Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body by Neil Shubin (Pantheon: 2008. 230 pp.)
“The best road maps to human bodies lie in the bodies of other animals,” says author Neil Shubin, a paleontologist from the University of Chicago. That sums up why, through unusual circumstances, the fossil hunter who studies how limbs evolved was tagged to teach human anatomy to the school’s medical students.
In 2006, the year after he began teaching the course, Shubin and his research team hit pay dirt when they discovered a 375-million-year-old fossilized fish in the Arctic. Naming it Tiktaalik, it is the earliest example of an intermediate animal with limbs and wrists, designating it as a species in transition from water to land. This pivotal discovery, along with his time spent dissecting cadavers, triggered an epiphany in Shubin. It crystallized how the inner workings of the human body are directly inspired by these early fish.
Shubin transformed his enlightenment into “Your Inner Fish,” in which he incorporates evidence from fossils, genes and today’s living species to show how scientists have pieced together human history. By the end of the book, it makes sense how and why the human body works the way it does.
Using humor and embracing a kind of star-struck awe of nature’s inventiveness, Shubin’s easy-to-read book delves into prehuman evolutionary history and then travels forward to chronicle our development. He recounts the story behind the Tiktaalik expedition, including entertaining anecdotes of how he learned to become a fossil hunter and how geology is used to best guess locations of productive digs. Because studying how limbs evolve requires more than field work, Shubin goes into the lab to explain how he uses the critical tools of molecular biology to unearth more information.
By applying genetics techniques, Shubin demonstrated that reptiles, birds and mammals descended from fish ancestors, even though the former all have limbs. His discovery that fish use the same genes to make fins that mammals use to make limbs means that new genes were not required to transition from fins to limbs; the existing genes just needed to be used in different ways. Putting this into the bigger picture means that all the planet’s inhabitants must be mere variations on the same theme. How profound!
Now that we are here, what do billions of years of human evolutionary history mean for our lives today? Shubin reiterates that because we are jury-rigged versions of early life forms, we harbor weaknesses we could have avoided had we been put together from a blueprint dedicated to making only us. For instance, those annoying hiccups are the result of a convoluted nervous system that makes sense only for fish and tadpoles. Men are prone to hernias because of our shark relatives, which have their testes in their chest region, right behind the gills. At some point in evolution, the testes started moving downward, leading to an anatomical compromise that makes a weak spot around the groin.
Because of the many aspects of this book, different information will resonate with each reader, making this a book club selection guaranteed to elicit lively discussion. As to complaints, I only wish Shubin had clarified that humans are not the pinnacle of evolutionary progress. While I appreciate that the book’s focus is centered on humans, it is still essential to emphasize that modern lower animals have branched out in their own ways from our prehistoric ancestors and are just as evolved as we are. It needs to be stressed that the whole point of evolution is not solely to create us and be done. Humans are not superior, just one of many lines of evolutionary innovation.
” Judith Lea Garfield, biologist and underwater photographer, has authored two natural history books about the underwater park off La Jolla Cove and La Jolla Shores. www.judith.garfield.org. Questions, comments or suggestions? Email [email protected].