The NYT reports that Japanese scientists have identified the gene that determines which kind of earwax a person has. Didn't know there were different kinds of earwax? Me either. Read and learn:
Earwax comes in two types, wet and dry. The wet form predominates in Africa and Europe, where 97 percent or more of people have it, and the dry form among East Asians. The populations of South and Central Asia are roughly half and half. By comparing the DNA of Japanese with each type, the researchers were able to identify the gene that controls which type a person has, they report in today's issue of Nature Genetics. They then found that the switch of a single DNA unit in the gene determines whether a person has wet or dry earwax. The gene's role seems to be to export substances out of the cells that secrete earwax. The single DNA change deactivates the gene and, without its contribution, a person has dry earwax.
But earwax seems to have the very humble role of being no more than biological flypaper, preventing dust and insects from entering the ear. Since it seems unlikely that having wet or dry earwax could have made much difference to an individual's fitness, the earwax gene may have some other, more important function. Dr. Yoshiura and his colleagues suggest that the gene would have been favored because of its role in sweating.
They write that earwax type and armpit odor are correlated, since populations with dry earwax, such as those of East Asia, tend to sweat less and have little or no body odor, while the wet earwax populations of Africa and Europe sweat more and so may have more body odor. Several Asian features, like small nostrils, are conjectured to be adaptations to the cold. Less sweating, the Japanese authors suggest, may be another adaptation to the cold in which the ancestors of East Asian peoples are thought to have lived.
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