Even though we have not yet found proof of life beyond our planet, in recent years scientists have detected more and more places in the universe that could support life. It was only two decades ago that astronomers discovered the first planet orbiting a star other than the sun, and now they estimate that the Milky Way alone may be home to over seventeen billion Earth-sized worlds. What might life look like on those faraway planets, where conditions are drastically different from our own? Driven in part by the desire to answer this question, a range of scientists have sought out life-forms that thrive in some of the most extreme places on Earth: miles below the ocean surface, in the frigid deserts of Antarctica, and far underground in sweltering gold mines, to name just a few. This has led to an unexpected consequence: As humanity begins to grapple with the likelihood of extraterrestrial life, we're also reaching a fuller understanding of just how alien organisms can be right here on Earth.
It is against this backdrop that journalist Caspar Henderson offers The Book of Barely Imagined Beings. Loosely inspired by Jorge Luis Borges's Book of Imaginary Beings, which catalogues the mythical and make-believe beasts that inhabit world literature, Barely Imagined Beings offers an illustrated, alphabetical compendium of some of the weirdest, wildest forms of life on Earth. Grounded in scientific knowledge but making no claims to be as inclusive or objective as an encyclopedia, Henderson's book bills itself as "a twenty-first-century bestiary," hearkening back to the ancient and medieval creature catalogues that were more concerned with evoking wonder than checking facts.
Facts, however, do matter to Henderson, who approaches his material with a deep respect for evolutionary science and a sophisticated understanding of the many other ways humans have tried to make sense of the natural world and our place in it. The medieval bestiary was one of those ways, weaving together "zany pictures, bizarre zoology and religious parables" in an attempt to "understand and convey how things actually are"—or at least how Europeans at the time perceived them to be. The pelican, for example, becomes a Christ-like figure of self-sacrifice, piercing her own breast to draw blood to feed her young, while the salamander and its supposed ability to survive in fire are presented by Saint Augustine as proof "that everything which burns is not consumed, as the souls in hell are not." In bestiaries, Henderson writes, "even creatures we know to be real become fantastical."
In Barely Imagined Beings, the equation is reversed: The beasts described within, Henderson argues, are all the more fantastic for being real. "Many real animals are stranger than imaginary ones," he writes, "and it is our knowledge and understanding that are too cramped and fragmentary to accommodate them." Unlike Borges, who set out to catalogue every monster and mythical beast that humans had imagined, Henderson wants to document those creatures of which we cannot even begin to dream.
Most of the book's strangest organisms are aquatic, reminding us that the oceans may be home to the closest things we have to alien life on Earth. There's the gonodactylus (better known as the mantis shrimp) and its extraordinary eyes, which have twelve color receptors—as opposed to the human eye's three—and can detect the polarization of light. In the chapter titled "Eel . . . and Other Monsters," a diagram details the moray's "extraordinary ability to vomit up a second set of fearsome teeth." And then there's the yeti crab, undiscovered until 2005, which cultivates gardens of bacteria on its bristly claws and lives in the waters around hydrothermal vents, where temperatures plunge from seven hundred and fifty degrees to just above freezing in the space of a few feet. Other creatures in Barely Imagined Beings are more familiar, like the dolphin, the flatworm, and the octopus, but in Henderson's hands, they all manage to surprise.
Each of the twenty-six chosen animals gets its own self-contained essay, but many of these essays do little to illuminate their subjects. In the nautilus chapter, for example, Henderson considers the beauty of the animal's easily fossilized shell and tries to imagine the cognitive dissonance experienced by the scientists who first realized that the Earth has been around for much longer than humans have. He then takes us on a brief detour into the history of submarines, compares the nautilus's pinhole eyes to the earliest camera obscuras, and ends with a mediation on time as an endless progression of fleeting snapshots. If you were hoping for an exhaustive description of the nautilus, you've come to the wrong place. But if you let the book's innumerable digressions wash over you, you'll realize that animals are not Henderson's principal subjects. Barely Imagined Beings, is, in the end, a book about what it means to be human.
Henderson is not the first writer to use our perception of animals to try to reveal something essential about humanity, but this primordial relationship has never had higher stakes. Most scientists now believe the Earth has entered a new geological epoch called the Anthropocene, in which human activity is the most influential force on the planet. We, just one of Earth's millions of species, have the ability to remake the world in our image, no matter what the cost is to other life forms. Already, several of the species Henderson documents in this book, including the right whale, the leatherback turtle, and the long-whiskered owlet, continue to exist only because we have decided they are worth protecting.
If Barely Imagined Beings contains any moral lessons, like the bestiaries before it so often did, it is that humans' "cramped and fragmentary" understanding of life on this planet should not doom the very real creatures that we rarely see, and could hardly imagine. As far as we know, humans are still among the few beings in the universe able to even conceive of experiences outside of our own. Barely Imagined Beings suggests that we should take advantage of this extraordinary if not entirely unique ability. We should revel in our imagination and learn to appreciate that just because some of our fellow earthlings seem alien to us, it doesn't mean that they're not right at home.
Lizzie Wade is a contributing correspondent for Science magazine.