Animals as varied as sharks, salamanders, and duck-billed platypuses can detect electric fields around them, while some fish, including the South American knifefish and various species of African elephantfish, can actually generate unique, complex electric fields, which they use to communicate information about their social status, sex, and dominance position within their social group.
Could animals like these exist in space? On a celestial body with completely dark oceans, such as Saturn's moon Enceladus, our notion of evolution would support this method of communication, leading us to believe that aliens on such a planet might concoct their language out of electric signals.
These are the kinds of musings that can help us postulate about alien life, according to "The Zoologist's Guide to the Galaxy: What Animals on Earth Reveal About Aliens — and Ourselves," by University of Cambridge zoologist Arik Kershenbaum. Humans have been trying to figure out where alien life is and what it might be like for centuries, from Johannes Kepler's science fiction to Harvard professor Avi Loeb's recent book "Extraterrestrial: The First Sign of Intelligent Life Beyond Earth," which argues that a mysterious interstellar object passed through our solar system in 2017. Kershenbaum argues that we can figure out quite a lot about how these aliens would look and act by asking the right questions based on observations of the incredible biodiversity here on Earth.
Kershenbaum has studied wolves in Yellowstone National Park, dolphins in the Red Sea, and small mammals called hyraxes in Israel, and the crux of his argument revolves around his experience as an evolutionary biologist. If we can understand how life evolves here on Earth, we can then ask pertinent questions about how and why creatures on other planets might develop in a certain way. After all, Kershenbaum points out, the laws of physics are constant throughout the universe, so we can view Earth as an "evolutionary testing ground" for realistic solutions to life's problems.
Much of his book is organized around a series of chapters probing at different aspects of animal life on earth. Kershenbaum walks readers through chapters on movement, communication, intelligence, sociality, information, and language, describing why each of these tenets of life evolved, how they evolved, how they present or don't present in humans and other animals, and what we can take from our understanding to postulate what aliens might be like. For example, in his chapter on sociality, he explores the costs and benefits of the development of complex societies on earth, showing how cooperation forms when it's evolutionarily advantageous, and extrapolating a theory that as long as relatedness exists on alien planets, kin selection will drive at least some cooperation in those societies. In other words, if it works for us here, it'll likely work on alien planets. "Teatime with our alien neighbors may be possible after all," he tells us.
After all, says Kershenbaum, aliens might be telekinetic, or all-knowing, or little green men with big heads, but why? Some outcomes are simply not likely, like a hyper-intelligent alien floating through the universe and philosophizing for no reason. Others are quite likely: For example, if a neutrally buoyant alien must move through fluid, then it follows that that alien will evolve fins or some other means of stabilizing itself. Other possibilities raise intriguing questions, fit for a sociologist, about what life might be like in other worlds: For example, could a planet support two linguistic species without one enslaving the other?
Readers might raise an eyebrow at the premise of this book. After all, can we really use what we know about evolution on Earth to extrapolate to the vast unknowable universe? But Kershenbaum cleverly anticipates these potential criticisms. He acknowledges that people might disagree with his assumptions; all he asks is for readers to take away some conclusions about what alien life might be like, based on educated guesses.
Kershenbaum is also quick to second-guess himself or to present alternate conclusions to his theories. For example, some scientists believe that mathematical principles could act as a universal language for communication with alien species — but Kershenbaum also points out that mathematics might look different to aliens, or that aliens might analyze the world through other lenses besides mathematics. He argues that humans evolved language to support our complex society and that languages on other planets would probably evolve for the same reason. He admits, however, that language could evolve for a reason incomprehensible to earthlings. In a later chapter, he even contradicts his main conceit that understanding evolution on Earth will allow us to understand other planets: What if we encountered a planet inhabited by designed artificial organisms, or robots, which could bypass natural selection?
Kershenbaum recognizes that scientists are not the only group that have spent centuries speculating about alien life. He has a healthy respect for the work of science fiction writers, too, and his book is peppered with pop culture references ranging from "Guardians of the Galaxy" to "Arrival." He charmingly refers to "Star Trek: Next Generation" as the "Shakespeare of science fiction." His footnotes feature references to both the Bible and Richard Dawkins. The book also includes photographs and drawings to accentuate his points, of creatures ranging from man o' war to ancient ammonites with delicate tendrils and shells. These features, paired with Kershenbaum's friendly and undidactic tone, make his book readable and approachable.
Ultimately, his goal is to encourage readers to ask the right questions about alien life, even if we can't necessarily land on particular answers. Some of those questions include larger philosophical quandaries: Would aliens share the "human condition" with us, and what exactly is the human condition? What is an animal, what is an alien, what is personhood?
These questions are important, Kershenbaum argues, because of humanity's fraught history of grappling with those very issues regarding animals and other humans here at home. Perhaps, he says in his epilogue, while we wait to find aliens, we can ponder these big questions and apply the answers in new ways right here on Earth.
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Emily Cataneo is a writer and journalist from New England whose work has appeared in Slate, NPR, the Baffler, and Atlas Obscura, among other publications.