Biology in the 20th Century stands on three great discoveries of the 19th--that organisms act to maintain a constant internal environment, that species evolve by natural selection, and that parents pass genetic information to their progeny in an orderly, if chancy, manner. In the last 35 years, biologists and chemists have fleshed out these principles into a detailed understanding of the molecular machinery of life. Biology, some say, has thereby entered a golden age, in which all life's mysteries seem about to be laid bare. Biologists have even become the designers of new (and patentable) life forms--bacteria that save strawberries from frost, crops that need no weeding, and transgenic pigs with low-fat pork.
Only the study of the brain has so far partly resisted reduction to the molecular articulation of general principles. Some of the brain's privilege comes from its complexity: As Sir John Eccles put it, "The brain is so complicated that it staggers its own imagination." But complexity cannot long deter the progress of science, especially in an age of supercomputers. The question biologists increasingly face is whether the brain and the mind can--\o7 in principle\f7 --be understood in biological terms. The brain thus represents the ultimate challenge, the Everest, of reductionism.
Like other neuroscientists, Robert Ornstein and David Sobel see the brain as a homeostatic organ, the control center of self-regulation. They begin their provocative and well-argued book with the unexceptionable but powerful statement, "The brain minds the body." By this they mean that the brain coordinates external and internal worlds.
Not only does the brain regulate the temperature and chemistry of the body in the face of changing environment, but it also organizes the body's response to threats and opportunities. Thus Ornstein and Sobel give credit to the brain, rather than to medical progress, for resistance to disease. Yes, streptomycin effectively exterminated tuberculosis, but the incidence of tuberculosis had already declined 97% before the introduction of the antibiotic. Better nutrition probably made the difference, as well as improved hygiene.
According to Ornstein and Sobel, medical progress as such has played only a small part in increasing life span. Most of our increased longevity in the 20th Century comes from the reduction of infant mortality and the diseases of childhood. Despite the advent of microsurgery, organ transplants, antibiotics, and beta-blockers, the life expectancy of a 45-year-old man in the United States today is only three years more than his great-great-grandfather a century ago. Our long life span compared to other species comes from our greater adaptability, due largely to our marvelous brains.
The brain furthers the organism's ability to survive by translating information about the outside world into electrical and chemical signals that direct a stabilizing response. The adaptive contributions of the brain make it susceptible to natural selection. The brain, then, like the other organs of the body, is the product of evolution.
The adaptive significance of the brain is not limited to its more mechanical functions. Even the capacities of the brain that we usually call mind--thoughts, beliefs, relationships, and hopes--contribute to self-regulation and self-preservation. Hearing an intruder late at night immediately triggers a "fight or flight" response, mobilizing muscle, brain, liver, and heart. The thoughtful realization that the intruder is merely a late-arriving house guest turns off the internal alarm. Both responses, first to the nocturnal noise and then to the calming thought, depend on the brain to process information and to convert it to chemical signals.
As brain science progresses, we are more able to understand the mechanisms that connect higher processes to conventional biochemistry and physiology. People have long known that emotions influence performance and survival. Life expectancy is enhanced by social connectedness, to a spouse, a community, or even to a pet. Laughter, tears, and anger also contribute to survival, even in the face of terminal cancer. While detailed mechanisms are unknown, we realize more and more that the brain processes feelings into chemicals, using its own internal pharmacy. Over hundreds of millions of years, the brain's prescriptions have evolved to increase survival. As Norman Cousins has put it, "The human body is its own best apothecary."
Among the most fascinating of these internal drugs are the endorphins ("\o7 endog\f7 enous m\o7 orphines\f7 "), discovered in the 1970s as brain chemicals that mimicked the actions of morphine, opium, and heroin. Endorphins are part of a system of intrinsic pain relief. The system functions in times of stress, danger, and pain. Amazingly, the brain also releases endorphins in response to perceived but not actual external relief, for example, when a toothache sufferer is given a sugar pill placebo instead of aspirin.