Chapters 8 -11

Chapter 8, which focused on our sense of smell, was straight-forward and interesting. Shubin's analogy of smell to a musical chord made it easy to understand how an odor is the outcome of several receptors sending signals to the brain. I found it surprising to learn that nearly 3% of the entire genome is devoted to identifying various smells, buts so many of these genes are virtually useless. I always wondered why dogs had a better sense of smell than humans even though we are both mammals. Now, I know that humans have traded vision for smell.

Chapter 9 explained the inner workings of the eye. I was stunned when I found out that almost 70% of a human's sensory cells are light-sensing cells. This just shows how vital vision is to us. I thought that Gehring's experiment with the eyeless gene in flies was interesting. Wherever this gene was turned on, a new eye would appear, even at such unusual places like the fly's antenna. Overall, Shubin's explanation of the human eye was intriguing, and I found out a lot I didn't know before.

Chapter 10, which was all about ears, was also very informative. I thought it was interesting that the middle ear bones of a mammal (the malleus and incus) are the same a parts of the jaw of a reptile. Shubin explains how the bones from a reptile's jaw got smaller and eventually evolved into the middle ear of a mammal. It's amazing how evolution works. Shubin also explains how the connection between humans and sharks is revealed by looking at our inner ears. I thought this was very strange since sharks don't even have ears. Humans have an inner ear gel that gives us a sense of acceleration/motion; sharks also share this ability.

In Chapter 11, Shubin eloquently summed up the book's contents. He began by introducing the hypothetical family tree of the "bozos." This example really helped me understand the chapter's late contents. Because we are descendants that have undergone modification, humans still have significant parts inside us that resemble our "tree of life." I was amazed to learn that the top reasons for death among humans are due to our genetic basis. As Shubin put it, we have a "body built for an active animal but the lifestyle of a spud."

I always knew that humans were connected to other living things, but Shubin elaborated on how we are all connected, not just in these chapters, but in the entire novel. This book, as a whole, was highly informative, reader-friendly, and captivating; it renewed my interest in biology.

- Aarti Kumar