The Biology of Human Survival: Life and Death in Extreme Environments

A wonderful opportunity to illustrate the rich complexity of biological responses to natural environments arises when a difference is encountered between acclimation to a single stressor in an environment and overall acclimatization. This biological complexity can be conceptualized in a scientifically useful way. The key concept is based on the hypothesis that acclimation to a single stressor triggers a general pattern of responses that could augment or interfere with acclimation to a second, independent stressor. The name given to this process is cross-acclimation, which is defined as the influence of earlier adaptation to one stressor on subsequent adaptation to a new environment that may or may not contain the initial stressor.

Cross-acclimation demonstrates the importance of the interplay among different stressors that influence the integrated, or overall, response to a complex environment. To complicate the issue a little further, cross-acclimation may result in either positive or negative acclimatization to a new environment. For example, earlier adaptation to cold may help an animal survive a subsequent exposure to ionizing radiation, but it interferes with its ability to survive a lack of oxygen. In addition,

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