Sometimes scientific studies seem more frivolous than serious work. That does not happen too often, of course since scientific research is expensive. However there was one study published in 2005 that did seem “cute rather than deep” (in the words of psychologist Steven Pinker of Harvard University.) Actually the study was intended to demonstrate serious evolutionary implications. As such it was chosen as the cover story for the December 22/29 December 2005 issue of Nature. Thus the caption on the cover featured the expression: “Fascinating Rhythm: Dancing’s Role in Sexual Selection.” However on November 27/13 Nature withdrew this article from its published collection.
It now transpires that the study may have been fraudulent. Robert Trivers was the lead scientist in the study and William Brown was a postdoctoral researcher working under Dr. Trivers’ direction. In 2005 they published the results of a study on Jamaican teenagers. The conclusion of the study was that male Jamaican teenagers with more symmetrical bodies turned out to be better dancers. Most people would say “who cares?” But the basis of the study has deep roots in evolutionary theory. Nevertheless the lead researcher, Dr. Trivers began to suspect in 2007 that Dr. Brown had fabricated significant parts of the data set. Dr. Trivers tried to withdraw the paper, but without lead author Brown’s permission, nothing happened. Trivers continued to pursue the issue and has even self-published a booklet on the controversy. (see Nature May 9, 2013 pp. 170-171)
So what is the issue? Who cares how well Jamaican teenagers dance and why was this chosen as the most important article in the December 22/29 (2005) issue of Nature (a publication that is extremely selective as to what articles they accept.) Apparently it all goes back to Charles Darwin. This man was very concerned that natural selection, his proposed mechanism to drive evolution, could not account for natural beauty in living creatures. There are, for example, amazing birds in the highlands of New Guinea. Some of these birds exhibit most amazing ornamentation. The male birds sport fancy head decorations, or tail extensions or other amazing decorations. It is hard to believe that these birds really are living. Many contemporaries of Darwin believed that such beautiful creatures as these birds-of-paradise clearly demonstrated artistry and the design choices of God. Darwin was determined to banish any such conclusions. He once famously declared that the tail of the peacock made him feel sick, since this was another amazing demonstration of beauty among living creatures.
Thus in 1871 in his book The Descent of Man, Darwin proposed the idea of sexual selection. There he declared that while ornamental characteristics or aesthetic accessories may offer little or no survival value, they nevertheless enhance the bearer’s chances of winning a mate. In this context, Darwin was particularly interested in the results of “female choice.” In this case the mating success of the males is determined by mating preferences of the females. Thus Darwin declared that beauty in animals came from the ability of females to make aesthetic choices. Of course this was all assumption on Darwin’s part, an effort to explain away a significant problem for evolution theory. Over the years, evolutionary scientists have added many more assumptions to this idea of sexual selection, and the dancing teenagers exemplify the difficulties and uncertainties of the topic.
Apparently in the 1990s, some studies showed that several invertebrates and some animals with backbones tend to seek mates with symmetrical features. Scientists then began to wonder if physical symmetry can be connected to sexual selection. Moreover, there was another issue involved too. They also wondered if bodily symmetry could be connected to better health. Thus Trivers began to measure the bodies of Jamaican teenagers. He then looked to see if individuals with more symmetrical bodies were also better runners. This led to comparisons to see if those with more symmetrical bodies were also better dancers. The interest in dance came also from Darwin who speculated that dancing is a courtship ritual which displays genetic fitness.
The question therefore arises as to why biologists would think that a more symmetrical body displays genetic fitness. In order for evolution theory to work, the individuals producing more offspring also need to exhibit better health than those leaving fewer offspring. However beauty does not necessarily go with fitness. At least in theory, the biologists had to connect the two issues. Thus an article by William Brown in Proceedings of the National Academy of Sciences (2008/08/15) declared: “Body size and shape seem to have been sexually selected in a variety of species, including humans, but little is known about what attractive bodies signal about underlying genotypic [genetics] or phenotypic [health] quality.” In order to deal with that question scientists made a choice. “A widely used indicator of phenotypic quality in evolutionary analyses is degree of symmetry.” But why should bodily symmetry be so significant?
Biologists speculate that bodies which are more equal on both the left and right sides, are not only more “attractive” to peers, but they also indicate that they possess better genetic controls. An article on the issue in Biological Review (2002 vol. 77 pp. 27-38) discussed the “widely held — but poorly substantiated — belief” that bodily symmetry is a good indicator of level of fitness. The idea is that every individual starts off life as a fertilized cell with one set of genetic instructions. When there are marked differences between right and left sides of the body, scientists suggest that this reflects an inability of the developing individual to strongly control the developmental process (such as rates of cell division on each side of the body). Scientists then assume that these variations in development are good predictors of poorer health and fitness later in life. There is however some controversy over this issue. Nevertheless some scientists use bodily symmetry as a good measure of health in individuals and populations.
With this background in mind, we can look more closely at the Jamaican teenagers. The scientists assumed that dance is a sexually selected courtship signal. If dance is to function as such from an evolutionary point of view, it should also reveal the genetic and health qualities of the dancer. The criterion scientists choose to assess in this context is bodily symmetry. The scientists therefore measured elbows, wrists, ankles, feet, third digit, fourth digit, fifth digit and ears. It was their expectation that symmetry would be reflected in good dancing, and good dancing would reveal strong developmental stability (genetics) in the dancer’s background.
With fancy video cameras, the scientists recorded the dancing of various teenagers in such a way that neither appearance nor gender was apparent. According to the data, female observers overwhelmingly favoured the more symmetrical dancers. The article ends with another question: “Does dance ability correlate with reproductive success?” That is really the question which concerns them. Unfortunately nobody knows the answer. The hope was that long term studies would investigate whether the good dancers produced more offspring. Of course it now appears that perhaps the “best” dancers were not the most symmetrical individuals after all, if the data were indeed fabricated.
The whole issue is really quite amusing. Only in the light of evolutionary theory would one care about subjective estimates of who were the best dancers, and who had the most symmetrical elbows and fingers!! Humans have been marrying for thousands of years, yet how many ever thought to look for symmetrical body parts in one’s choice of mate? There is so much more to one’s choice of a life partner than attractive appearance in any case.
Nevertheless the issue of sexual selection is extremely important to biologists who need an explanation for beauty in birds, in butterflies and even in funnel-web spiders. Thus sexual selection as a scientific theory exhibits widespread acceptance among biologists despite very poor experimental support. The desire to explain natural phenomena like beauty in a way that excludes the work of God, has certainly led to some strange studies and dubious conclusions. Indeed the situation would be amusing if the issue were not so serious.
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