first few grey hairs?

Interesting, but not really helpful...

Dr. Desmond Tobin, professor of cell biology from the University of Bradford in England, suggests that the hair follicle has a “melanogentic clock” which slows down or stops melanocyte activity, thus decreasing the pigment our hair receives. This occurs just before the hair is preparing to fall out or shed, so the roots always look pale.

Moreover, Dr. Tobin suggests that hair turns gray because of age and genetics, in that genes regulate the exhaustion of the pigmentary potential of each individual hair follicle. This occurs at different rates in different hair follicles. For some people it occurs rapidly, while in others it occurs slowly over several decades.

In a February 2005 Science article (Nishimura, et al.) Harvard scientists proposed that a failure of melanocyte stem cells (MSC) to maintain the production of melanocytes could cause the graying of hair. This failure of MSC maintenance may result in the breakdown of signals that produce hair color.

There are other factors that can change the pigmentation of hair, making it lighter or darker. Scientists have divided them by intrinsic (internal) and extrinsic (external) factors:

Intrinsic factors:

Genetic defects
Hormones
Body distribution
Age
Extrinsic factors:

Climate
Pollutants
Toxins
Chemical exposure


Hair-raising facts:

An average scalp has 100,000-150,000 hairs.


Hair is so strong that each hair can withstand the strain of 100 grams (3.5 ounces). An average head of hair could hold 10-15 tons if only the scalp was strong enough!


Human hair grows autonomously, that is each hair is on its own individual cycle. If all our hair were on the same cycle, we would molt!


Hair has the highest rate of mitosis (cell division). An average hair grows 0.3 mm a day and 1 cm per month.