What is the smoke-detector principle in Darwinian medicine?

In Darwinian medicine, the smoke-detector principle explains why the human body frequently expresses protective responses—such as pain, fever, or anxiety—even when they may not be strictly necessary.1

The principle draws an analogy to a household smoke detector: just as a homeowner accepts the minor nuisance of a false alarm caused by burnt toast to ensure they are alerted to a potentially catastrophic fire, natural selection has shaped human defense mechanisms to be highly sensitive. Because the cost of failing to trigger a defense when a genuine threat exists is often far greater than the cost of a "false alarm," the body is evolutionarily designed to err on the side of caution. Consequently, many symptoms that appear excessive are actually normal, adaptive responses that can often be safely blocked by medication without compromising the body's overall protective strategy.1