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Hair helps keep you warm, right? But hair can also keep you cooler than bare skin, as long as the hair is not too thick. So says a study in the journal PLoS ONE. [Conor L. Myhrvold, Howard A. Stone and Elie Bou-Zeid, What Is the Use of Elephant Hair?]
Researchers studied elephants, which have very thin coats of hair. It's easy for the beasts to overheat: they may face temperatures of up to 120 degrees Fahrenheit, and they don't have much skin surface area to radiate the heat relative to their big body volume.
That's where the hair comes in. The researchers wrote equations modeling the elephants' hairy skin. As they expected, thick hair traps air and keeps the body warm. But below a certain density, hair stops insulating and wicks heat off the body instead—helping the elephants get rid of an extra 20 percent of their body heat, especially on windless days.
Heat sinks inside computers work in a similar way, with pins sticking up to help dissipate the interior heat.
The researchers speculate that hair may have actually evolved to help animals stay cool, because it first sprouted in mammals over a hundred million years ago in a hot climate. Hair-raising times, indeed.
—Christopher Intagliata
[The above text is a transcript of this podcast.]
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6 Comments
Add CommentAh. And dinosaurs evolved feathers from scales for the same reason?
Reply | Report Abuse | Link to thisWill someone please help me understand the "hair stops insulating and wicks heat off the body instead"... especially on windless days? And does this hypothesis support our being "naked apes", given that we are neither naked nor apes? Is it fair to say that I'm as hairy as an elephant?
Reply | Report Abuse | Link to thisI think what they are saying is that hair can act the same way as cooling fins, like you see on an air cooled motorcycle engine, or an old radial recip airplane engine, or the thin aluminum fins on your computer's CPU cooler. These "cooling fins" greatly increase the surface area and therefore the increase the amount of heat that can be transferred to the air.
Reply | Report Abuse | Link to this@way2ec We are apes, at least in the same family. We certainly don't belong in any other group. And compared to them, we are naked. As for being as hairy as an elephant, I guess it would all have to do with the density of your hair.
Reply | Report Abuse | Link to thisHair insulates by creating millions of little closed off pockets, trapping air close to the skin. The insulation properties probably stop when the spaces between the hairs gets to be too large with a large opening to the air and then wicks up the thinner hair shafts.
Reply | Report Abuse | Link to thiswe are - most certainly - both naked AND apes.
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