As an expert in the field of natural sciences and environmental studies, my focus lies in understanding the longevity of various organisms and their significance to the ecosystems they inhabit. When we consider the question of the longest living thing on Earth, it's crucial to differentiate between various forms of life, such as plants, animals, and even microorganisms, as each has its own unique longevity characteristics.

Plants, particularly certain species of trees, have been known to live for thousands of years. Among them, the **Great Basin bristlecone pine (Pinus longaeva)** stands out as an exceptional example. This species is native to the western United States, particularly in the Great Basin region, which includes parts of Nevada, California, and Utah. The longevity of these trees is attributed to a combination of factors including their adaptation to harsh alpine conditions, slow growth rates, and resistance to disease and pests.

The age of a bristlecone pine is determined by counting its annual growth rings, which are visible in cross-sections of the tree trunk. Each ring represents one year of growth, and by counting these rings, scientists can accurately determine the age of the tree. The oldest known bristlecone pine, named Methuselah, was measured to be 4,850 years old as of the last measurement in 2012. However, there is another tree in the same region, known as Prometheus, which was once considered the oldest until it was accidentally destroyed in 1964. The exact age of Prometheus at the time of its destruction is a subject of debate, with some estimates suggesting it could have been over 5,000 years old.

It's important to note that while Methuselah is the oldest known individual tree, there are other contenders for the title of the longest living thing on Earth. For instance, clonal organisms such as the quaking aspen (Populus tremuloides) in the United States and the Old Tjikko, a Norway spruce tree in Sweden, have been dated to be thousands of years old. However, these are not individual trees but rather genetically identical colonies that have been continuously regenerating from a single original organism.

Animals, on the other hand, have a much shorter lifespan compared to some plants. The longest living animals include species like the giant tortoise, which can live over 100 years, and certain types of whales that have been known to live for several decades. However, none of these animals come close to the longevity of the oldest known trees.

Microorganisms can also exhibit remarkable longevity, particularly in the form of endoliths, which are organisms that live inside rocks. These organisms can survive for thousands of years due to their ability to withstand extreme conditions.

In conclusion, when considering the longest living thing on Earth, the Great Basin bristlecone pine takes the title for the oldest known living individual nonclonal tree. Its longevity is a testament to its ability to adapt and survive in one of the most inhospitable environments on the planet. The study of these ancient organisms not only provides us with a glimpse into the past but also offers valuable insights into the resilience and adaptability of life on Earth.

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A Great Basin bristlecone pine (Pinus longaeva) is measured by ring count to be 5067 years old. This is the oldest known tree in North America, and the oldest known living individual nonclonal tree in the world.read more >>