What Type of Symmetry Do Humans Have?

Side profile of a young woman looking at her reflection
Woman looking at her reflection (Image: Jack Hollingsworth/Photodisc/Getty Images)

Your individual degree of symmetry may give off signals that others perceive unconsciously. Humans have bodily symmetry, similar to other animals and organisms in nature, which may be a factor that helps us control and interact with other people and organisms. Symmetrical traits may have developed to help us recognize each other and control our body movements. Instances of body symmetry, or lack of symmetry, may help us identify health conditions.

Body

Humans have bilateral body symmetry, which means that it can be divided into matching halves by drawing a line down the center; the left and right sides are mirror images of each other. Bilateral symmetry may help your brain recognize when your body is in different positions and make visual perception easier. Mate selection may also be a factor associated with bilateral symmetry in humans. A December 2005 article by health and environmental reporting expert, Ker Than, reports on an experiment that indicated women are more attracted to men that have more symmetrical features.

Facial

Bilateral symmetry in humans includes bilateral symmetry of the face. Like body symmetry, facial symmetry is also associated with attractiveness. The results of a May 2008 study led by Anthony C. Little, Ph.D. of the University of Stirling suggest that facial symmetry and sexually dimorphic traits are related in human faces. Sexually dimorphic traits are traits that are different in males and females of the same species. Men with more symmetrical faces tend to have more masculine facial features, and symmetrically-faced women tend to have more feminine features. The researchers speculate that facial symmetry in humans advertises mate quality, because sex hormones facilitate sexual dimorphism, and developmental stability is also associated with facial symmetry.

Shape

Symmetry in men is associated with a different shape than female symmetry. Ideal body symmetry for men is associated with a v-shape, and ideal body symmetry in women is associated with an x-shape or hourglass figure. The v-shape in men corresponds with a wide torso that tapers down to a narrow waist line. The x-shape in women corresponds with a bust and hips that are roughly the same width. The waist has a diameter that is around 10 inches less than either the bust or hips in the ideal hourglass figure.

Arm Height

Humans have arm-height symmetry, because your height is roughly equal to the distance between your left and right fingertips when you raise and extend both arms out to the side. The distance between your fingertips is known as your arm span or wingspan. A 2001 “Journal of Orthopaedic Surgery” study led by S. P. Mohanty, Ph.D. of Kasturba Medical College and Hospital, concluded that arm span is the most reliable body parameter for predicting the height of a human. The researchers suggest that lack of wingspan-height symmetry can help identify medical problems, such as disproportionate growth abnormalities, and progressive spinal deformities after corrective spine surgery.

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