It all has to do with health. In Colorado today the life expectancy for a baby is 72 to 78 years. Life span is how long we are designed to live. According to all the different theories of aging it appears that we are designed to live 115 to 125 years.
Simple maturation refers to normal growth.
A five year old looks different from a ten year old. Both can be perfectly healthy but the ten year old has matured. However, we don't know what the 120 year old would look like because of the other kind of aging. This is the age the Dietary Guidelines were written for. The Dietary Guidelines for Americans Eat a variety of foods.