Earwax comes in two types, wet and dry. The wet form predominates in Africa and Europe and the dry form predominates among East Asians. Populations of Southern and Central Asia are roughly half and half, the New York Times reported.
The study, reported in the Monday issue of Nature Genetics, found that the switch of a single DNA unit in the gene determines whether a person has wet or dry earwax.
The researchers, led by Koh-ichiro Yoshiura of Nagasaki University, studied the gene in 33 ethnic groups around the world. The wet form was likely to have been the ancestral form before modern humans left Africa 50,000 years ago.
The dry form was detected almost universally in tests of northern Han Chinese and Koreans and is quite common in Native Americans.
The researchers also found that earwax type and armpit odor are correlated. Populations with dry earwax tend to sweat less and have little or no body odor.