I consider myself an honest person, almost to a fault. So the next morning, I went back to the store to pay for the jar, where I summoned the young associate manning customer service to explain what happened, probably ad nauseam, as his expression turned to bewilderment or stupefaction when I related how it was all a purely innocent mistake that I wanted to rectify. His face went blank when I asked if I could have the senior discount on the price, $3.80, especially since I thought it shouldn’t cost more than 50 cents.

The odds of humans being dealt the medical equivalent of a royal flush—eliminating disease and slowing or stopping the aging process—may not be as long as we’ve been made to believe, according to scientists.Some futurists think even more radical changes are in the offing: That humans will be able to use technology to solve “the problem of dying.”How did humans go from living an average of 35 years two centuries ago to contemplating living a century or more?