A commercial fisherman measures a spiny lobster. (Whitney Shefte/The Washington Post)
Bailey Steinworth is a third-year Ph.D. student studying evolutionary developmental biology at the University of Florida Whitney Laboratory for Marine Bioscience.

The controversial Canadian psychologist Jordan Peterson wants you to know that you’re a lot like a lobster. In the first chapter of his best-selling book, “12 Rules for Life: An Antidote to Chaos,” he singles out this crustacean to demonstrate how we can exploit the fundamental principles of nature to achieve material, social and spiritual success.

According to Peterson, there is an “unspeakably primordial calculator, deep within you, at the very foundation of your brain, far below your thoughts and feelings,” that “monitors exactly where you are positioned in society.” ­In other words, no matter how sophisticated we humans believe ourselves to be, deep down, we’re supposedly motivated by the same drive for dominance as lobsters. Want to “embark on the voyage of your life, let your light shine, so to speak, on the heavenly hill, and pursue your rightful destiny”? Assume the upright posture of the biggest, baddest lobster on the reef, or as Peterson says, “Look for your inspiration to the victorious lobster, with its 350 million years of practical wisdom. Stand up straight, with your shoulders back.”

I’m a marine biologist, and despite my deeply held affection for all marine invertebrates, I confess I was a little puzzled by Peterson’s fixation on lobsters. It’s not that he gets the science wrong, exactly, just that his choice is a little too convenient. The facts he identifies do arguably square with his own “stand up straight with your shoulders back” advice. But in asking us to consider the lobster, he’s cherry-picking one model of social behavior when there’s a whole ocean full of equally relevant examples.

To understand the similarities between any two organisms, biologists look back through evolutionary time to their most recent common ancestor. In the case of humans and lobsters, our most recent common ancestor was defined by the remarkable evolutionary innovation of a complete gut — meaning that the mouth and anus are two separate openings (the importance of this morphological novelty is clear when you contemplate the alternative). The living animal that probably most closely resembles this ancestor is the acoel, a mostly harmless marine worm no bigger than a grain of rice. Acoels’ social interactions are limited to mating — they’re typically hermaphroditic, so each individual acts as both “male” and “female” — or sometimes to cannibalism, if a hungry acoel encounters another small enough to fit in its mouth. I suppose cannibalism is a sort of dominance hierarchy, but acoels don’t engage in the complex displays of aggression seen in lobsters or form social hierarchies like primates. If the common ancestor of humans and lobsters lacked dominance hierarchies (which seems likely, based on what we know about living animals), then our two species’ social behavior evolved independently, and the one can’t inform us about the other.

As a psychologist, Peterson understandably seems to favor lobsters because of their well-characterized behavioral repertoire, citing among other things research on the neurotransmitter and antidepressant target serotonin. But they’re not the only inhabitant of the ocean that’s been studied in this way. He might also be interested in Aplysia. Like lobsters, sea hares of the genus Aplysia — sea slugs named for sensory structures that resemble rabbit ears — have been used extensively in serotonin studies. Behaviorally, however, lobsters and sea slugs could hardly be more different: While a lobster rarely wants to see another lobster, a sea hare placed on its own will crawl toward chemical cues indicating the presence of other sea hares. In fact, being with other members of its species improves a sea hare’s ability to learn and remember. Peterson’s opening chapter emphasizes that male lobsters compete for the best territory to win access to the most females. By contrast, in sea hare sex, everyone gets a turn. They’re hermaphrodites that mate in groups, alternating between the “male” and “female” roles.

Sea hares’ “big pile of hermaphrodites” mating strategy is shared by many species, including the aptly named sea snail Crepidula fornicata. Since they’re small, males fasten themselves atop a stack of other snails, with large females at the bottom. As an individual grows, other small males will join the stack above him, until finally he’s big enough to change into a female. Sequential hermaphroditism — starting life as one sex, then changing to another — makes sense as a strategy considering that the cost per gamete is higher for eggs than sperm. In other words, for reproduction, size matters more for females than males. Hermaphroditism is so common that it’s possible the ancestor of all animals was a hermaphrodite, and some of our most distant relatives in the animal kingdom, the ctenophores, are almost all hermaphrodites. (I don’t know how they divide up the task of representing “chaos” and “order,” to cite two of Peterson’s favored terms.)

These examples of social behavior are more reproduction-focused than is Peterson’s discussion of lobsters, but that’s because for a lot of animals, social interaction can be divided into “mating” or “existing near each other without a problem.” As Peterson points out, lobsters’ aggressive displays arise from their need to fight for access to quality shelters and territory where they can scavenge for food. Species with better predator defenses and more plentiful food sources don’t need to fight: Algae-grazing Aplysia defend themselves by releasing ink clouds and tasting terrible, and hard-shelled C. fornicata eat by filtering particles out of the water. There are animals more ancient than lobsters that derive benefits from being near each other: For my study animal, Cassiopea, also known as the upside-down jellyfish, mutual proximity is a defense strategy. In the shallow, warm waters of the Florida Keys, huge groups of Cassiopea pulsate gently on the ocean floor while the algae that live in their cells soak up sun to make their food. When disturbed, this Jimmy Buffett of jellyfish deploys masses of microscopic stingers in clouds of mucus. More jellies mean a larger volume of weaponized snot and a nastier surprise for a potential predator (or researcher, as I’ve learned the hard way).

Even in generally solitary species, sex is often a group event, and it’s been that way for millions of years. During the highest tides of summer, certain beaches on the east coast of North America are flooded with mating horseshoe crabs. As with lobsters, fossil evidence of horseshoe crabs predates the dinosaurs, and as with lobsters, the horseshoe crab’s front legs have evolved into specialized pincers. But these are tools of love, not war: In males, the first set of appendages are specialized for latching onto the carapace of a female during mating season, sometimes for weeks at a time. Females crawl out of the ocean to lay eggs on the beach, each dragging a lucky male behind her. As she lays her eggs, the male fertilizes them externally.

Each mating pair may be surrounded by as many as 12 additional males, a scene that seems to neatly fit Peterson’s understanding of nature as ultracompetitive: The strongest win and the weakest fail, fathering no offspring. But that’s not what’s happening at all. Older “satellite” males in poor condition adopt a different strategy that doesn’t involve unseating a strapping young competitor. Instead, they sidle up next to the female and deposit sperm into the nest from a different angle. A single satellite male can father more than half the offspring in a clutch, and if two or more satellite males are present, the “primary” male may not father many at all. Don’t feel too bad for him, though — they’ll all be at it again for the next few nights, potentially with very different paternity outcomes.

Our animal relatives have evolved specifically to survive in their unique environments, just as much as we have evolved to fit ours. No biologist would argue with Peterson that dominance hierarchies have probably existed for a long time, but it’s also true that plenty of animals live together without the need to assert dominance over one another. It seems as if his discussion of lobsters illustrates far more about his own worldview than it does about human behavior, but he’s the psychologist, not me. Peterson tells his readers to draw inspiration from an animal that can’t stand interacting with its own species outside of sex. I say life is so bizarre and beautiful that there’s inspiration to be found everywhere.