Your Inner Fish
Where many popular books about the animal kingdom focus on the differences between, for instance, types of primate behavior, or breeds of dogs, or variations in animal psychology and morphology because of ecological habitat, and so forth, Neil Shubin’s Your Inner Fish focuses on the underlying similarities. As he writes, “When you look into eyes, forget about romance, creation, and the windows into the soul. With their molecules, genes, and tissues derived from microbes, jellyfish, worms, and flies, you see an entire menagerie.”
Shubin is an authority on reconstructing the relationships among prehistoric creatures and those living today. In 2004 he discovered a famous “missing link,” a fossil called Tiktaalik roseae, which excited the worlds of both science and the public upon publication of its description in 2006. This creature is a remarkable intermediate between fishes and land-living animals: Though a fish, living in shallow streams and mud-flats, it had arm and leg bones similar to those of a mammal; it was able to do push-ups.
While Shubin’s autobiographical anecdotes (chiefly about his work as a paleontologist on site) appear in nonlinear order throughout his text, the book is astutely organized. In the first four chapters he shows how various branches of science prove that various organs within various creatures, ancient or extant, are profoundly related. The following chapters enumerate the resemblances between the designs of bodies, heads, hands, noses, eyes, and ears belonging to most of the denizens of the animal kingdom. “There isn’t just a single fish inside of our limbs; there is a whole aquarium.”
Most of the text expounds upon the relationships between unicellular creatures and invertebrates on the one hand and far more complex living forms on the other.
His discussion of the hand (or fin or paw) is exemplary, describing experiments by various genetic researchers who tinkered with a gene (which they comically named Sonic hedgehog after a computer game character) in creatures as different as sharks, chickens, and flies. They discovered that Sonic hedgehog is responsible for shaping appendages, whether shark fins or human hands, and that if its normal function is interfered with, in the laboratory, the result is a surprising reduplication of digits, such as changing a thumb into a pinkie finger or vice versa. The importance of this finding is that the evolution of fish fins into land-based limbs was not based on the emergence of new kinds of DNA, but, rather, that ancient genes merely recombined in new ways.
Shubin’s recollections of his first investigations in the world of fossil-finding under the tutelage of colleague Dr. Farish A. Jenkins are delightful. He jests about his beginner’s inability to distinguish among tooth, bone, and sandy rocks in the Arizona desert. He recalls the electrifying jolt he felt when he first spotted a tiny tooth, “as glorious as the biggest dinosaur in the halls of any museum.” On a 1984 excursion to Nova Scotia, Shubin felt disappointed by his team’s tiny haul, only to find later that he had brought home a rare specimen: a tooth from a fossilized tritheledont, a remarkable creature that is part mammal and part reptile; it might have resembled a mouse with crocodile teeth or, more precisely, a furry lizard with mammalian carnivorous teeth.
Recognizing that his subjects under discussion may be abstruse for some readers, he leavens his scientific jargon with wit, as for instance in his amusing instructions on how to extract DNA in the kitchen, using a piece of steak, salted water, soap, and a few other ingredients. Elsewhere, he remarks jocularly, “The job of teeth is to make bigger creatures into smaller pieces.” Such enjoyable tidbits abound in his book.
Shubin references popular culture frequently for clarity. “For those who believed that skeletons began with jaws, backbones, or body armor, conodonts [extinct animals similar to eels] provide an ’inconvenient...
(The entire section is 1,812 words.)