Wrinkles, and Sun Damaged Skin - Why does it take 20 years to show up? Why does our skin wrinkle more as we age?

Most of the Baby Boomer generation enjoyed having a great tan when they were young. Now 20 to 30 years later the results of that over exposure to the Sun are showing up as wrinkles and sagging skin. Can anything be done to change it? The free radical theory of aging may give us a clue.