Molecular evidence for absence of Y-linkage of the Hairy Ears trait.

The human Hairy Ears phenotype has traditionally been regarded as the only Y-linked heritable trait. Here, we use Y-chromosomal DNA binary-marker haplotyping to show that a cohort of southern Indian Hairy-Eared males carries Y chromosomes from many haplogroups of the Y-phylogeny, which, under a hypothesis of Y linkage, would require multiple independent mutations within a single population. We further show that there is no significant difference between the Y-haplogroup spectrum in Hairy-Eared males and that in a geographically matched control sample of unaffected males. The trait cannot, therefore, be Y-linked in southern Indians, and by extension, is unlikely to be so in any population.