The earliest living things, way back in the Precambrian Era, were almost certainly either autotrophs (those that could produce their own nutrients from inorganic chemicals) or else scavengers. One of the reasons for this inference is that these early life forms had few in the way of hard, fossilizable parts, of the kind you might use to protect yourself from predators. Most of the fossils from that era are casts and impressions, and suggest soft-bodied organisms that, all things considered, had life fairly easy.
But the Cambrian Explosion saw the rather sudden evolution of exoskeletons, scales, spines... and big, nasty, pointy teeth. There's credible evidence that one of the main reasons behind that rapid diversification was the evolution of carnivory. Rather than waiting for your neighbor to die before you can have a snack, you hasten the process yourself -- and create strong selection for adaptations involving self-defense and speed.
After that, life became a much dicier business. I was discussing this just a couple of days ago with the amazing paleontologist and writer Riley Black (you should definitely check out her books at the link provided). She'd posted on Bluesky about the terrifying Cretaceous mosasaur Tylosaurus proriger, which got to be a mind-blowing twelve meters long (around the length of a school bus). This species lived in the Western Interior Seaway, which back then covered the entire middle of the North American continent. I commented to her what a difficult place that must have been even to survive in. "We always describe the Western Interior Seaway as 'a warm, shallow sea,'" Riley responded. "Ahh, soothing -- and not like 'holy shit these waters are full of TEETH!'"
What's interesting, though, is that even though we think of predators as mostly being macroscopic carnivores, this practice goes all the way down to the microscopic. The topic comes up because of a paper this week in Science about some research at ETH Zürich about a species of predatory marine bacteria called Aureispira. These little things are downright terrifying. They slither about on the ocean floor looking for prey -- other bacteria, especially those of the genus Vibrio -- and when they encounter one, they throw out structures that look like grappling hooks. The hooks get tangled in the victim's flagella, and at that point it's game over. The prey is pulled toward the predator, and when it's close enough, it shoots the prey with a microscopic bolt gun, and then chows down.
Aureispira isn't a one-off. The soil bacterium Myxococcus xanthus forms what have been called "wolf packs" -- biofilms of millions of bacteria that can be up to several centimeters wide, that glide along soil particles, digesting any other bacteria or fungi they happen to run across.
This one immediately put me in mind of one of the most terrifying episodes of The X Files; "Field Trip." In this freaky story, people are put into a series of powerful hallucinations after inhaling spores of a microorganism. The hallucinations keep the victim quiet -- while (s)he is then slowly digested.
Of course, the microbe in "Field Trip" isn't real (thank heaven), but there are plenty of little horrors in the world of the tiny that are just as scary. Take, for example, the aptly-named Vampirococcus, which is an anaerobic aquatic genus that latches onto other bacterial cells and sucks out their cytoplasm.
But the weirdest one of all is the bizarre Bdellovibrio, which is a free-swimming aquatic bacterium that launches itself at other single-celled organisms, moving at about a hundred times its own body length per second, then uses its flagella to spin at an unimaginable one hundred revolutions per second, turning itself into a living drill. The prey's cell membrane is punctured in short order, and the Bdellovibrio burrows inside to feast on the innards.
So. Yeah. When Alfred, Lord Tennyson said that nature is "red in tooth and claw," I doubt he was thinking of bacteria. But some of them are as scary as the mosasaurs I was discussing with Riley Black. The world is a dangerous place -- even on the scale of the very, very small.
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