CHILDHOOD MORTALITY affects life expectancy numbers. “During the early 1600s in England, life expectancy was only about 35 years, largely because two-thirds of all children died before the age of four. The average life expectancy in Colonial America was under 25 years in the Virginia colony, and in New England about 40% of children failed to reach adulthood. During the Industrial Revolution, the life expectancy of children increased dramatically.”
http://en.m.wikipedia.org/wiki/Life_expectancy