I was careful to use the term "lifespan" rather than "life expectancy" to avoid this error. Historically people died mainly of infections or sepsis. Modern medi

I was careful to use the term "lifespan" rather than "life expectancy" to avoid this error. Historically people died mainly of infections or sepsis. Modern medicine has developed treatments for those, so now cancer, heart disease, and dementia -- formerly fairly rare because people would die of something else first -- are the leading causes of death among the elderly. These conditions, which can take years to cause death, require long-term expensive treatment, with very little difference in average lifespan of people who reach adulthood.