I enjoyed reading Metazoa by Peter Godfrey-Smith. This book discusses the key features of metazoan evolution and simultaneously details the development of the brain and consciousness through these different organisms. The book follows a rough chronology from the simplest organisms to humans, focusing on key exemplars at each step. It begins with simple unicellular organisms and then moves on to corals. I thought it was interesting to learn about how gated channels and basic neurons work. I also enjoyed the comparison between voltage-gated channels and transistors, both of which are fundamental to switching and circuits.
The first metazoan organism that the book focuses on is the shrimp, a representative arthropod. I found it interesting how these organisms combine sensing, thinking, and motion with their many appendages – similar to a Swiss army knife with so many different appendages to do things. After arthropods, the book focuses on the octopus, which the author claims is the most intelligent invertebrate. The octopus is different from arthropods as it does not have a hard exoskeleton, but it does have many different limbs that can move in all sorts of ways, requiring a lot of brainpower. I found it fascinating that, in a sense, octopuses might have many different brains: one in each arm acting independently from their central brain in their head or perhaps acting together collectively.
The book then describes fish, with the kingfish as an example, demonstrating centralization of the nervous system and a great amount of sensing through the eyes and lateral lines. The unfortunate thing for fish is that they don't have many limbs to control with their intelligent brains. Many usable limbs do not appear in vertebrates until the ascent to land, which the book goes through in detail. I was struck by how much more energy is available on land than underwater. As in the sea, the book describes arthropods leading the way onto land, singling out bees, in particular.
The rest of the book follows the usual progression from reptiles and dinosaurs to mammals, focusing on well-known key attributes such as endothermy. I was quite interested in the discussion about potential future development for humans -- where we are going, with further development of our minds and consciousness. Overall, I found this a fascinating book that provided a good sense of evolution and neuroscience at the same time.
Metazoa: Animal Life and the Birth of the Mind
