Why does hair turn gray?

Why does hair turn gray? Because people continue to insist on having and raising children? Because the hair coloring companies are putting something in our drinking water? It’s a publicity stunt somehow involving Madonna and Michael Jackson?

All of these are plausible, but there’s an easier explanation. You get older. Your body produces less melanin, the substance that gives hair its color. Without that color, your hair becomes transparent. Each hair is hollow, a shaft enclosing a column of air. Without the protective coloring, light can penetrate your hair and be refracted by that air column, producing the white/gray color we associate with aging.

Should you color it? What will you do when you lose that hue?

Source: Just Curious About Animals and Nature, Jeeves (Ask Jeeves) By Jack Mingo and Erin Barrett