Crow’s feet – those tell-tale wrinkles at the outer edges of the eyes – used to be a sign of latter middle-age. But as we can see in those candid, unretouched photos shot by paparazzi, younger stars like Jennifer Aniston and Jessica Simpson are already showing signs of crinkly eyes. What gives?

Dermatologists say that the number one cause of wrinkles is genetics. If your ancestors had lovely, baby’s-bottom-smooth skin, you’ll be able to get away with a certain amount of sun exposure and smoking with no ill facial effects. But environment and lifestyle are also important factors, and in Hollywood, both are experienced in the extreme. Many celebs spend hours per day under bright lights and reflexively end up squinting. They also need to be “seen” at the trendiest clubs in the wee hours of the morning, so constant lack of sleep is another factor, not to mention cigarette smoke. Unfortunately, some celebs still rely on Ol’ Sol to give them that glowing tan, rather than artificial bronzers, which is another cause of wrinkles.

And, in a delicious Catch-22 scenario, the Hollywood trend of anorexic thinness has exacerbated facial aging. Celebrities need to be reed-thin to snag acting and modeling roles, but that lack of fat makes the face look gaunt and reduces the elasticity of the skin. Ironically, a small layer of pudge beneath the skin is a vital ingredient when it comes to a youthful face.