2019-05-08
An in-depth examination of "the place of human beings in the nearly four-billion-year-long history of life."
Humans are the only creatures that talk, reason, and reflect on who we are, but all organisms do many of the same things we do to survive, writes LeDoux (Science and Psychiatry/New York Univ.; Anxious: Using the Brain To Understand and Treat Fear and Anxiety, 2015, etc.). Plenty of popular authors describe the history of life, but LeDoux wants readers to remember as well as enjoy, so he divides his book into short, pithy chapters, each explaining a single evolutionary advance. Four billion years ago, something acquired the ability to extract energy from its surroundings and to reproduce, so it fit the definition of "life." To continue living, it had to survive by avoiding dangers and pursuing necessities. The author emphasizes that action and even learning and memory don't require a nervous system. "Behavior is not…primarily a tool of the mind but of survival," he writes, continuing, "the connection of behavior to mental life, like mental life itself, is an evolutionary afterthought." Creatures without nerves did fine for several billion years. Primitive hydra evolved a simple nerve net that enabled much quicker responses, but since the net was generalized, hydra behavior is identical no matter what part of its body is stimulated. Its close kin, jellyfish, developed the first concentrated collections of neurons to control specialized actions such as swimming and prey capture. Nervous systems and then brains gradually grow more complicated, and LeDoux delves into the nature of awareness, perception, deliberation, memory, language, emotion, and, finally, consciousness. Like all good educators, the author begins simply. The first half of the book is a superb overview of evolution; the second half gradually focuses on brain structure and function. Readers will learn a great deal of deep neuroscience, although, despite a generous stream of illustrations, they will need to pay close attention.
A dense but expert history of human behavior beginning at the beginning.
