Mycorrhizal fungi colonised plant roots roughly 450 million years ago and biologists now suspect plants could never have moved out of the oceans onto bare rock without them, meaning every forest on Earth — including the redwoods, the Amazon, and the boreal belt — is still running on a partnership older than trees themselves

The first land plants did not have roots. They had stubby green tissue pressed against bare Ordovician rock about 450 million years ago, and the only reason they survived long enough to become ferns, then conifers, then oaks, was that a thread of fungus reached up out of the mineral grit and traded them phosphorus