Lichen: 400,000,000 years of two-species partnership and counting. Fir needles: 280,000,000 years and counting.

That’s a gap of 120,000,000 years, when lichens got their acids from rocks, rather than from trees, which got them from rocks. But after those lonely days, it’s often been a three-way partnership. Or four. Wolves and coyotes no doubt mark logs like this. And from time to time a bear comes along and gives the whole thing a whack.