Editor's note: Dr. Charles Raison, CNNHealth's mental health expert, is an associate professor of psychiatry at the University of Arizona in Tucson.
(CNN) -- Humans evolved in a dangerous world.
Because of this, our brains and bodies are wired to be overly sensitive to threats. This phenomenon is often referred to as the "smoke alarm" principle, based on the idea that it is better to be awakened 10 times in the middle of the night by a false alarm than to sleep blissfully just once while your house burns down around you.
However, not all threats are created equal when it comes to activating "smoke alarm" pathways in the brain and body that evolved to help us cope with environmental dangers.
The sad paradox is, we grossly underestimate the danger of many new things in our environment that have not existed long enough to burn fear of them into our genes, while grossly overestimating the danger of other things in the modern world that, while far less dangerous, tap into ancient evolved terrors.
For instance, people have been running for at least a million years and have been gathering in groups to celebrate athletic prowess for least that long. People have been killing each other for far longer than that.
So, sadly, the tragedy of the Boston Marathon bombing could not be better designed to frighten the hell out of us. And as we all know from the aftermath of September 11, 2001, when we get scared enough, we are willing to do almost anything to reestablish a sense that we are safe -- even if this means giving up things we love.
Terrorists are experts at tapping into ancient terrors. They don't spend their efforts convincing us to drive faster, smoke cigarettes or eat more processed food, which are the real killers in the modern world.
No, they commit acts that frighten us so unrealistically that we as a society change our behavior in ways that are profoundly out of proportion to the actual risks involved.
While I certainly advocate reasonable caution, I also want to encourage us not to fall victim to the mismatch between our evolved, and overwhelming, emotional reaction to certain types of events and their actual risk in the modern world.
Terrorists appropriate this mismatch for their benefit. Getting smart about it is a way we can fight back.
A first step toward getting wiser about how we react to events like the Boston bombing is to recognize that we evolved to overreact to these types of dangers, and that therefore we should not immediately change how we live our lives based on these reactions.
Significant scientific evidence suggests that these types of reactions were far more adaptive in the past than they are now, because they more closely fit the realities of ancient environments than those of the modern world.
One way to see this more clearly is to consider dangers that we did not evolve to fear and so grossly underestimate.
Consider, for example, that prior to the 19th century, no human traveled faster than the speed a horse can gallop (30 miles an hour) unless he or she was falling from a height. This explains why most of us fear flying far more than driving, even though driving is far more dangerous. Genes for fearing heights promoted survival over millions of years. Genes for fearing speed were worthless.
Hence, our very different attitude toward highway deaths than airplane crashes or terrorist bombings. Indeed, Mothers Against Drunk Driving (MADD) celebrated a bit in 2012 when 9,878 people died in alcohol-related traffic accidents the previous year; it was the first time in the organization's existence the number had fallen below 10,000.
Bombings, school shootings and other atrocities are horrendous and reprehensible. They enrage us and they break our hearts. This is as it should be.
But if we set aside our evolved passionate hearts and look at the situation in a spirit of cool calculation, changing one's life to reduce the risk of injury from these events is misspent effort.
If you want to protect your children, don't stop taking them to watch marathons. Make sure they are buckled into a car seat and work to stop drunk driving. On average, 1,500 children a year are killed in motor vehicle accidents, and about 31% of fatal crashes involved alcohol. Work to reduce more pedestrian forms of childhood tragedy -- such as abuse and neglect -- which reduce adult lifespan by up to a decade.
We can keep ourselves and others safe by calling police if we see something suspicious at an event.
But if we give up marathons, celebrations, parades and other events without metal detectors and police dogs, we will have lost far more than we will have won, for we will have done precious little to increase the safety of average citizens while at the same time depriving them of one of a free society's greatest gifts.