A specific gene has been identified that determines whether people have wet or dry earwax. The difference in cerumen type has been tracked to a single base change (a single nucleotide polymorphism) in a gene known as "ATP-binding cassette C11 gene", specifically rs17822931. Dry-type individuals are homozygous for adenine whereas wet-type requires at least one guanine. Wet-type earwax is associated with armpit odor, which is increased by sweat production. Researchers have conjectured that the reduction in sweat or body odor was beneficial to the ancestors of East Asians and Native Americans who are thought to have lived in cold climates.