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On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.

Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.

Previous Week's Question Published: 31 July, 2003 Next Week's Question
Why most males can grow facial hair
Question
Why do men grow hair on their face, while most women don't?

Question
A good question! The occurrence of male facial hair, like any physical trait or behavior, may be explained from four different, complementary perspectives or "levels of analysis." Two provide "proximate" (immediate cause) explanations, and the other two provide "ultimate" (long-term cause) explanations. Proximate explanations describe developmental programs and physiological mechanisms, whereas ultimate explanations focus on how traits affect survival and reproduction, and their probable evolutionary history.

Let's consider your question from all four perspectives. Regarding development, male facial hair sprouts at puberty (sexual maturity), coincident with emergence of a suite of "adult" characteristics, such as increases in height and deepening of the voice. Regarding mechanism, appearance of facial hair, and the other signs of maturity, are attributable to the stimulatory effects of male hormones, particularly testosterone.

Regarding evolutionary history, varying amounts of facial hair occurs in all primates (our closest relatives), and its quantity and quality differ between the sexes in many species. This implies that sexual dimorphisms in facial hair have characterized our evolutionary lineage for millions of years.

What about the functions of facial hair? Clearly it is not necessary for survival or reproduction, since it does not occur in most women and it is minimal or absent among men in many populations. Such variations seem unrelated to climate or ecology.

Most likely, facial hair functions in "sexual selection," meaning attracting mates or intimidating rivals. For example, a beard's color and texture are known to influence womens' perceptions of a man's age, social status, and general vigor. A bushy beard also may make a man appear larger, cushion his face against blows in a fight, and hide scars from previous altercations.

Men in our culture routinely shave off their facial hair. Does this imply that beards are no longer attractive or protective in societies like ours? Perhaps you'll find out!