In 1601, James Lancaster, an English sea captain, set sail from England to India. Overseeing a crew of 278 sailors on four separate ships, Lancaster conducted an experiment to evaluate the effectiveness of a treatment to prevent scurvy. He administered three tablespoons of lemon juice to the members of his ship and left the crews of the other three ships untreated—effectively creating a control group. Half-way through his journey, Lancaster’s experiment yielded startling evidence: none of the sailors on his ship had died of the disease, but 110 of the sailors—or 40 percent—on the other ships had succumbed to the dreaded malady.


With such clear and compelling evidence, one might have expected the British Navy to begin immediately administering lemon juice to sailors. It did not.


Nearly a century and a half later, in 1747, James Lind, a British Navy physician who was familiar with Lancaster’s work, carried out the first example of a truly controlled clinical nutrition study using human subjects. He prescribed oranges and lemons to scurvy patients and found they were cured in a matter of days. Six years later, in 1753, Lind published his seminal work, “A Treatise of the Scurvy.”


Armed with this new information, one might again have expected the British Navy to make haste in prescribing regular doses of citrus fruits to all of its sailors. Alas, it did not. It took an additional 48 years for the British Navy to wipe out scurvy.


Why did it take the British Navy almost two centuries to adopt a new, albeit simple, method for a treating a disease that could have spared the lives of untold numbers of its sailors?


A variety of factors were at work, but prominent officials and the sailors alike had different ideas for the best way to prevent scurvy and this erroneous knowledge prevented them from being receptive to new knowledge. In short, before they could fully assimilate the new information they had to unlearn their old knowledge.


It is easy to dismiss the scurvy case as an isolated example and chalked it up to poor scientific knowledge; the slow diffusion of new information; bureaucratic inertia or just plain stupidity. Unfortunately, the British Navy isn’t alone in its slowness to unlearn.


Consider the case of Australian physician Barry Marshall. In 1984, Marshall traveled to Brussels, Belgium to a prestigious conference of ulcer specialists to discuss his research which strongly suggested that ulcers were caused by bacteria. His presentation was greeted with laughter because the audience judged the idea so preposterous.


A year later, Marshall returned with even more compelling evidence and this time he was shouted down with a chorus of boos. It took the American Medical Association a decade but it finally recognized his research and announced that the vast majority ulcers were caused by bacteria — and not by acid, stress or spicy foods as leading ulcer experts had so recently argued. In 2005, Marshall and his researcher partner, Dr. Robin Warren, were awarded the Nobel Prize in medicine.


The question is this: Why were ulcer patients treated with unnecessary, costly and often ineffective treatment for more than 20 years?


The answer is because many people, including highly educated medical specialists, have a difficult time unlearning old knowledge.


It would be reassuring to think that society has learned much since 1984 and it won’t repeat similar errors in the future, but we can’t be so sure. In 2007, a study was released suggesting that the manner in which we now treat heart attacks is exactly the wrong thing. This is because, by administering oxygen, we are shocking the remaining healthy heart cells and exacerbating an already lethal situation.


How long will it take medical professionals, paramedics and otherwise well-intentioned CPR-trained citizens to unlearn our current methods for treating heart attack victims?


Unfortunately, our lives are at risk in a multitude of ways because of our inability, unwillingness or slowness to unlearn. What if I told you that six times as many people died in their cars from the terrorist attacks on that fateful day as did all of the victims in the planes that crashed into the World Trade Towers, the Pentagon and in the rural farm field in Pennsylvania—combined!


You probably wouldn’t believe it. However, if you changed your frame of reference and considered that, in the wake of 9-11, millions of Americans decided to forego flying and instead choose to drive to their destination, the numbers become more believable.


Why? Because driving is statistically more risky than flying. In fact, an estimated 1,535 (and counting) more Americans have died in automobile accidents than otherwise would have if only those travelers chosen the safer method of travel – flying. Alas, before people can accept that airplanes are more likely to get them safely to their destination, they first need to unlearn that driving is safer than flying.


Unlearning can not only save your life now, it may also save your life in other ways. Provided that is we have the wisdom to unlearn where the true threats to our safety lurk.


Quick, which is the greater threat to a child’s safety: the neighbor’s pool or the unlocked gun in his closet? By a factor of 50, it is the swimming pool. As a general rule, most of us are awful at assigning realistic levels of risk to everyday activities. To improve our odds of more safely navigating the future, unlearning is a critical skill.


Another case-in-point: Michael Osterholm, one of the world’s leading epidemiologists, travels all over the world arguing that countries and institutions are woefully under-prepared to deal with the possibility of a major pandemic. Interestingly, in his presentation, Osterholm makes the compelling point that as dangerous as the threat of a pandemic is, more people will likely die from non-influenza-related deaths during a pandemic than from the flu itself.


How so you ask? Well, because much of the pharmaceutical industry utilizes “just-in-time” inventory procedures, it is quite possible that in the event of a pandemic major shipping, trucking and distribution centers will be slowed or shut down entirely. As a result, hospitals—many of whom already possess dangerously low supplies of many critical life-saving drugs—will run out of these important drugs in a matter of days. The end result is that just as untold numbers of British sailors perished unnecessarily from scurvy, a similar fate awaits those who are unfortunate enough to be dependent on certain drugs during a global pandemic.


It needn’t be this way. From driving less and flying more, to treating heart attacks differently, to correctly sizing up the threats in your neighborhood, to rethinking our pharmaceutical supply chain, unlearning could, quite literally, be the difference between living and dying.