YIF: Chapter 2 Review

January 20 2013, 5:08 PM  by Rinu Daniel

How did the simple fish fin evolve into the unique human arm we have today?

            The overall point of chapter two of Neil Shubin's Your Inner Fish was to show one of the connections between the human body and that of the ancient fish. This chapter helps explain the evolutionary history by first introducing the chapter with Shubin's personal account of dissecting the human body during medical school. From there, the importance and uniqueness of the wrist is made and the chapter unfolds on the expedition to find the fossil of a fish that had both fins and limbs, a clear evolutional transition from fish to man. The chapter talks about how they found fossils that didn't fit the criteria they were looking for, a fin that had the single base bone (the humerus),  then the two bones (the radius and ulna in the human skeleton), and then the many smaller bones. Though they found many bones from the correct time frame, they did not have the right bone structure. The fossil they had finally found to fit the criteria was Tiktaalik, which had a flipper like fin with the human arm bone structure.

            The most interesting concept in this chapter was the fact that in the process of evolution, bone structure evolved before such as fingers. I had always imagined that in the slow evolution from fish to human, the fins would slowly turn into hands and fingers. I hadn't expected it to be possible for a fin/flipper to have the human bone structure inside. Of course, I have limited knowledge on this topic, so my imagination had gone somewhat wild trying to visualize what full evolution must've looked like. But it was still very interesting to realize that I had been wrong, and to learn how things actually worked out. The facts in this chapter seemed to connect towards Big Idea #1 more than any of the others because the chapter is still discussing the evolution of life, and how the author and his team had been looking for a specific fossil. An example of how it connects with Big Idea #1 is how they had found that in fish, specifically in the fins/arms, the single base bone was the first to evolve in the fish fin, with another single bone afterwards, followed by the many small bones. Only afterwards did the two forearm bones evolve, the ulna and radius in the human arm.