Excerpt from The Wild Life of Our Bodies by Rob Dunn, plus links to reviews, author biography & more

Bakhul's story has lived on through the writing of Jim Corbett, the great hunter of man-eating animals. It was Corbett who would eventually come to try to find Bakhul and then to kill the tiger. The longer story of humans and predators, though, is embedded in our bodies, in our genes and their products, in particular in a network of ancient cells in our brains called the amygdala. The amygdala is connected to both the more ancient and the more modern parts of our brains. It, along with the adrenal system, is caught halfway between our deep past and the present. From there, it urges us into action or contemplation, depending on the circumstances. If you feel any eagerness on behalf of Bakhul, any modest restlessness for resolution of her story, an interest that perhaps even sent a chill or two down your arms, it was because of your amygdala and its signals. But more generally, it was because you are descended from a long line of individuals who escaped being eaten, at least long enough to mate, a lineage going back not just to grandma but to lizards and then even further. Your heart pounds harder when you are afraid (or angry, a point to which we will return) because of the pulleys and levers of your adrenal glands and the signals sent from your amygdala to your brain stem, that even more primitive root of our actions and wants. This system, sometimes called the fear module, evolved primarily to help us deal with predators, whether by flight or, less often, at least historically, fight, but it's a finicky system that can be aroused at the mere idea of a threat. Fear, or at least the urge that precedes it, may even be our default reaction to our surroundings. Some elements of our amygdalae appear to constantly send out signals to our bodies that we are afraid. Most of the time, other parts of the amygdala suppress those signals. But when we see, hear, or experience something that triggers fear, the suppression is released and fear courses through us, instantly, like a bomb in our brain.

Excerpted from The Wild Life of Our Bodies by Rob Dunn. Copyright © 2011 by Rob Dunn. Excerpted by permission of Harper. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.