Vol 451|17 January 2008 BOOKS & ARTS Twenty-first-century anatomy lesson Polymath pieces together the surprising past of the human body from fins, wings, hangovers and hiccups.

Your Inner Fish: A Journey into the fins, including some wrist bones. And while 3.5-Billion-Year History of the Human Body Shubin and his colleagues were digging up by Neil Shubin Tiktaalik in the Arctic, some of his students Allen Lane/Pantheon: 2008. 240pp. stayed behind in Chicago to find equally use- £20/$24 ful clues about the transition from sea to land in the genes that help build the fins of sharks Carl Zimmer and paddlefish. Six hundred years ago, anatomists were rock Your Inner Fish combines Shubin’s and oth- stars. Their lessons filled open-air amphithea- ers’ discoveries to present a twenty-first-century tres, where the curious public rubbed shoulders anatomy lesson. The simple, passionate writing with medical students. While a surgeon sliced may turn more than a few high-school students open a cadaver, the anatomist, seated above on into aspiring biologists. And it covers a lot of a lofty chair, deciphered the exposed mysteries ground. Shubin inspects our eyeballs, noses of the bones, muscles and organs. and hands to demonstrate how much we have Modern anatomists have retreated from in common with other animals. He notes how the stage to windowless medical-school labs. networks of genes for simple traits can expand They have ceded their public role to geneti- and diversify until they build new complex cists unveiling secrets encrypted in our DNA. structures such as heads. Also, that hangovers Yet anatomists may be poised for a comeback, explain how our ears evolved from sensory cells judging from Your Inner Fish. Neil Shubin, a on the surface of fish. He investigates the hic- biologist and palaeontologist at the University cup, the result of a of Chicago, Illinois, delves into human gristle, tortuous nerv-

interpreting the scars of billions of years of evo- ous system. FIELD MUSEUM WEINSTEIN, SCIENCES OF PHILADELPHIA/J. OF NATURAL ACADEMY DAESCHLER, T. lution that we carry inside our bodies. Some of the I met Shubin ten years ago while writing a case studies book about major transitions in evolution. will be famil- At first glance, his lab suggested a iar to those person who had yet to make up who have read his mind just what kind of a lot about scientist he was going evolution, but to be when he grew most readers will up. Shubin spent find some surprises. much of his I learned that in time studying sharks, the testes sit fossils of mam- near the head. As male human mals and other embryos develop in the womb, creatures he dug their testes gradually descend from that ances- up in places such as tral position to wind up in the scrotum. As they Canada’s Bay of Fundy. He also migrate, they push down on the body wall, cre- stained embryos to learn about Author Neil Shubin (above) discovered the ating a weak spot. It is here that the intestines the mysterious process by which transitional fossil Tiktaalik roseae (below). can slip through during a hernia. limbs develop into fins, legs, wings and hands. Along the way, Shubin offers some striking Actually, Shubin’s mix of research had a focus: A decade later, Shubin has plenty of com- examples of how science works. He did not he wanted to understand how new structures pany. Journals regularly publish reports on the wander in the Arctic hoping to trip over a evolve. How, for example, could the tetrapod synthesis of fossils, genes and embryos. Fossils fossil of a transitional species. He knew from limb arise from lobe-fin fish that had no trace of whales with legs have helped scientists figure previous discoveries exactly which formations of hands or feet? Shubin combined informa- out which genes changed as whale legs gradu- he should look for — mid-Devonian sedimen- tion from both fields to identify the genes that ally disappeared. Tinkering with bat embryos tary deposits. When his colleagues began to changed during these key evolutionary transi- has suggested how their hands stretched into unearth Tiktaalik, a glance at its distinctively tions. In the late 1990s, this ‘integrative biology’ wings. Shubin’s own work on limbs has moved flat skull confirmed that they had found what was radical. It ran counter to the long tradition forward spectacularly. In 2006, he and his col- they had come for. They had learned their of specialization in the field. Other developmen- leagues made international headlines with the anatomy well. ■ tal biologists who had spent decades poring over discovery of the transitional fossil Tiktaalik Carl Zimmer is a science writer based in Guilford, shark embryos did not think of heading off to roseae. This 370-million-year-old fish had Connecticut, and is author of Microcosm: E. coli the mountains to find fossils to study. acquired most of the tetrapod limb in its stout and the New Science of Life.

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