You had us all fooled, Tree 76. Up til now, scientists believed that the tallest redwood in California's Muir Woods was about 1,500 years old, the Los Angeles Times notes. But the 249-foot-tall giant—or, as the San Francisco Chronicle now refers to it, "a puerile sprig in the hallowed halls of old growth"—likely came to be about 777 years ago. Allyson Carroll, a dendrochronologist (aka tree-ring expert) at Humboldt State University, discovered the discrepancy when she compared Tree 76's rings to those of its relatives around other parts of California.
Carroll also pinpointed the ages of two fallen redwoods in the forest at 693 years old and a youthful 536, lending credence to the theory that Muir Woods is relatively young compared to the redwoods and sequoias further north: A coastal redwood cited by both the Times and the Chronicle is a mature 2,520 years old. So why is the famous forest so much younger than its cousins? Carroll notes that natural events like landslides or fires may have wiped out older trees somewhere down the timeline, per the Chronicle. (Climate change may be making the redwoods grow faster.)