Enlightenment Now: The Case for Reason, Science, Humanism, and Progress

Figure 5-1, a plot from Max Roser of life expectancy over the centuries, displays a general pattern in world history. 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.

Figure 5-1: Life expectancy, 1771–2015

Sources:Our World in Data, Roser 2016n, based on data from Riley 2005 for the years before 2000 and from the World Health Organization and the World Bank for the subsequent years. Updated with data provided by Max Roser.

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

As a result, inequality in life expectancy, which opened up during the Great Escape when a few fortunate countries broke away from the pack, is shrinking as the rest catch up. In 1800, no country in the world had a life expectancy above 40. By 1950, it had grown to around 60 in Europe and the Americas, leaving Africa and Asia far behind. But since then Asia has shot up at twice the European rate, and Africa at one and a half times the rate. An African born today can expect to live as long as a person born in the Americas in 1950 or in Europe in the 1930s. The average would have been longer still were it not for the calamity of AIDS, which caused the terrible trough in the 1990s before antiretroviral drugs started to bring it under control.

The African AIDS dip is a reminder that progress is not an escalator that inexorably raises the well-being of every human everywhere all the time. That would be magic, and progress is an outcome not of magic but of problem-solving. Problems are inevitable, and at times particular sectors of humanity have suffered terrible setbacks. In addition to the African AIDS epidemic, longevity went into reverse for young adults worldwide during the Spanish flu pandemic of 1918–19 and for middle-aged, non-college-educated, non-Hispanic white Americans in the early 21st century.⁶ But problems are solvable, and the fact that longevity continues to increase in every other Western demographic means that solutions to the problems facing this one exist as well.

Average life spans are stretched the most by decreases in infant and child mortality, both because children are fragile and because the death of a child brings down the average more than the death of a 60-year-old. Figure 5-2 shows what has happened to child mortality since the Age of Enlightenment in five countries that are more or less representative of their continents.