The Great Lifespan Escape

At the time when the lines begin, in the mid-18th century, life expectancy in Europe and the Americas was around 35, where it had been parked for the 225 previous years for which we have data.3 Life expectancy for the world as a whole was 29. These numbers are in the range of expected life spans for most of human history. The life expectancy of hunter-gatherers is around 32.5, and it probably decreased among the peoples who first took up farming because of their starchy diet and the diseases they caught from their livestock and each other. It returned to the low 30s by the Bronze Age, where it stayed put for thousands of years, with small fluctuations across centuries and regions.4 This period in human history may be called the Malthusian Era, when any advance in agriculture or health was quickly canceled by the resulting bulge in population, though “era” is an odd term for 99.9 percent of our species’ existence.

But starting in the 19th century, the world embarked on the Great Escape, the economist Angus Deaton’s term for humanity’s release from its patrimony of poverty, disease, and early death. Life expectancy began to rise, picked up speed in the 20th century, and shows no signs of slowing down. As the economic historian Johan Norberg points out, we tend to think that “we approach death by one year for every year we age, but during the twentieth century, the average person approached death by just seven months for every year they aged.” Thrillingly, the gift of longevity is spreading to all of humankind, including the world’s poorest countries, and at a much faster pace than it did in the rich ones. “Life expectancy in Kenya increased by almost ten years between 2003 and 2013,” Norberg writes. “After having lived, loved and struggled for a whole decade, the average person in Kenya had not lost a single year of their remaining lifetime. Everyone got ten years older, yet death had not come a step closer.”5