A weird, related thought: Millions of years ago trees lived and died. But their fallen bodies never decomposed because no life form existed who could make a living out of breaking down wood. In the nick of time (I made that part up) a hero arose who could feed on the cellulose and lignin, converting those into their softer tissues, which in turn begin to decompose when the fungal fruiting bodies die. Hail to thee, Fungi; you saved us from the deadly pile of wood!