Why Ancient Life Expectancy Misleads

Life expectancy is not adjusted for infant mortality; it is simply the average number of years a person is expected to live from birth, so early childhood deaths drag the number down. In past societies, including hunter-gatherer groups, many children died very young, but adults who survived those dangerous early years often lived well beyond 35 or 45. Because of this, the familiar claim that “people only lived to 30 in the old days” mostly reflects high child mortality, not adults suddenly dropping dead in middle age.

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