That jutting jaw line may not be as universally attractive
as scientists have assumed.
One of the theories behind universal facial attractiveness
(UFA) is that some facial features are universally preferred because they are
reliable signals of mate quality. But a new Northwestern University study tests
one of the assumptions that the chin, commonly discussed in UFA literature, is
consistent in shape across human populations.
Researchers found significant differences in chin shape
"This suggests that either sexual selection hasn't been
important in shaping chin shape in humans or that facial preferences differ
between populations," said Zaneta Thayer, a doctoral student in
anthropology at Northwestern University and lead author of the study.
The findings also suggest that human mate choices are based
on more than just attractiveness.
"We hope that our study will encourage evolutionary
psychologists to consider how their research on facial attractiveness actually
influences 'evolutionary success' as measured through number of offspring
produced," Thayer said.
"By evaluating patterns of variation in actual trait
distribution within and between populations, we can get a better sense of what
previous selection has actually looked like in these populations."
Thayer's current study builds on previous research she and
her co-author Seth Dobson of Dartmouth College conducted in 2010. They
evaluated competing theories for the adaptive significance of the human chin.
She stressed that 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. "That said, even after removing this population from the analysis,
significant differences remained between other populations."
Thayer said researchers should think more critically about
whether facial preferences inform us about actual mate success in humans.
"Since humans have evolved to be such socially complex
individuals, it is not surprising that their mate decisions are based on more
than just attractiveness," she said.
The study, "Geographic Variation in Chin Shape
Challenges the Universal Facial Attractiveness Hypothesis," is the first
study to examine the universal facial attractiveness theory not using data
looking at facial preferences but instead using actual patterns of variation in
the shape of traits themselves. Dobson is also co-author of this study. The
article appeared in PLOS One.