A total of 49 genes have been found to influence earlobe shape and attachment, new research has found.
Earlobe shape is often used as a simple example for how a single gene can determine a physical feature. But even the shape of the humble earlobe is influenced by scores of genes, according to the study, published in the American Journal of Human Genetics.
Scientists at the University of Pittsburgh assessed the earlobe shape of 10,000 study participants, from whom they also collected genetic data. Six genes were linked to earlobe shape, substantially complicating the traditional picture of how genes influence lobe shape.
Looking at an even broader pool of participants, many more genes were found to play a role in earlobe shape. The Pittsburgh researchers used data from the US-based personal genetics company 23andMe. Comparing 65,000 people's earlobe shape and genetic data confirmed the link with those six genes. It also found another 43 genes involved.
'Sometimes the genetics of a fairly simple trait are actually quite complex,' said lead author Dr John Shaffer.
As well as shedding light on the complex genetics of a facial feature, the research could have clinical implications further down the line.
'By understanding that complexity, we can work toward treatments for genetic conditions, several of which have distinct facial features that involve the earlobe, including Mowat-Wilson Syndrome, which can cause cupped ears with protruding lobes,' Dr Shaffer said.
The study has also contributed to a debate in genetics on how best to identify genes linked to traits such as facial features. Smaller studies with fewer participants – such as the first analysis of 10,000 people – can study fewer genes but in more depth, and potentially find more robust associations. But larger studies can cast the net wider and potentially lead to a more comprehensive picture of which genes influence a particular trait.
As the larger study successfully picked out the six genes that were found in the smaller one, it suggests the latter approach can be very accurate as well as wide-ranging. The next step is to find out the functions of those genes.
'We've got these 49 genes that we know affect earlobe attachment, but we don't know how they work together or interact with one another,' said geneticist and biostatistician Professor Eleanor Feingold, a co-author of the study. 'Figuring that out is the next step.'