The first forms of anesthetics, for example, didn't emerge until the mid-1800s. But in less than the 200 years since, "things have changed beyond recognition," writes Yuval Harari in his best-selling book, "Sapiens." "Pills, injections and sophisticated operations save us from a spate of illnesses and injuries that once dealt an inescapable death sentence," he writes. "They also protect us against countless daily aches and ailments, which pre-modern people simply accepted as part of life." The average life expectancy since the 1800s has jumped between 25 and 40 years--to about 80 years in the developed world and about 70 years worldwide.