The Mammal in the Mirror: Understanding Our Place in the Natural World

"The Barash team builds bodies. They aren't on an exercise regime. Instead, they reveal the ancient and simple roots upon which our bodies and personalities rest. Their aim is to make you "bioliterate" - to gain the ability to understand why there is unity in all life, including ourselves. Their technique examines the mechanisms of DNA, the ubiquitous molecule that extends across the living community. The authors show how DNA's working portions, the genes, act to build organisms, from the minuscule not-quite-alive viruses to complex creatures like us. They structure their presentation into three views "close up, at midrange and from a distance". Each view is dependent on understanding the earlier picture as complexity of the organisms described increases. The Barash father-daughter pair present a highly descriptive and readable account of life's processes and why it's important to us to understand them. They stress that many of the topics reviewed here remain obscure, needing readers to continue the quest they've charted.

Opening their account with a detailed examination of DNA's mechanism for making proteins, the basic process of an organism's structure and life operations. They show how understanding genes provides information on a wide variety of subjects. They examine such diverse topics as DNA "fingerprinting", growth and development and how errant patterns can result in various afflictions - such as "mad cow" disease. They move to the world of viruses, how they are built and propagate - and how the same molecule that allows virus replication to also mount defenses against them. In their discussion, they raise questions about the body's reaction to viral infection - is sneezing or coughing a mechanism these tiny organisms imparted to us in order to help them spread?

From the "recipe for life" molecule of DNA, the Barashes reveal the world of the cell. Where did it come from? Why are there parts of the cell that seem to lead an almost independent existence, while operating within the cell? The authors show how cells have programmed life cycles of their own. They remind us that the cell is "born", goes through a series of steps at varying paces, then "dies". How are cells chosen to build particular parts of the body, giving us individuality while following a basic "standard pattern".? All members of a species look generally alike, yet each is an individual. These minor differences reflect how evolution has tailored life to adapt to change. They remind us that only one type of cell in the body never replicates itself. Muscle cells can shrink or enlarge, but new ones aren't made.

Without doubt, the most informative chapter in the book is on the brain and nervous system. This section emphasises how many of our emotions and other behaviour traits are rooted in the mass of nerve cells within the brain and connecting to the remainder of the body. Unlike the lumpy body cell, the neurons are lengthy whip-like structures designed for rapid interaction with other neurons. Almost like the muscle cell, brain cells rarely replicate. What you attain during the first years of living and developing the brain will remain with you for life. Unlike muscle cells, the brain's neuronal net don't enlarge or contract. Instead, new information may displace or divert older data stored in the neurons. And the brain, of course, is constantly acquiring new information.

Still in the "middle view", the authors examine that great mystery - sex. They explain how the mechanism of reproducing ourselves reaches back to that DNA of the early chapters. "Gene shuffling" has numerous long-term advantages to any species utilising it. This process of mixing genes from two parents provides unique individual offspring - just what natural selection needs to select from. It also contributes to the body's mechanisms for combating infection. In effect, when an egg is fertilised, part of the on-going process is to reprogramme the immune system almost from scratch. The high speed adaptability of infective agents such as viruses is countered by our individuality. It's more than just brown eyes or blue! Finally, the authors look at how the body acquires and utilises energy to keep these processes functioning. Successful energy conversion provides the framework for successful reproduction.

In the final segment, the authors place the human species firmly within the panorama of all Nature. They stress the interconnectedness of all living things. The sharing of DNA is the signal that our role cannot be separated from the remainder of life. The planet runs on an "energy budget" of which we are a significant part. They describe how "food webs" are composed of "trophic levels" - in plain, but undescriptive language - the "food chain". There is, they remind us, much more to food webs than who consumes what. Energy material must be processed through cyclical steps. Interrupting those processes, such as by modifying gas content of the atmosphere or raising ambient temperatures, is dangerous to our species and others. "Everything Touches Everything Else", they remind us. The lesson is that if we don't start to understand life, we won't have it to enjoy. "Dare to know" where you fit in the natural world and understand what roles you may enjoy and which may need to avoid."
~ Written on 2005-02-21