With its strong emphasis on commonalities with all tetrapods, all animals with heads, all animals with bodies, all living beings — Your Inner Fish, by Neil Shubin is a fascinating book about the structures in our bodies. It’s a little sad that the book has to begin with an argument for evolution. The first chapter strikes me as very dumbed down, as if aimed at a high school audience that thinks they have to be persuaded to believe. Or maybe I was just bored because it all seems so obvious and non-controversial.
Once we get past that, the book is filled with all sorts of Neat Stuff about Living Beings. Everyone’s going to find different favorites. Here’s some of mine.
I enjoyed the story of how the author tells discovered the creature on the cover: Tiktaalik, a fish in transition from water to land, its limbs strong enough to do pushups but it still essentially fins. I loved the passage about how he learned to see fossil teeth in the desert floor. Much like the title essay of Stalking the Wild Asparagus, in which the young Euell Gibbons goes foraging and when he finally spots one asparagus plant, suddenly sees that he is surrounded by it; the young Neil Shubin goes fossil hunting with two experienced geologists, looking and looking until he finally sees a tooth and perceives the difference between fossil and rock.
All of a sudden, the desert floor exploded with bone; where once I had seen only rock, now I was seeing little bits and pieces of fossil everywhere, as if I were wearing a special new pair of glasses and a spotlight was shining on all the different pieces of bone.
I liked the chapter about the cranial nerves, which “have given medical students fits for decades” tangle like an old building’s plumbing, which has been rerouted. The original “plumbing” was the the four arches that form in an embryo. In fish, they become gills. In their descendants as the embryo develops, each arch gives rise to a different part of the head, complete with a nerve and blood vessels, and they’re not in the same places.
The chapter on the inner ear is particularly memorable, discussing not hearing but how our inner ears sense our body position, balance, and motion. How alcohol gets into the gel, disrupting it like an internal lava lamp, giving a false sense of motion. Only after that, he goes back and suggests the inner ear might be evolved from the sensory arches along the lines on a fish’s side that give it the sense of the water’s motion.
I was weirded out to learn that in fish, the gonads develop and remain near the heart. Since mammals need to have them outside the body, where it’s cooler, as the embryo develops, the gonads move. Ovaries descend toward the uterus; testicles descend through the abdominal wall, leaving a weakness. Both leave loopy circuitry trailing behind them.
What I didn’t like was how disordered the whole book seemed. You read about evolution, Tiktaalik, limbs, embryology, hunting fossils, teeth, learning to hunt fossils, embryology, cranial nerves, how embryos become bodies, single-celled life, how bodies hold together, the sense of smell, the structure of the eye, the functions of the inner ear, and the various ills we now are heir to. It’s all entertaining, but you get no sense of direction, as if the book had evolved without a plan. Like, um, us! Some things only have to be good enough to propagate.
So read a copy.