Wood that refused to rot for 60 million years

During the Carboniferous period, trees evolved a new structural material called lignin. It made them strong and tall, but it had one major flaw: bacteria and fungi hadn't evolved the enzymes to break it down yet. When a tree died, it just sat there, perfectly preserved, for centuries.

These dead forests piled up in massive heaps, dozens of feet thick. Because the wood wouldn't rot, the carbon inside it remained trapped instead of being released back into the atmosphere as CO2. This created an oxygen spike so massive that insects grew to the size of hawks and millipedes reached eight feet long.

This era of 'immortal' wood eventually ended when a specific type of fungus finally figured out how to digest lignin. If that fungus hadn't appeared, the Earth might have run out of atmospheric carbon entirely, freezing the planet as plant life suffocated.

All those unrotted trees were eventually buried under sediment and cooked by the Earth's internal heat. Today, we dig them up and burn them for fuel. Roughly 90% of the coal we use today comes from that single 60-million-year window when the planet forgot how to decompose wood.