What’s with body hair?

Pondering the evolution and science of body hair reveals some intriguing insights about hairy men…and women!

Body hair in abundance

Look closely enough and we actually are  as hairy as an ape.

To the naked eye, the human body appears virtually hairless compared to other primates, but closer inspection tells a different story. Our bodies are covered with about 5 million hair follicles. That’s roughly the same density of hair as a chimpanzee, it’s just that the hairs are not as coarse.

“Hair is the second fastest growing tissue in the human body, after bone marrow.”

Anthropologists tell us that humans once had a protective coating of hair covering their entire bodies which helped to regulate body temperature and protect skin from the sun. According to evolutionary biologist Darren Curnoe of the University of New South Wales, scientists believe our body hair grew shorter as we evolved from walking on all fours, to standing, keeping our bodies cool while running in pursuit of food.

So, what is the purpose of hair on your body?

Body hair plays a part in regulating body temperature. Ever wondered what goosebumps are? These occur when tiny muscles around the hair follicle cause the hairs to stand up and trap more heat near the body, in response to cold. This works well for animals with thick fur or body hair, not so well for us humans anymore, now that our bodies are covered in a fine layer of fuzz.

The hair on our head insulates the only part of our body where layers of fat are absent, providing protection from the sun while preserving body heat. Studies have shown that even facial hair (moustaches and beards) awards some protection from ultra-violet radiation.

Other research findings imply that beards may play a part in complex facial communication, signalling status and aggressiveness. Female participants tended to perceive bearded faces as older and ascribe higher social status to them than they did when the same men had clean shaven faces. Images of men displaying aggressive facial expressions were also rated as more aggressive when beards were present.

The hairier the better?

Nasal hair plays a less ambiguous role in our wellbeing. There are two types of nose hair which work together to protect us. The ones you might feel tempted to trim are called vibrissae. These act like a strainer, preventing harmful particles from entering the body where they can cause an infection which may pass to the brain. Deep in our noses are microscopic cilia which are responsible for moving mucus away from your lungs, to the back of the throat where it can be coughed out.

All body hair is connected to touch receptors in the skin which some researchers believe make it vital to our tactile perception. A recent study compared the ability of participants with and without arm hair, to detect ectoparasites, or bed bugs. Results showed that those with body hair were more likely to pick up on the presence of bugs.

And there’s some suggestion that mosquitoes may find it tougher to reach your skin to bite you if you’re especially hairy.

What’s the story with beards and baldness?

Men grow beards because hair follicles respond aggressively to testosterone, which men tend to have in abundance. Hormones called androgens, which are present in both sexes, stimulate body hair (known as vellus hair) to darken and coarsen. Men have higher levels of androgens than women, so their body hair tends to be more prolific.

While it’s hormones that stimulate facial hair growth, genetics determine how thick and dark a man’s facial hair will be, so a fine goatee may be seen as something of an ancestral asset.

The most common form of hair loss for men is known as male pattern baldness, brought about by a combination of genetic factors and hormonal changes with age. A male hormone called dihydrotestosterone which gives males such characteristics as a deep voice and muscle mass, is shown to cause old hairs on the scalp to be replaced by progressively shorter and thinner hairs, beginning at the temples and crown of the head.

Apparently the ‘bald and beard’ look is in, so if you can’t grow much hair on your head, you could let it rip with a full fashion statement on your face instead.

Does hair grow back thicker after shaving?

This is a myth. Hormonal changes are largely responsible for any changes in the thickness or pigment of your hair. Also, the rate at which your hair grows is largely determined by genetics, nutrition, and nerve function. You can’t make it grow faster, or thicker.

Everyone’s hair grows at different rates, but on average this would be around 1.25cm a month for the hair on your head, in your ears and up your nose. The finer hair on your body tends to reach a certain length then stop growing and eventually fall out.

Hair for good or bad

Some correlation has been drawn between the prevalence of beards and political uncertainty, according to Professor Rob Brooks from The University of New South Wales who says "When the economy tanks, beards go up".

The bottom line is, though we may be more preoccupied with how to do away with it than what it’s doing for us, body hair serves some important functions for our anatomy.

Sources:

Human fine body hair enhances ectoparasite detection | Biology Letters (royalsocietypublishing.org)

Body hair - The not-so-naked ape | Science & technology | The Economist

Ask evolution: Why do men have beards? | SBS Science

Why Do Men Have Facial Hair but Women Don't? | Live Science

ACD A-Z of Skin - Androgenetic Alopecia (in men) (dermcoll.edu.au)

https://www.betterhealth.vic.gov.au/health/ConditionsAndTreatments/hair

Dosimetric investigation of the solar erythemal UV radiation protection provided by beards and moustaches - PubMed (nih.gov)

Beards augment perceptions of men's age, social status, and aggressiveness, but not attractiveness | Behavioral Ecology | Oxford Academic (oup.com)

How Did We Get Here? - Why are we so hairy? - YouTube

https://www.ncbi.nlm.nih.gov/books/NBK544232/

https://www.sciencelearn.org.nz/resources/177-the-body-s-first-line-of-defence

https://www.dermcoll.edu.au/atoz/androgenetic-alopecia-men/ 

Monday's medical myth: shaved hair grows back faster and thicker (theconversation.com)

All information contained in this article is intended for general information purposes only. The information provided should not be relied upon as medical advice and does not supersede or replace a consultation with a suitably qualified health care professional.