Not so sure about that. According to history, the original tree was burnt down by a wife of King Asoka. However a sapling from the original tree had been planted in Sri Lanka and the tree in Bodh Gaya has grown from a sapling of that tree. Trees do live for these long periods. I've heard that the oldest tree related to the Buddha is in Sravasti planted from a sapling of the original Bodhi tree by Sariputra.
