If you’ve spent any real time with me (or even booked a 10-minute appointment in my clinic), you’ve probably noticed that I like to refer to humans as “talking apes” and occasionally mention that we’re all just “glorified worms.” The former helps me remember that we remain eternally beholden to our biological/sociological needs and often behave accordingly. The latter helps me remember that almost every animal descended from worms, and still essentially exists as just a digestive tract and set of genitals that traipses around looking for food and mates. I’m not sure why I keep that concept in my mind during everyday life, but it does make for interesting observation. It also helps me remember that time and thought as we know them originated in the lowly worm.
I should probably explain my reasoning, which expectedly starts on the primordial Earth.
Early lifeforms had it easy. Cells floated about in a near-frictionless world, in which chemical gradients (getting dunked in saltwater) posed more dire threats than physical stresses. Primitive life didn’t need to think much about gravity and could instead focus on perfecting metabolism, photosynthesis, and all the dazzlingly complex and vital biochemistry that keeps us 47 percent genetically similar to fruit flies. With no such thing as falling, grinding, or tearing, microscopic organisms and early animals just waggled their way through the world. Life was simple: it consisted of single celled organisms and sponges/seaweed clinging to rocks for survival (please bear with this oversimplification… I’m glossing over roughly three billion years of history).
But sometime between 600 and 580 million years ago, muscles appeared and helped newly-evolved netlike creatures (jellyfish) undulate their way to new pockets of delicious plankton. To undergo coordinated movements, they began sending electrochemical signals over long distances. Most jellies still function as (very effective) plankton traps. But with this new movement and size came new challenges from the physical world. Their larger bodices could suddenly be torn asunder by a swift ocean current or a run-in with a rock. In response, they evolved the first epidermis! Skin as we know it was born of necessity to keep the first large, mobile animals from falling apart once they had the ability to start flapping in the ocean.
Jellyfish Earth looked a lot like pre-jellyfish Earth (except there were jellyfish), and lasted until the precipice of the greatest biological diversification of all time—the Cambrian Explosion—541 million years ago. Until this time, animals had only two types of symmetry: radial (jellyfish: think spokes on a wheel) or none at all (sponges). Sponges don’t move with any real purpose, and jellyfish have only a top and bottom—they have difficulty swimming toward anything—and are therefore limited in the ways in which they interact with the world (with the exception of the box jellies, which evolved later and are actually capable of chasing fish). They didn’t have much need for directional motion, either; the only thing worth eating was plankton, and they’re no good for a chase.
But then worms appeared and changed everything. They were the first animals that exhibited bilateral symmetry—they had a front and back and a top and bottom—which meant they could point in a specific direction. Food went in the front (poo out the back), and a rudimentary neuromuscular system propelled them forward in search of booty and delicious num nums. The mouth end had basic sensory organs and a nerve ring (primitive brain) that helped the worms decide where to go. Finally, after three billion years of small-scale motion and sedentary life, a single organism could rapidly move long distances with purpose. Life awoke to the realities of the macroscopic world and found an entirely new way to inhabit the Earth.
The Cambrian Explosion was a true awakening. To make sense of this new, larger world, worms needed to collect information from disparate parts of the body, process it in a central location, then send cohesive responses in real time back to relevant parts of the body (say, by scurrying away from a threat). The old cellular machinery was simply incapable of the information processing and long distance messaging demands of large, mobile organisms. While cellular processes happen insanely fast, they operate on a very small scale, their parts (proteins) take a long time to build, and their messaging strategy relies mostly on painfully slow diffusion. These constraints made it impossible for large organisms like worms to rely on such machinery to make, and act on, split-second decisions. Animals needed to develop a way to instantly get all their cells on board with what the organism wanted to do.
To solve this problem, animal life piggybacked off the advances of the early neuromuscular system and set about using nerves to build an entirely new way to govern itself. Using ion channels that open automatically like dominos, nerve cells can send signals at a blistering 275mph, and can create complex neural networks that process information quickly. These mechanisms are plenty fast to help animals dodge an attacking predator. Starting with worms, animals began to make brains capable of bridging the gap between the lightning-fast but tiny world of cells, and the rough-and-tumble macroscopic world. The governance of living matter became a two-tiered system. DNA controlled cellular processes and body plan, but also coded for a superstructure (the brain) capable of directing the motion and intention of many cells at once at a time scale never possible before: at the speed of terminal velocity (plants can’t catch falling objects). Primitive electrochemical thought was born, and provided a way for life to experience spacetime at the rate humans do today. While bacteria may experience an hour as a lifetime and a growing vine may experience its days-long climb up a tree trunk as a quick jaunt, animals developed brains to experience time at the same rate we do today. Your understanding this sentence is a 540-million-year consequence of that evolutionary moment; every thought you’ve ever had has its deep origin in the mind of a primitive worm.
This development—conscious directional motion at the speed of falling—turned out to be one of the most useful things animals have ever learned to do, and every animal body plan (phylum) that exists today evolved in the ensuing 25 million years; an evolutionary eyeblink. Life had leveled up and found itself in an untouched world of endless possibility, with food everywhere and no rules other than to survive (cue Pure Imagination a la Willy Wonka). Animals took on incredible forms never seen before or since. Of the thousands of body plans that evolved during the Cambrian, only 35 survive today, but these phyla still account for every animal on the planet. Evolutionary diversification on this scale had never happened before and will likely never happen again (I hope not, anyway, since that would imply a horrific mass extinction). Animals were no longer simple aggregations of cells, but exquisitely organized life forms capable of moving through space with purpose. Most humans call this event the Cambrian Explosion; I call it The Great Wormification.
Now that they could sniff out and move toward food, worms could eat more than mud. They could eat each other! To aid in the ever-present predation cycle, worms developed arms, legs, eyes, claws, teeth, armor, and all manner of other appendages until they no longer looked like worms. These appendages helped them swim, climb, cling, and wriggle their way into new realms, from tide pools to the deepest oceans. Skin and eyes co-evolved as organs useful for hunting, camouflage, mating, and/or communication. New organs developed along the way to accommodate better oxygenation, circulation, waste elimination, and endocrine signaling. All the while, skin played a leading role in allowing animals to survive in ever more hostile environments. Eventually, animals living in the transience of the tides developed skin and oxygen exchange mechanisms (lungs) capable of transporting them from the sea into the harsh reality of dry land.
Over the ensuing eons, worms continued to look less and less like themselves, but the basics remain in place. Whenever you see a dog, fish, or butterfly, you’re really seeing a worm: a digestive tract with sensory organs/a mouth at the front, butt in the back, and genitals in between. Everything else is one of a variety of specialized appendages that evolution has provided to help it navigate the physical world.
By the time talking apes came along, worms had evolved such diverse appendages that most of us never really consider them (or ourselves) worms. Instead we call them things like insects, snails, and birds. We reserve the diminutive “worm” for those creepy crawlies most us would prefer not to consider, never quite having come to terms with the fact that despite all our thumbs and frontal lobes, we don’t just come from them; we are them.
Anyway, that’s what I try to remember when I look in the mirror. Also, that it’s odd for glorified worms to show affection for each other by touching mouth parts. Who decided that?