"Two distinct genetically determined types of earwax are distinguished -- the wet-type which is dominant, and the dry type which is recessive. Asians and Native Americans are more likely to have the dry type of cerumen (grey and flaky), whereas Caucasians and Africans are more likely to have the wet type (honey-brown to dark-brown and moist) [3]. Cerumen type has been used by anthropologists to track human migratory patterns, such as those of the Inuit [4].

The difference in cerumen type has been tracked to a single base change (an SNP) in a gene known as "ATP-binding cassette C11 gene". In addition to affecting cerumen type, this mutation also reduces sweat production. The researchers conjecture that the reduction in sweat was beneficial to the ancestors of East Asians and Native Americans who are thought to have lived in cold climates"
http://en.wikipedia.org/wiki/Earwax
http://blog.tenderbutton.com/?p=187