A recent study on chins revealed that there is no universally preferred chin type. The study, published in the Public Library of Science on April 3 by Zaneta Thayer '08 and anthropology professor Seth Dobson, showed that indigenous Australian populations had the most distinctive chin shape pattern.
The study throws into question a facet of the universal facial attractiveness hypothesis, which asserts that certain facial features are universally preferred because they are reliable signs of mate quality. These features, such as a broad chin on men, will become consistent in shape across populations due to natural selection, according to the hypothesis.
The study disproved the hypothesis by demonstrating that there is significant variation in chin shape across populations, Thayer said. This variation suggests that chin shape is independent of sexual selection and that facial preferences differ between geographic populations. Thayer and Dobson, who chose to study the subject because humans are the only primates with chins, are the first to evaluate the universal facial attractiveness theory by examining the patterns of variation in the shape of the traits instead of using data collected on facial preferences.
The majority of the remains used in the study were dated from the 1800s, before globalization and mass media proliferated Western ideals of beauty around the world. The bones are still recent enough, however, to reflect modern chins, Dobson said.
In order to compare chin shape, Thayer traced the contours in the jaw and quantified the chin curvature using mathematical analysis.
Thayer began preparing for this study as a sophomore at the College with the aid of Dobson and her undergraduate advisor, and incorporated the data into her senior thesis. Dobson researched the evolution of chin shape during the transition from archaic to modern humans while at graduate school at the Washington University in St. Louis.
Thayer collected data from the American Museum of Natural History for three weeks during the summer before her senior year, examining 90 male and 90 female jaws from nine geographic regions in Europe, Asia, Australia and Africa.
This study builds on Thayer and Dobson's previous research on the adaptive significance of the chin, which was published in the American Journal of Physical Anthropology in 2010. The study was not designed to refute the field of evolutionary psychology, Dobson said.
"We are most interested in a dialogue with psychologists to get a fuller understanding of facial attractiveness," he said.
Thayer said the study's conclusion on a lack of universal chin type will have implications for future studies in evolutionary psychology.
Thayer, a postdoctoral candidate in biological anthropology at Northwestern University, said she expects to complete her PhD by the end of the year and hopes to return to Dartmouth as an anthropology professor. She was recently hired as an assistant professor at the University of Colorado at Denver and is currently writing her dissertation on how social inequalities can create imbalances in health, focusing on the effects of maternal stress on babies during pregnancy and conducting research in Auckland, New Zealand.
Dobson is currently researching the social functions of facial expressions in monkeys.
The results of this study, titled "Geographic Variation in Chin Shape Challenges the Universal Facial Attractiveness Hypothesis," drew attention from national media outlets including The Wall Street Journal's Ideas Market blog, NPR and the Los Angeles Times.
