I have been graying since college, so you'd think I knew all about this, but I don't think I've ever had a gray hair that had black roots. Hairs are gray when the pigment is no longer made or no longer put in the hair. If a gray hair is black at the root, this suggests that the pigments have been added again. Is this possible? Well, other mammals, do it every year. Hares and ermine have white coats in winter. The rest of the year, their coats are brown, with other colors. Clearly the genes for making and/or depositing pigments can be switched on and off. I'm not holding my breath until mine switch back on again!

You can probably figure out why some animals turn white in winter (even if that wouldn't make sense in Goleta), but the ermine keeps a black tip on its tail all year round. Any ideas why? A great experiment was done to test this. As I remember, it involved a black parking lot, a white background (maybe a huge sheet), a stuffed ermine on a motorized cart of some kind, and a trained hawk. Oh yes, sometimes the end of the weasel's tail was white and sometimes it was black. Can you figure out their question and how they answered it?

There is a direct connection between hair pigment and nutrition. For example, starvation can cause your hair to turn red. There is also some evidence that changes in hormone levels, particularly sex hormones (testosterone, estrogen, progesterone, etc.), can cause hair to turn gray.

There is also a link between gray hair and changes in the scalp due to aging. The blood vessels that supply hair roots with nutrients diminish with age, so the root receives less nutrients and may eventually be unable to synthesize hair pigment. This may lead to graying. Also, gray hairs are not all pure gray. Many can be mottled: patches of gray (no pigment) interspersed with patches of color (pigment). This may relate to the current nutritional status or hormone content in the blood at the time that part of the hair shaft is produced.

Lastly, the genes that regulate the production of hair pigments may also be regulated genes, so that the time someone goes gray and the amount, location and appearance of the gray hair may reflect your genes.

If we knew exactly what causes gray hair, you can bet that someone would have already marketed a solution (vitamin supplement, hormone treatment, etc.)!

Researchers are now finding that people who smoke are more likely to start accumulating gray hairs in their 20's and/or have hair that is half-gray by their 40's. The study was conducted by scientists researching bone loss (they noticed a connection between early gray hairs and thinner bones, then linked both of these traits to smoking), but the result is interesting none the less.