Most people know that you can count a tree’s rings to determine its age. But what makes a ring count for a year?
Remember that a tree’s true “wood” is really only the central tissue that conducts water up from the roots. Around this constitutes the bark, which includes living tissue that distributes various substances (e.g., photosynthetic products) as well as the dead cork.
Focusing on this inner wood, development of these cells varies across a given growing season. In the spring and early summer, there is much water and minerals (thanks to melted snow), but as summer progresses, they are depleted. By autumn, the wood cells are smaller than what were produced earlier. (Winter, due to its cold, does not allow many cells to be produced.) The cycle restarts the following spring. The study of these processes, by the way, is called “dendrochronology.”
The earlier cells (known as early wood or springwood) are the larger cells, followed by those smaller cells formed later in the season (late wood or summerwood). The darker late wood abuts the following season’s early wood, thus separating the years marked.
To conclude, some of the oldest trees are 4,000 years old. Some dead trees, dated to be 5,000 years old, using radioactive carbon dating. When the earliest trees were germinating, human history (in the strictest sense) was just dawning. Since this falls within the domain of the 6,000-10,000 years of young earth creationism, yet discussed by an anonymous evolutionist and liberal Christian, sorry, that’s a contradiction in terms.