Dance has long been recognized as a signal of courtship in many animal species, including humans. Better dancers presumably attract more mates, or a more desirable mate.
What's seemingly obvious in everyday life, however, has not always been rigorously verified by science. Now, a study by scientists at Rutgers, The State University of New Jersey, for the first time links dancing ability to established measures of mate quality in humans.
Reporting in Thursday's edition of the British science journal Nature, Rutgers anthropologists collaborating with University of Washington computer scientists describe how they created computer-animated figures that duplicated the movements of 183 Jamaican teenagers dancing to popular music. The researchers then asked peers of the dancers to evaluate the dancing ability of these animated figures. The figures were gender-neutral, faceless and the same size -- all to keep evaluators from boosting or dropping dancers' scores based on considerations other than dance moves.
The researchers also evaluated each dancer for body symmetry, an accepted indicator in most animal species -- including humans -- of how well an organism develops despite problems it encounters as it matures. Symmetry, and its association with attractiveness, therefore indicates an organism's underlying quality as a potential mate. The study showed that higher-rated dancers were typically people with greater body symmetry.
"At least since Darwin, scientists have suspected that dance so often plays a role in courtship because dance quality tracks with mate quality," said Lee Cronk, associate professor of anthropology. "But this has been hard to study because of the difficulty of isolating dance movements from variables, such as attractiveness, clothing and body features. By using motion-capture technology commonly employed in medical and sports science to isolate dance movements, we can confidently peg dancing ability to desirability."
Cronk and postdoctoral research fellow William Brown also examined results by the sex of the dancer. They found that symmetric males received better dance scores than symmetric females and that female evaluators rated symmetric men higher than male evaluators rated symmetric men.
"In species where fathers invest less than mothers in their offspring, females tend to be more selective in mate choice and males therefore invest more in courtship display," Brown said. "Our results with human subjects correlate with that expectation. More symmetrical men put on a better show, and women notice."
The researchers worked with a group of Jamaicans, building on earlier studies of physical symmetry in that population. The test group was ideal for a scientific study of dance, since in Jamaican society, dancing is important in the lives of both sexes. The dancers ranged in age from 14 through 19, and each danced to the same song, popular at the time in Jamaican youth culture. The researchers affixed infrared reflectors on 41 body locations of each dancer, from head-to-toe and arm-to-arm, to capture and measure detailed body movements. They fed data into programs that first created dancing animations of stick figures and then converted those animations into virtual human forms.
Rutgers researchers involved in the study included Cronk and Brown, along with Robert Trivers, professor of anthropology, and graduate student Amy Jacobson. Also assisting were Zoran Popovic, associate professor, and computer science and engineering graduate students Keith Grochow and Karen Liu, all from the University of Washington.
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