The Earth’s Oldest Organism. Scientists have discovered that the largest organism on Earth is also the most ancient.

The age of the Earth exceeds 4.5 billion years, and during this time, our planet has become home to an incredible number of living organisms. While the age of these organisms may only be a number, for the largest organism on Earth, known as Pando, this figure could be so vast that it would leave all other beings far behind, according to Science Alert.

In a new study, a group of scientists from the United States sequenced hundreds of samples collected from an extensive network of trembling aspen (Populus tremuloides). The results suggest that the 43-hectare forest could have started as a solitary seedling long before the end of the last Ice Age—around 34,000 years ago. Interestingly, less conservative estimates confirm that the first Pando tree may have actually sprouted tens of thousands of years earlier.

It is worth noting that the new work by the scientists has not yet undergone peer review, but its findings help narrow down assumptions about how long this cloned and largest organism on Earth has existed. Interestingly, current estimates suggest a wide variability: from several thousand years to over a million years.

The researchers highlight that Pando is considered the largest organism on Earth, consisting of 47,000 individual trees. The uniqueness of this forest lies in the fact that all these trees share the same genetic heritage and a single interconnected root system—essentially making the trees "clippings" from the same old block.

The authors of the study note that the oldest known individual is an unnamed Bristlecone pine in the White Mountains of California, which is believed to be just over 5,000 years old. Unfortunately, cloned organisms like Pando follow different rules. Essentially, their genome does not easily mix with others within the species, limiting the plant's reproduction to asexual clones—all of which remain connected, carving their way through the surrounding environment.

Interestingly, Pando has previously been suspected of extraordinary ancient age. In the new study, scientists aimed to shed light on this mystery. To do this, they collected about 500 fragments of roots, leaves, and bark, as well as samples from other, non-related aspens. The researchers then sequenced their DNA.

The team employed analytical methods to identify changes that occurred over time. As a result, they discovered about 4,000 genetic variations in the various samples. The patterns of their mutations told an intriguing story, with one of the models dating back somewhere between 16,000 and 80,000 years.

According to co-author of the study, geneticist from the University of Chicago, Roseanne Pino Helene Kudiabor, one would expect that spatially close trees would be genetically closer; however, the scientists did not find this. Instead, they noted that the spatial signal was much weaker than expected.

In future studies, researchers aim to find out why Pando's mutation history has spread in such a way as to avoid the accumulation of less beneficial genes. Consequently, the scientists hope to understand why this organism and others like it are capable of living to such an age. It is important to note that the results of the scientists' work are particularly significant, given that in recent years, researchers have sounded the alarm—Earth's largest organism may be at risk of disappearing.