In a smooth transition from chapters two to three, Neil Shubin furthered the search for "our inner fish" by going one step deeper into the body, from bone structure to the cells and proteins in charge of building our hands. To explain this concept, some background is included, debriefing a short history lesson in how researchers and scientists found out parts of the DNA especially looking into what makes our pinkies look so different from our thumbs. Work of Edgar Zwilling, John Edwards, and Mary Gasseling led to the discovery of ZPA, a patch of tissue that is responsible for the pinky side of a hand to look different from the thumb side. Years later, Andy MacMahon, Phil Ingham, and Cliff Tabin discovered the set of genes that controlled the ZPA, called hedgehog. The overall point to this chapter is to show that the human relationship with fish are not just bone deep, but can go all the way down the our cells. This hedgehog gene was found in all animals, proving that at some point we all came from one. It helps explain the evolutionary history of humans by showing how we all share the same gene.
I thought that the most interesting concept of this chapter was that a single gene is the reason for how our hands look, and when its location is changed just slightly, suddenly our hands would have a mirror image of fingers. It just seems so weird and cool to me at the same time that the digits would be a perfect mirror image. I had always imagined that, if there had been a case such as this, the other set of fingers would still look like fingers, but would not be a perfect mirror image, maybe just digits of different lengths. Though this book is mainly about evolution, I feel that the facts, thoughts, and ideas of this chapter connect more towards Big Idea #3. I believe this because this idea
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