Book Review -- Life's Edge by Carl Zimmer
Life’s Edge sets itself one of the Big Questions – what is life? Predictably, the answer is unsatisfying, but the trip is worth the time. Zimmer started his career at Discover and writes a weekly science column for the NY Times – his credentials as a science communicator are impeccable. The writing shows the influence of a career in mass market publications; it is easy to read, simple, direct, and occasionally so simple it’s irritating. You will not have to “plow through” the book.
Life’s Edge addresses two problems – the first problem is on the human scale, when does life start, and when does it end? The heart-wrenching topics of abortion and end-of-life are right up front. The second problem, more curious, less heart-wrenching, and altogether more amusing, involves which biological systems are living. This takes us on a tour of clearly living things that have varying degrees of stasis (pythons between feedings, bats hibernating). I did not expect an answer to the Big Question, but the detours into very unusual adaptations are quite fun. We live on a strange and wonderful planet.
Zimmer brings some history – after van Leeuwenhoek invented the microscope, there were vigorous debates about life, about spontaneous generation, and Frankenstein’s monster-ish ideas. Mary Shelley was up on the latest speculation when she told the story. Some time is spent with the mystery of how life began – and the camps of “this is a mystery we can figure out” and “it’s God’s mystery and we should stay out of it.” That debate has evolved (pardon) but continues.
The slime molds, which can solve problems and go through mazes, are my favorite part. There is no question they are alive when spreading on our yards (8 kinds of slime molds live in my area) but are they alive as spores? Are viruses alive? They can’t reproduce independently; many say they are not alive. So what are they?
Zimmer presents the NASA definition of life “Life is a self-sustained chemical system capable of undergoing Darwinian evolution” – as an attempted answer to the question, in NASA’s case thinking about how we will know life on other planets. The NASA definition is then challenged with a series of “what abouts” to which there are no good answers.
Carol Cleland’s ideas are next, and for Cleland, the best answer to “what is life” is – “definitions are not helpful until you know more.” Her illuminating analogy is the definition of water – before science had the concepts of hydrogen, oxygen, and bonding (covalent, ionic, hydrogen, van der Waals), defining water was impossible. They drew up lists of attributes, debated ice, and solutions of one thing and another (remember, they didn’t know it was 0.5 M HNO3, not water), and got really tangled. We are, she argues, in this space regarding life. We need to understand more to be able to define it. I might try to find one or more of her books through Interlibrary Loan. Her work is not likely to be as easy a read as Life’s Edge, as it was written by a philosopher and a scholar, not a science communicator.
In the interest of understanding more, so we can someday define life, Zimmer walks us through a series of experiments to create organic molecules from minerals and energy (it does happen) and the discovery of organic molecules on asteroids (it happens in other places too). There are quite a few other laboratory experiments that delve into this or that aspect of what we think of as “living” and the author’s observations and conversations with the scientists designing and executing them is an engaging part of the book.
Life’s Edge is a good read – for the journey rather than the destination. We live in a crazy wonderful place full of very odd biological systems (here I duck the words “living things” and “plants and animals”). Enjoy the trip!
Life’s Edge, the Search for What it Means to be Alive, Carl Zimmer, 2021, Dutton, an imprint of Random House LLC. It is readily available for sale, both in print and as an audio recording. The copy I read came from a NH public library, as part of a popular science book group organized by the Derry, NH public library.