One thing that parrots, humans, and elephants have in common is that they are all vocal learners, meaning they can change the composition of the sounds they make, by changing pitch or the order of a song, for example. The list of species that YouTubers claim can dance is much longer, including ferrets, dogs, horses, pigeons, cats, fish, lizards, snakes, owls, camels, chimpanzees, turtles, ducks, hamsters, penguins, and bears, but they don't pass scientific muster. As domestic species like dogs and horses don't appear have any dancing aptitude, it suggests that this talent doesn't develop entirely from exposure to music. Its origin lies deeper, within the biology of the species.
Human culture has transformed dancing into a form of art, a means of expression. But beneath that scaffolding lies something far more ancient.
Darwin himself noted the apparent similarities between dance rituals in birds and humans in The Descent of Man and Selection in Relation to Sex, writing, "the males sometimes pay their court by dancing, or by fantastic antics performed either on the ground or in the air." He continues, "With birds of paradise a dozen or more full-plumaged males congregate in a tree to hold a dancing-party, as it is called by the natives: and here they fly about, raise their wings, elevate their exquisite plumes, and make them vibrate, and the whole tree seems, as Mr. [Alfred] Wallace remarks, to be filled with waving plumes…One observer, who kept several pairs alive, did not doubt that the display of the male was intended to please the female."
If Darwin was right, and dancing is used as a means for selecting mates – then dancing ability might correlate with the genetic quality of the dancer. In other words, dancing ability might serve as a signal that communicates one's own desirability as a mate. In 2005, William Brown and colleagues from Rutgers University and the University of Washington published a paper in Nature demonstrating that this might indeed be the case.
The researchers used motion capture technology to record people dancing to the same song. They also calculated, for each dancer, the degree to which their bodies were symmetrical. Previous research has indicated that this feature, called fluctuating asymmetry, is related to a person's attractiveness, whether based on odour, voice, or facial appearance. (Note, however, that the use of this measurement is controversial.)
The researchers showed animations, derived from the motion capture process, to 155 people and asked them to rate the dance abilities of the cartoon dancers. They found that males who were more symmetrical were thought of as better dancers than males who were more asymmetrical. (Video samples of symmetrical and asymmetrical dancers can be found here.) Symmetry explained nearly half of the total variation in dance ability for the men.
Symmetrical females were also rated as better dancers than their asymmetrical counterparts, but this only explained less than one quarter of the variation in their dance skills. What this means is that dance ability was a more useful indicator of one's quality as a prospective mate for men than for women, a pattern that would be expected in species where females are thought to be the more selective sex. At least three other research groups have found evidence to support the notion that differences in dance ability among human males reflects some underlying biological or genetic quality, and that females are attentive to those differences.
Both dancing and courtship are, of course, made more complicated and more elaborate thanks to human culture. Strip away that culture, though, and the distinctions among species melt away. When it comes to the birds and the bees, humans might be more like the birds than they realise.