Mate Selection and Attractiveness - Sex and Symmetry

Ever wonder why people like Tom Cruise, Brad Pitt, Jessica Alba and Linsay Lohan are attractive? It seems like many of us will agree that there is a common standard of judging beauty, although beauty is only in the eyes of the beholders. Although the standard and definition for physical attractiveness may vary across cultures, races and regions, the criteria seem similar to most of us. Big eyes, high nose, sharp chin, defined contour of the face and so on. No doubt the standard is socially influenced, some evolutionary psychologists do figure out the body figure of males and females are the key factor in mate selection, more important than facial attractiveness. After comparing and bringing together some theories like this, scientists believe that the 'key' might be hidden in the overall morphology of live beings. They started to go into deep research checking animals' mate selection behavior and found some evidence in their hypothesis.

For a male Japanese scorpionfly, finding a mate can be a real struggle. Female scorpoonflies will mate only with males that can offer a tasty meal (usually a dead insect).competition for dead insects is fierce. Typically, once a male finds an insect, he must deferred it from other males the competition for insects often erupts in bitter combat, characterized by repeated head-butting and grappling with sharp-pointed genital daspers.

In the competition to gain access to mates, not all male Japanese scorpionfilies can be equally successful. The most successful males have qualities that help them defear other males in combat and are especially attractive to females. Biologist Randy Thornhill found one quality in particular that accurately predicts the mating success of male scorpionflies: symmetry. In Thornhill's experiments and observations, the most successful males were those whose left and right wings were equal or nearly equal in length. Males with one wing longer than the other were less likely to win fights or o copulate; the greater the difference between the two wings, the lower the likelihood of success.

Thornhill's work with scorpionflies led him to wonder if the advantages of symmetry also extended to humans. Working with psychologists Steven Gangstad, he devised some fascinating studies that suggest that male symmetry does indeed play an important role in human sexual relationships. Women find symmetrical men more attractive. The preferences of human females resemble, at least in this one respect, those of female scorpionflies. One could almost say that insects and humans share a standard of beauty.