Over the run of eighty minutes, I tried to convey to a coven of twenty-one-year-olds with a wide spectrum of intellectual abilities just how absurd it was for everything to spring up out of nothing. The alignment of favorable circumstances for the emergence of self-assembling molecules seemed astronomically unlikely. But the appearance of protocells almost as soon as the molten Hadean Earth cooled suggested that life was the inevitable by-product of ordinary chemistry.

“So the universe is either pregnant everywhere, or barren. If I could tell you which, beyond all doubt, would it change your study habits?”

That got a polite, Okay-Xer chuckle out of the happy few who were paying attention. But the rest had signed off. I was starting to lose them. It takes a certain kind of strangeness to hear the cosmic symphony and to realise that it was both playing and listening to itself.

“Here on Earth, it was archaea and bacteria and nothing but archaea and bacteria for two billion years. Then came something as mysterious as the origin of life itself. One day two billion years ago, instead of one microbe eating the other, one took the other inside its membrane and they went into business together.”

I looked down at my notes and came unstuck in time. My wife-to-be twenty minutes after having me for the first time, was lying with her nose against my floating rib. I love your smell, she said.

I told her, “You don’t love me. You love my microbiome.”

When she laughed, I thought: I’ll just stay here in these parts for a bit. Until I die, or so. I told her how a person had ten times more bacteria cells than human cells and how we needed a hundred times more bacteria than human DNA to keep the organism going.

Her eyes crinkled in love. So we’re the scaffolding, is that it? And they’re the building? Her scaffolding laughed again and climbed on top of mine.

“Without that bizarre collaboration, there’d be no complex cells, no multicellular creatures, nothing to get you out of bed in the morning. The friendly takeover took forever to happen. But here’s the weird thing: It took two billion years to happen. But it happened more than once.”