There appear to be striking similarities between the cranial nerves and muscles in both sharks and humans that develop in the third and fourth arches.Neil Shubin. He explains how each of the four arches develops in a manner specific to each species. Here, he makes an interesting comparison between developing shark and human embryos, focusing on the four arches that make up the gill region. From there, Shubin talks about the development of the head. When talking about ostracoderms, which existed about 500 million years ago, Shubin describes them as being “fish look like hamburgers with fleshy tails” (p. The descriptions and illustrations are excellent. Shubin talks of fieldwork in Arizona and Nova Scotia before explaining the molecular composition, development, and use of teeth, which he does in an engaging way with some interesting information. Second, because teeth are harder than bone, they are among the most commonly available fossils. First, the shape and size can provide important information about the diet of creature and clues as to how the animal lived. He points out the importance of teeth to the paleontologist. Shubin looks at an often overlooked piece of anatomy, teeth. He takes a “forest to the tree” approach, starting with limbs and getting progressively smaller, analyzing tissue, cells, and finally genes. Shubin does a fine job keeping the reader interested. This is a brilliant example of homology, that is, similarities in structure across taxa that are due to inheritance by a common ancestor.Ĭhapter 3 discusses genes, an important commonality among related species. The only differences across taxa are the shapes and sizes of the bones and number of blobs and digits. Shubin points out the basic common design shared by all limbed vertebrates: “One bone, followed by two bones, then little blobs, then fingers or toes” (p.
At that point in my mind, there was no doubt that a bat wing was a hand with modified elongated fingers. Although I have seen it illustrated many times, in a variety of textbooks, seeing the actual bones themselves immediately elicited this vision of a spidery, “Nosferatu-” type hand. I remember attending the opening of the Darwin exhibit at the American Museum of Natural History and viewing the bone structure of a bat wing. This is one of the oldest (and strongest) pieces of evidence supporting evolution. My favorite chapter in the book is Chapter 2, which focuses on the similarities of limb structures in various creatures.
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