People do not realize just how important Fungi are - there was a point at which Trees were the new hotness and Fungi had not evolved yet - prehistoric trees basically took over the entire planet and there was nothing to break down all of the leftover dead wood on the ground. We are talking layers and layers of dead trees everywhere.
Then Fungi evolved and started breaking all that down and eventually a long time later we get animals.
Fungi were on land before trees (they broke down rocks to make soil, and were the OG roots). It took them a while to learn to digest.. I think lignin was it?
Half remembered from first chapter of Entangled Life.
IIRC the layers of dead trees also caused pervasive fires. One because of the fuel from the trees, but also because oxygen levels were much higher due to large amount of carbon trapped in the trees.
Apparently much of worlds coal was also from this period.
I wonder how those trees communicated then. I am reading "the hidden life of trees" at the moment, which talks quite a bit about how trees communicate using fungi. The fungi benefit from this by receiving certain nutrients.
Its an interesting symbiotic relationship for sure. When I was backpacking in Alaska I was basically walking non stop on lichen (which sort of looks like large tuft balls of colorful and very tiny coral reefs but super soft and springy). All of the animals there eat tons of this stuff. Its basically a hybrid between a plant and a fungi (not just a symbiotic relationship). Sort of like fungi-moss.
Then Fungi evolved and started breaking all that down and eventually a long time later we get animals.