The single genetic switch that determines your earwax and body odor
In short: Most human traits are shaped by a complex web of many genes. However, a single nucleotide polymorphism in the ABCC11 gene acts as a definitive biological switch, dictating whether your earwax is wet or dry, and whether your sweat carries a distinct odor.
While most physical characteristics are polygenic, the ABCC11 gene provides a rare example of a visible trait controlled by a single nucleotide polymorphism (SNP). Specifically, a mutation at base position 538—where guanine (G) is replaced by adenine (A)—determines the phenotype. The GG and GA genotypes result in a dominant wet earwax type, characterized by a sticky, brown consistency and an acrid underarm odor. In contrast, the recessive AA genotype produces dry, flaky earwax and mildly odored sweat.
The mechanism lies in protein stability and glycosylation. The guanine-containing alleles produce a protein that is glycosylated, whereas the adenine allele does not. This lack of glycosylation means the resulting protein is only partially degraded by proteasomes, leaving functional transporters on the cell surface. This quantitative difference in protein dosage on the cell membrane is likely a key factor in the presence of osmidrosis, or underarm odor associated with apocrine secretion.
Evolutionary biologists use this genetic marker to trace ancient human migrations. The allele A appears to have originated in Northeast Asia and spread globally, following a geographical gradient. Today, the frequency of this allele shows a north-south and east-west downward trend, being highest among Korean and Chinese populations. While some researchers have investigated whether the wet earwax phenotype correlates with breast cancer susceptibility, this remains a subject of ongoing scientific debate.
Beyond earwax, the ABCC11 transporter is a member of the ATP-binding cassette superfamily, specifically the MRP subfamily. It functions as a membrane pump involved in transporting molecules like bile acids, conjugated steroids, and cyclic nucleotides. Some theories suggest that the evolution of odorless sweat in ancient Northern Eurasian populations may have provided an adaptive advantage in cold climates.
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Sources
- Summary by Intellect · source: A SNP in the ABCC11 gene is the determinant of human earwax type - Nature Genetics
- Also: ABCC11
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