Beavers have been around a long time – building dams, swimming in their ponds – generally living the beaver dream. Exactly how long ago do we have proof of them building dams and chewed down trees?
The oldest intact fossilized beaver dam was found in Canada and is dated as approximately 125,000 years old. That must have been one sturdy dam to stay intact for so long! What’s really cool is similar to how modern beavers pack river rocks the size of soccer balls into their dams for added weight and stability, the foot bones of a woolly mammoth were found packed into the fossil dam.
Near that fossilized dam, fossilized sticks with characteristic beaver teeth chew marks on them were also found – some of which dated 4-5 million years old! So beavers have been chewing wood, and probably building dams for at least 5 million years, and some of their dams are so solidly constructed that they stay intact for over a hundred thousand years!