In chapter 10 of “At the Water’s Edge”, Carl Zimmer explores the macroevolution of whales and tetrapods. In less than 15 million years a hoofed land mammal evolved into the whale, and a lobe-fin evolved into a sturdy-limbed, tetrapod with no gills. Both whales and early tetrapod evolution began with animals exploring the edges of a new ecosystem; the costal wetlands of the Devonain or the shores of the shallow, Tethys Sea. New adaptations arose, allowing those animals to better survive in those conditions. Zimmer used the analogy of an X to illustrate the origins of the first tetrapod and whales and their similarities and differences. Mesonychidlike ancestors of the whale are on the top left tip and lobe-fins are at the bottom left tip. Both ancestors evolved along their axis to their current respective habitats. At the middle of the X Acanthostega and Amulocetus crossed paths. They were surprisingly similar; both animals hunted in shallow water, had long flat heads with snapping jaws, short limbs and strong tails. Farther along, the whale Dorudon is similar to the lobe-fin Eusthenopteron. There is also a debate between scientists about whether the evolution of whales and tetrapods occurred gradually or by punctuated equilibrium. It seems that some changes happen rapidly, while others happen more slowly.

Both “At the Water’s Edge” and “Endless Forms Most Beautiful”, were interesting to read. Carroll’s book had an Evo Devo opinion on development and talked mostly about how genes produced animals and they were responsible for their characteristics. Zimmer gave more of a history of the evolution of animals, in particular tetrapods and whales. The books tied into lecture and expanded on the ideas we were learning about, as well as introduce new ideas that helped give a good overall perspective on developmental biology. I learned a lot from both these books. I enjoyed talking about them in class discussion and it was very useful to write a summary each week and read other students’ summaries. I liked Zimmer’s book better since it was more of a story and he is a better writer than Carroll. I knew that whales evolved from a land mammal but it was really interesting to read the entire story. I would recommend keeping these books in class.