Wednesday, 9 March 2016

In Defence of Earwax

For something that is located so close to our brains, we spend surprisingly little time thinking about our earwax. That is likely because earwax doesn’t appear to do a great deal for us. Mostly, it is just a nuisance that we have to clean out every once in a while.

That may be the common perception, but earwax is far more useful and interesting than we think. For starters, the type of earwax you produce is directly linked to your genetic ancestry and has implications for your personal hygiene. Yes, as it turns out, there are actually two distinct types of earwax. If your ancestors hail from Africa or Europe and you stick a Q-tip in your ear (something that is never actually advisable as you’re more likely to pierce an eardrum than to get anything clean) you are likely to pull out something yellow and wet. Undertake the same ill-advised ear regimen if you happen to come from a family with links to Northern Asia and your earwax is far more likely to be white, dry, and flakey.


It may seem like a trivial biological quirk, but evolution is a picky business and triviality is rarely tolerated. If it served no functional difference, we would expect the proportions of people with each type of wax to be basically random, but they’re not. Among Europeans and Africans, 97 to 100% have wet earwax and 80 to 95% of North Asians have dry earwax. The numbers are a little more mixed for South Asian, Native American, and Pacific Island Demographics (30 to 50%), but there is definitely some selection going on.

So what is the functional difference? Well, as unpleasant as it may be to hear, wet earwax is sticky and it stinks. The stickiness is thought to help keep insects from crawling into your ear canal if you are unfortunate enough to live somewhere where that is likely. As for the stink, we’re not sure, but it may have something to do with pheromones. Wet, smelly earwax is caused by the same genetic mutation that produces the chemical in sweat that bacteria feed uponto produce body odour, so those of us who are now self-conscious about the smell of our ears might need to stock up on deodorant as well.


Earwax isn’t only interesting because of the stench implications, however. It can also be used as a marker of physical health. Scientists can take a sample of your earwax and determine whether or not you are suffering from certain diseases, long before they could discern the same thing from your blood or urine. Ironically enough, the two diseases earwax is best equipped to diagnose in their early stages are ones named for their eventual effects on urine: Maple Syrup Urine Disease and Alkoptunuria (black urine disease). The former may sound hilarious, and is in fact named for the sweet smell it gives to urine, but that smell comes from enzymes a person’s body would normally use to provide nourishment. Peeing out things you need to live is generally bad news and Maple Syrup Urine Disease can be fatal.


Finally, earwax can be useful in determining details about personal life history. This isn’t something we use it for in humans just yet, but in 2007, when a blue whale died in a collision with a ship near Santa Barbara, California, marine biologists were able to use a plug of its earwax (which happened to be over 25 centimeters – or nearly 10 inches long) to determine the levels of stress hormones in its body and the contaminants in the water it swam through at various points in its life. Whale earwax is laid down in alternating light and dark layers, each representing about six months of time. Human earwax generally doesn’t get to this point, but it may still be useful in determining exposure to toxic chemicals and other harmful agents in forensics.



Try to keep all this in mind next time you carelessly stick a finger in your ear to scoop out some wax. The gunk on your finger holds secrets about your family, medical, and personal history. So, in a very real sense, you are what you pull out of your ears.


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