Do you have dry, flaky earwax or the gooey, stinky type? The answer is partly in your heritage.
A new study reveals that the gene responsible for the drier type originated in an ancient northeastern Asian population.
Today, 80 to 95 percent of East Asians have dry earwax, whereas the wet variety is abundant in people of African and European ancestry (97 to 100 percent).
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Populations in Southern Asia, the Pacific Islands, Central Asia, Asia Minor, and Native North Americans and Inuit of Asian ancestry, fall in the middle with dry wax frequencies ranging from 30 to 50 percent.
Researchers identified a gene that alters the shape of a channel that controls the flow of molecules that directly affect earwax type. They found that many East Asians have a mutation in this gene that prevents cerumen, the molecule that makes earwax wet, from entering the mix.
Scientists believe that the mutation reached high frequencies in Northeast Eurasia and, following a population increase, expanded over the rest of the continent. Today distribution of the gene is highest in North China and Korea.
Wet earwax is believed to have uses in insect trapping, self-cleaning, and prevention of dryness in the external auditory canal of the ear. It also produces an odor and causes sweating, which may play a role as a pheromone.
The usefulness of dry earwax, however, is not well understood. Researchers believe it may have originated to prevent less odor and sweating, a possible adaptation to the cold climate that the population is believed to have lived in.
The research is detailed in the Jan. 29 online edition of the journal Nature Genetics.