Phenotypic Variation Effect on Selection

Phenotypic Variation Effect on Selection

In a recent experiment, researchers set out to determine if beards are a form of negative frequency-dependent sexual selection. Beard styles appear to gain and lose popularity throughout time. The more common this sort of trait is, the less valuable it becomes. It is mentioned in the article that beards will become popular until the trend hits “peak beard.” One interesting fact they mention is that there has been a recent boom in fuller beards after the 2008 financial crisis. There was a familiar boom in the 1920’s right after the Stock Market Crash. Since beards represent masculinity and dominance, a time where jobs are scarce is a logical time for beards to regain popularity. Researchers claimed this beard boom came about because males needed to attract females in a more competitive fashion. Therefore, this experiment is to find out if there is an advantage for having the rare trait.

There are a variety of reasons that one may prefer the rare traits. Some species, for example may want to avoid mates that are similar to previous mates. Also, some may prefer mates with novel traits. This study is not asking participants to rate whether beards are attractive or not, it is asking whether participants will deem the rare trait more attractive. Researches set up an experiment predicting that when a beard type is rare, the attractiveness will increase and the more common beard type will decrease. The experiment consisted of photos of the face and neck of 36 men with varying beard lengths. The participants were given numerous sets of pictures. One set consisted mainly of clean-shaven men, with the rarity being a beard, another set was mostly bearded men, with the rarity being clean-shaven, and the last was split even. According to the results, beards, light and heavy stubble were more attractive than clean shaven faces. When clean shaven faces were rare, clean-shaven received a higher rating of attractiveness. For the even treatment, heavy stubble was more attractive than light stubble. These results proved the hypothesis correct. Attractiveness ratings varied in a negative correlation to their frequency. This is an example of additive variance genetics. The trait does fairly well in the beginning, steadily grows and then fixates. Fixation for this trait would coincide with the “peak beard” time.

In a study performed using Poecilia Reticulata, (guppys) researchers wanted to find out if familiarities to previous mates or competitors impacted mating decisions. They wanted to know what contributed to the preferences previously selected for by the guppies for unfamiliar mates. Researchers hypothesized that if the guppies were unfamiliar with a prospective partners, they would be more likely to mate with that individual rather than a familiar individual. This theory is similar to the case discussed previously regarding the advantages