PAIN AND MALAISE

Just as an itch can motivate defensive scratching, pain is an adap- tation that can lead to escape and avoidance. The skin, sensibly enough, is highly sensitive to pain. If it is being damaged, some- thing is clearly wrong, and all other activities should be dropped until the damage is stopped and repair can begin. Other kinds of

pain can also be helpful. While an abstract realization that chewing is impaired because of an abscessed tooth might possibly lead to more chewing with other, unimpaired teeth, the tormenting pain of a toothache far more effectively prevents the pressure on the tooth that would delay healing and spread bacteria. Continued pain from infec- tion or injury is adaptive because continued use of damaged tissue may compromise the effectiveness of other adaptations, such as tis- sue reconstruction and antibody attacks on bacteria. Pain motivates us to escape quickly when our bodies are being damaged, and the memory of the pain teaches us to avoid the same situation in the future.

The simplest way to determine the function of an organ like the thyroid gland is to take it out and then see how the organism mal- functions. The capacity for pain cannot be removed, but very occa- sionally someone is born without it. Such a pain-free life might seem fortunate, but it is not. People who cannot feel pain don’t experience discomfort from staying in the same position for long periods, and the resulting lack of fidgeting impairs the blood supply to the joints, which then deteriorate by adolescence. People who cannot feel pain are nearly all dead by age thirty.