Life expectancy at birth in Sweden jumped from 30 to over 80 years. Even surviving to age 15 added 26 more years of expectation. Hunter-gatherers reaching 45 expected only 14-24 more years versus 40 today. Mortality at age 30 for women dropped 33-fold from 1750s to 1990s. Survival from age 10 to 70 rose from 1 in 3 to 90%. Fewer than half of 18th-century females survived to 60 even after age 20. Median female lifetime increased from under 40 to 87 years. 95th percentile lifespan grew from 81 to 99 years. Mode age of death for adults shifted from 70 to 90. Infant mortality caused 34% of total life expectancy gain since 1751. Ages 0-4 caused 53% but ages 20+ caused 32-35%. Infectious diseases like smallpox, TB, cholera killed most adults historically. Sanitation slashed waterborne killers like dysentery and typhoid. Vaccines eradicated smallpox and curbed measles. Antibiotics crushed TB and cut stillbirths in 1930s. Midwife training and handwashing reduced maternal deaths. Historical mathematicians often died before 50 from infections. Prehistoric remains show few old adults. Western countries mirror Sweden's trends since 1900.