Lead author Zaneta Thayer, a doctoral student at Northwestern University, and Seth Dobson of Dartmouth College said one of the theories behind universal facial attractiveness is that some facial features are universally preferred because they are reliable signals of mate quality.
But that doesn't seem to be the case with the chin, and the research challenges the assumption that the chin, commonly discussed in universal facial attractiveness literature, is consistent in shape across human populations, the researchers said.
The current study builds on previous research Thayer and Dobson conducted in 2010. They evaluated competing theories for the adaptive significance of the human chin. Thayer stressed humans are the only primates with a chin, one of the unique characteristics that defines our species.
"We found that the indigenous Australian population had the most unique chin shape pattern relative to other populations," Thayer said in a statement. "That said, even after removing this population from the analysis, significant differences remained between other populations."
The study, published in the journal PLoS One, found significant geographic differences in the chin shapes challenging Darwin's theory -- at least with regard to chin shape -- that sexual selection results in the proliferation of physical characteristics that provide a competitive advantage in the struggle to find mates.