they grow at three thousand metres on dolomite soil that almost nothing else tolerates, extremely slowly, with dense resinous wood that resists insects and rot, and with much of the trunk dead while a narrow strip of living tissue carries water to a few branches. Other very old single trees include an alerce in Chile estimated at over three thousand years and several yews in Britain whose ages are debated because they hollow out, which destroys the inner rings and removes the evidence.

Many plants spread by sending out roots or runners and producing new stems that are genetically identical and physically connected, which makes the whole stand arguably one organism:

• •Pando, a quaking aspen colony in Utah covering forty-three hectares with around forty-seven thousand stems from one root system, estimated at several thousand years and possibly far older, and currently failing to regenerate because deer eat the new shoots
• •A Posidonia seagrass meadow between Spain and Formentera, estimated by genetic analysis at between eighty thousand and two hundred thousand years, which would make it the oldest living thing known
• •King's holly in Tasmania, a shrub that produces no viable seed and reproduces only by cloning, with fossil leaf fragments of the same genotype dated to around 43,000 years
• •A creosote bush ring in the Mojave Desert, growing outward from a centre that died long ago, estimated at around twelve thousand years
• •Individual stems in each case live an ordinary lifespan and die while the organism continues, which is what makes the dating both possible and contestable

Three separate questions get tangled. The first is what counts as one individual: if the connecting roots of an aspen stand rot away, leaving genetically identical but separate stems, is it still one organism or many, and the answer is a convention rather than a fact. The second is whether the organism is old or merely its genome is, since no cell in Pando is thousands of years old and what persists is a lineage of continuously replaced cells, which is also true of a human body over decades and is usually not thought to make a person younger. The third is what counts as alive: a bacterium revived from a salt crystal or from permafrost has been dormant rather than active, and claims of bacteria revived after 250 million years or of a 46,000-year-old nematode worm brought back from Siberian permafrost in 2023 raise the question of whether suspended metabolism is life continuing or life restarted. Scientists generally handle this by stating the criterion being used rather than by arguing for one, which is why published records differ.

The methods vary in reliability. Dendrochronology, counting annual growth rings, is precise where rings are annual and complete, and it requires either a core sample taken with a borer or a cut stump; it fails where a tree produces no ring in a bad year, produces two in an odd one, or has a hollow centre. Radiocarbon dating works on dead material and gives an age for the carbon rather than for the organism, which is useful for clonal colonies where old fragments survive. Genetic methods estimate clonal age from the number of accumulated somatic mutations against an assumed rate, which is how the seagrass figures were obtained and which carries wide uncertainty. Growth rate extrapolation, dividing size by an assumed annual increment, is the least reliable and is responsible for several inflated figures that circulate widely. The variation in method is why any list of oldest organisms depends heavily on which evidence the compiler accepts.

The most famous cautionary story in the field concerns a bristlecone in Nevada. In 1964 a graduate student studying ice age climate obtained permission to cut down a tree after his corer broke in it, and the stump turned out to have around 4,900 rings, making it older than anything then known. The tree, called Prometheus, was dead and the specimen is still studied, and the episode changed practice permanently. Locations of the oldest specimens are now withheld, published coordinates are omitted, and the trees are not signposted, because the documented risks are vandalism, souvenir-taking and simple soil compaction from visitors standing on shallow roots. The same logic applies to several other record holders. The deeper point the field keeps making is that extreme longevity is associated with harsh, marginal, unprofitable ground, since a tree that grows fast in good soil is harvested, outcompeted or blown over, and the oldest living things on Earth have survived by growing where nothing else wanted to be.

The oldest verified single organism is a Great Basin bristlecone pine of about five thousand years, growing extremely slowly on poor high-altitude soil with most of its trunk dead. Clonal colonies are older and harder to define, including a Utah aspen stand of forty-seven thousand connected stems and a Mediterranean seagrass meadow estimated at up to two hundred thousand years. The records depend on whether one counts a connected clone as an individual and whether dormancy counts as living, and the oldest specimens' locations are kept secret after one was cut down in 1964.