Have you been talking about me? My ears haven’t been burning, but one of them has been itchy. I wondered what was going on with my ear canal, so I decided to look into it.
Ear Ye, Ear Ye
The ear canal or auditory canal, produces ear wax, technically known as cerumen, to keep the skin moist and acidic, trap dead skin, kill microbes, and keep out dust and bugs. A lack of ear wax could increases the chance of infection, or cause itching, which seems to be my problem. My doctor told me to add some mineral oil to my ears, and that sort of helps. But enough of my problems, let’s wax, if not poetically, at least scientifically, about cerumen.
Wax In, Wax Out
Some people have too much ear wax, which can block the ear canal and affect hearing. In Japan, having someone clean your ears is considered a sign of great intimacy and trust. If you don’t have a loved one to clean your ears, please don’t go sticking things in there yourself, even if it begins with a Q, because you could make things worse. And don't do ear candling either. Get a doctor to remove earwax and you’ll both be happier. In their 1992 paper, “Cerumen: its fascination and clinical importance: a review,” Hanger and Mulley wrote, “The removal of ear wax and subsequent improvement of hearing can be one of the most satisfying clinical experiences for patient and doctor alike.”
Ear wax is a combination of dead skin cells, sebum (the same oily stuff that builds up on your hair if you don’t wash it for a few days), and various waxes the ceruminous glands produce. Ceruminous glands are a specialized sweat gland, known as apocrine glands, which produce sweat containing fats and proteins.
Two Kinds of People
Uniting people is better than dividing them, but when it comes to ear wax, the world really is divided in two kinds of people — those with wet ear wax and those with dry. The difference has been connected to a single gene ABCC11 with two alleles or forms. The difference of a single base in the DNA sequence results in a single difference in the amino acids of the protein ABCC11. A rarer form of the dry wax form involves a longer missing sequence of genetic code. The wet wax form is dominant over the dry, so people with wet ear wax may also have one allele for the dry wax. That's why two people with wet ear wax could have a kid with dry earwax.
Humans began leaving Africa about 70,000 years ago with wet ear wax and this form is still the most common in people with European and African roots. The dry wax allele arose about 50,000 years ago in Asia according to computer simulations. The spread of the dry wax form suggests that gene had some selective advantage in northern Asia, where the dry wax form is most common. Other parts of the world tend to have in-between frequencies.
The Gland Scheme
Both forms of earwax seem to be able to fight bacteria, and ear problems are not usually serious enough for ear wax to be considered an evolutionary game changer. So the evolution of the two ABCC11 alleles maybe related to their effects on other apocrine glands.
The Scent of a Person
Some arm pit sweat glands are also apocrine glands. Dry ear wax has been associated with cooler climates, so the gene may affect heat regulation. Those with wet ear wax also tend to produce sweat that skin bacteria can turn into chemicals associated with body odour. Those with dry ear wax tend to lack, or have less of, the ABCC11 protein. Body odour has been associated with sexual preferences, so perhaps it could play a part in evolution as well.
Mammary glands are also apocrine glands. Women with wet ear wax are more likely to produce colostrum, the first breast milk produced in humans and other mammals right after childbirth, and produce more of it. Colostrum is supposed to help a newborn's health. But the ABCC11 allele which results in wet earwax may also have an association with breast cancer probability.