The cluster of more than 40,000 trees in rural Utah is the largest single organism in the world, all from a single seedling. But that’s not all: According to a team of researchers, the forest—known as Pando—may be the oldest living thing on earth.
Although it consists of more than 40,000 trees, Pando is a single organism that came from a single seed. However, the very moment that seed sprouts, it stays high in the air. According to the team that recently estimated the age of this creature, Pando is between 16,000 and 80,000 years old. In other words, sometime between the glaciers retreating from Manhattan and the last time the Tsuchinshan-ATLAS comet passed across Earth’s sky, a seedling in what would become Utah began to form Pando. The team’s research at Pando has not been peer-reviewed and is hosted on the bioRxiv preprint server.
The forest that makes up Pando is the largest, densest animal yet known, weighing in at about 13 million kilograms (5.9 million pounds) and covering 106 hectares (43 acres), according to the US Forest Service. Based on recent research, Pando may have been 40,000 years old when the Neanderthals disappeared from the fossil record about 40,000 years ago.
“We studied a very unique animal, whose size made us wonder about evolution over time and space,” said Rozenn Pineau, a researcher at the University of Chicago and lead author of the study, in an email to Gizmodo. “We expected that trees that are close in space are more genetically related. We find that it is, but to a much lesser extent than we expected.”
To estimate the age of the clone, the research team genetically sequenced more than 500 samples from Pando and its neighbors. The team sampled a variety of tree tissues including leaves, roots, and bark, and programmed somatic transformation of the clone from viral transformation. Lineage mutations occur in the reproductive cells of the parent and are inherited, while somatic mutations are changes in DNA that occur after the cell is fertilized. These mutations occur over the course of an organism’s life, and the rate of these mutations allowed the team to estimate the approximate age of the grove.
“Organisms that reproduce cooperatively can also achieve very long life spans, making somatic mutation an important mechanism for creating dynamic variation in Darwinian evolution through natural selection,” the research team wrote in the paper. “However, little is known about the rate of evolution of living organisms and the evolutionary mechanisms of long-lived species.”
The researchers created phylogenetic models that explained how mutations were introduced into the Pando clone over time, giving them a range of ages for the ancient grove. The team estimated Pando’s age to be somewhere between 16,000 and 80,000 years old—an admittedly wide range, though evidenced by the presence of aspen pollen in soil samples taken from nearby Fish Lake.
“Despite the spread of roots being restricted by area, we observed a positive correlation between genetic distance and area, which suggests the existence of a mechanism that prevents the accumulation and spread of genetic mutations in all units,” the team wrote in the paper. In other words, although Pando’s roots are limited in terms of spread, its genetic makeup is remarkably similar. Some unknown mechanism appears to limit changes in accumulation across the region, the researchers suggest.
“To look at the uncertainty in the call step, we tested three scenarios, which is why our age range is so wide,” Pineau added. “It is more likely that you came to a small window. Indeed, colleagues at UC Berkeley are currently working to obtain high-resolution genetic data to help narrow this window. “
According to the Forest Service, Pando is declining due to browsing by animals including deer, and attacks by beetles and bark beetles. Foresters are working to encourage Pando to grow new trees, lest this ancient living miracle go the way of the dodo. Or a hairy rhinoceros. Or a mammoth. Any other species that were around Pando, but couldn’t survive it.
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