Earwax is mostly gross, but it serves a few purposes: protecting our ear canals from bacteria and dryness, assisting in cleaning and lubrication, and — surprisingly — helping anthropologists determine the migratory patterns of early humans.
While most native English speakers have wet, amber-to-brown colored earwax, there's a second type — dry, gray, and flaky. Which type of earwax you have is determined genetically, with the dry type being recessive and perhaps the result of a genetic mutation somewhere along the way. For some reason, the mutation is common among East Asians. An estimated 97 to 100 percent of people of European and African descent have the wet-type earwax, while 90 percent or more of those descended from East Asians have the dry type.
The gene that controls the relative wetness of earwax is tied to sweat, generally, and the prevailing belief amongst researchers is that the recessive gene, insofar that it reduces sweat output, had advantages in the colder climates of northern China (where, along with Korea, dry earwax is most common), where the mutation seems to have begun.
But for the rest of the world population, earwax makeup is mixed. Native Americans and people from southeast Asia, for example, exhibit dry earwax in 30 to 50 percent of the population, and it appears to occur more densely in some communities thereof than others. Armed with this information, researchers can determine in part the ancestral routes of different people and how those ancestors got to where their descendants now live.
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BONUS FACT: Whales' earwax increases over time without (mostly) discharging. This makes the amount of earwax in a whale's ear proportional to its age. As many whales (for example, baleen whales such as the blue whale, the world's largest mammal) do not have teeth, earwax buildup is one of the best ways to determine how old the whale is. For toothed whales and dolphins? Their teeth grow in layers and, much like the rings of a tree's trunk, the layers are used to determine the animal's age.
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