If only bristlecone pines could talk, the stories they'd tell would include dozens of centuries of change. These trees can reach upward of 5,000 years of age despite the fact that they grow in unforgiving environments.
LiveScience writes, "The Great Basin Bristlecone Pine (Pinus longaeva) is considered to be one of the oldest living organisms found anywhere on Earth. Along with its genetic cousins, the Sierra Foxtail Pine (Pinus balfouriana) and the Rocky Mountain Bristlecone Pine (Pinus aristata), these ancient sentinels stand at the highest elevations of the Rocky Mountains, just below the tree line. They are scattered across high, mountain regions of the states of California, Nevada, Arizona, Utah, Colorado and New Mexico."
At these high elevations, cold temperatures and high winds are common. The growing season is short and in some years the trees don't even show a new ring of growth. They grow an average of just 1/100th of an inch wider every year. They don't even grow seed cones every year. It takes a full two years for cones to mature so seeds can spread.
The harsh environment has some benefits that the trees have utilized for their advantage. The soils bristlecones can thrive in restrict the growth of other plants so there is little competition for precious nutrients and water. Without much surrounding growth, there is little danger of wildfires. And the wood of the slow-growing trees is very dense, which helps them ward off disease and insects.
These trees are made to be survivors and they often survive to incredibly old age. The oldest bristlecone is 5,065 years old, and perhaps one of the most famous of the trees is Methuselah, which is about 4,846 years old. Another bristlecone, called Prometheus, that was possibly more than 5,000 years old was infamously cut down in the 1960s by a researcher. It can easily be assumed that there are other older trees out there, whose ages have simply not been measured yet.