Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body

In his 2008 book Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body, paleontologist and biologist Neil Shubin explores the evolutionary history of various anatomical structures. As Shubin explores the histories of everything from our limbs to our eyes and ears, he shows how closely related humans are to all of Earth’s living creatures.

The first two chapters of Your Inner Fish describe one of Shubin’s most important scientific contributions: the discovery of the fossil Tiktaalik, an ancient fish that lived around 375 million years ago. Tiktaalik is significant because it provides insight into how ancient fish evolved to walk on land.

Chapter 1 takes place during the 1990s, when Shubin discovers the fossil of an ancient fish fin that appears to contain the structure of a shoulder bone. Hoping to find a fully preserved specimen, Shubin plans an expedition to an area of the Arctic likely to contain the desired fossil. Though the first expedition proves fruitless, Shubin finally discovers the fossil of Tiktaalik during a 2004 expedition. Chapter 2 shows how the ancient Tiktaalik provides information about human bodies—in particular, our limbs. Though Tiktaalik is a fish, it contains the bone structure of an animal limb embedded within its fin.