Among animals, few species live longer than the human being. Partly thanks to our biology, and partly thanks to the development of medicine, Homo sapiens is in that small privileged group of species that exceeds 60 years of life .
But that time is nothing for many plants. Whether it’s because they grow extraordinarily slow, or because they keep forming new stems from a network of roots, plants are able to cheat time and stay alive for centuries, even millennia . On Elephant Island, in Antarctica, there is a moss that is estimated to be 5,500 years old . Also in boreal environments, but in the northern hemisphere, we find Old Tjikko in Sweden, a spruce that, with a single trunk, is the oldest unitary and non-colonial specimen, with more than 9,500 years of age .
But even these organisms fall short when we compare them with the longest living beings on the planet.
The Mojave yucca and other ancient plants
We speak of clonal colonies when a population of what appear to be many individuals descend from the same ancestor, from which they originate by vegetative reproduction , not sexual reproduction. When all these apparent individuals, such as the trunks of a forest, remain connected to each other by roots, then we can say that the entire colony forms a single individual . These types of individuals that appear to be populations are called ramets .
This effect is what we find in the Mojave yucca , a shrub that has been growing radially, the stems of the central area have been dying, but the roots remain and continue to grow outwards, where new stems continue to emerge, forming a ring aspect. It is estimated that this individual in ramet can exceed 11 700 years old .
Other examples of truly ancient clonal populations are Palmer ‘s oak , in Riverside, California, or a population of eucalypts found in New South Wales, Australia. Both are clonal populations that share roots, whose age is estimated at 13 000 years .
King’s holly is a very strange plant. With the scientific name Lomatia tasmanica , it is a triploid plant, that is, its chromosomes are distributed in triplets, and not in pairs. This causes sterility in the plant, so it can only reproduce asexually. A large number of clones have been obtained from this tree for botanical gardens, all of them from the same wild population. It is estimated that its age exceeds 43,600 years .
Pando and Posidonia, bronze and silver in longevity
Among the largest plants in the world we also find the longest. One of these is Pando , a ramet specimen of aspen in central Utah. It started out as a single tree, but spread underground, new stems sprouting from the roots in a fully vegetative way. Over time, some stems died and were replaced by others, which sprouted from the same network of roots. In this way, this forest, formed by a single individual, renews its aerial parts while the roots continue to expand . The average age of each trunk is around 160 years, but the network of roots, which extends over 43 hectares, is estimated to be around 80 000 years old.
Even older, according to estimates, is the clonal colony of Posidonia oceanica that we find in an extension of up to 15 kilometers between the islands of Ibiza and Formentera. It is an underwater plant – not an algae – that continues to grow and expand through underground rhizomes. This specimen, which itself forms an entire underwater meadow —the climax community of the Mediterranean Sea— is considered the longest living being in the world, with an estimated age of between 80,000 and 200,000 years . It seems like a very difficult record to beat. And no plant has outgrown it that we know of.
siberian bacteria
And yet, the record is surpassed by other types of organisms .
Let’s leave the plants to enter the mysterious world of bacteria. In the Siberian ice we know that there are microorganisms that have been frozen for long periods of time, waiting to emerge. Bacteria that remain in a state of latency, with their metabolism stopped, and that return to perform their biological functions when the environment is favorable again.
However, even in latency, the effects of genetic decay are inescapable. DNA cannot remain immutable in time , not even frozen; it degrades little by little, making the organism increasingly unviable. A bacterium frozen for millennia could therefore not be viable again, as its DNA would be too degraded.
But that was not what a research group that analyzed dormant bacteria in the ice of Siberia found. They found living organisms that were up to half a million years old, and with their DNA intact . And it is that those bacteria had not been in a state of latency all that time, their metabolism had continued to function and repair the DNA as it was degrading.
These actinobacteria, of the genus Arthrobacter , are, at half a million years old, the longest living beings that we know of.
References:
Arnaud-Haond, S. et al. 2012. Implications of Extreme Life Span in Clonal Organisms: Millenary Clones in Meadows of the Threatened Seagrass Posidonia oceanica. PLOS ONE, 7(2), e30454. DOI: 10.1371/journal.pone.0030454
DeWoody, J. et al. 2008. “Pando” Lives: Molecular Genetic Evidence of a Giant Aspen Clone in Central Utah. Western North American Naturalist, 68(4), 493-497. DOI: 10.3398/1527-0904-68.4.493
Johnson, S. S. et al. 2007. Ancient bacteria show evidence of DNA repair.
Proceedings of the National Academy of Sciences, 104(36), 14401-14405. DOI: 10.1073/pnas.0706787104
Sussman, R. et al. 2014. The oldest living things in the world. University of Chicago Press.
