As Elsner reveals, survival in extreme conditions such as those faced by seals is often not about running for cover or coming up for air, but rather about working within the confines of an environment and suppressing normal bodily function. Animals in this withdrawn state display reduced resting metabolic rates and are temporarily less dependent upon customary levels of oxygen. For diving seals--creatures especially well-adapted to prolonged submergence in the ocean's cold depths--such periods of rest lengthen dive endurance. But while human divers share modest, brief adjustments of suppressed metabolism with diving seals, it is the practiced response achieved during deep meditation that is characterized by metabolic rates well below normal levels, sometimes even approaching those of non-exercising diving seals. And the comparison does not end here: hibernating animals, infants during birth, near-drowning victims, and clams at low tide all also display similarly reduced metabolisms.

By investigating these states--and the regulatory functions that help maintain them--across a range of species, Elsner offers suggestive insight into the linked biology of survival and well-being.