“What is life?” isn’t a question most people turn over and over in their heads all day. As David Toomey points out in Weird Life, a brisk, entertaining primer on the search for forms of life that may challenge and extend the common understanding of the term, “philosophers have been formulating definitions of life through much of recorded history. Most have characterized life not according to what it is made of (until the late 19th century, no one had any idea), but according to what it does. And most have come up short.” It’s trickier than it sounds. “For instance, suppose we define a living organism as that which grows, consumes, converts matter into heat energy, maintains a metabolism (that is, perpetuates itself through chemical activity), and after a fashion, dies.” That might sound pretty good, until Toomey notes that it would include stars and candle flames. And trying to close that loophole by adding the requirement that living things reproduce themselves would include crystals in the category of living things, while shutting out mules and worker ants.

For readers who respect and value the idea of science but don’t actually have much technical working knowledge of it, Weird Life is a bracing refresher course in just how slowly the pace of scientific knowledge moves, and how much uncharted ground is still out there. While it can be astounding that scientists know so much about our world, “If we were to learn what they don’t know, we might be just as astounded, for what they don’t know is a great deal,” such as exactly how many species exist on our planet. It wasn’t until the 1940s that marine biologists got a firsthand look at aquatic life “at great depths,” surviving “in total darkness and at enormous pressures… feeding on dead and decaying matter that sank slowly from the waters above.” Throughout the 20th century, scientists discovered things acclimated to environments that had been thought too hot, too cold, too acidic, or just too toxic to support life, from the ocean floor to chemical hot springs.


Having made it plain just how long it has taken human beings to get a sense of some of the basics of life on Earth, Toomey is well-equipped to help readers appreciate just how limitless the unknown possibilities of “weird life” in the universe might be. Much of his book is a clear-eyed examination of the search for extraterrestrial life, or SETI, a project that began in earnest, or at least came in from the fringe, in 1959. That was the year that physicists Giuseppe Cocconi and Philip Morrison published an article in Nature “outlining an in-depth strategy for which radio telescopes might be used to detect the communication of extraterrestrials.” By the time their work was published, an astronomer named Frank Drake had already reached out to the National Radio Astronomy Academy, proposing to monitor the airwaves for possible radio signals from space. Others followed Drake’s lead, yielding half a century’s worth of results that might be called “mixed”: As Toomey summarizes, “more than a few honest mistakes, one hoax, and one possible signal, the last never repeated but still unexplained.”

Even hardened skeptics may feel a bit of a tingle over that “still unexplained.” Unlike many writers covering this turf, Toomey is calm and clear-eyed, but alive to the exciting possibilities that other, perhaps madder writers and thinkers are engaged in sniffing out. He touches on science fiction, including a Star Trek episode where the Enterprise’s crew encounter a silicon-based life form that tries to communicate with Captain Kirk by etching a message—”NO KILL I”—into rock, only to find that its “apparent confusion of nominative and objective case gives them pause.” He also touches on such figures as John Lilly, who popularized the idea of dolphins as beings so intelligent that they should be able to “communicate as equals” with human beings. Lilly struggled to develop a common language for human beings and dolphins to share, but he was ultimately unsuccessful. But like any good, open-minded science-fiction hero, he “came to believe the limitation was on his end.” The special charm of Toomey’s book is that he can appreciate the humor in the absurdity of a quest like Lilly’s while still appreciating the idealism. Toomey is a good man to have watching the skies, and the ocean floor.