Sexual Dimorphism
Sexual Dimorphism
Katie True
Abstract:
Human subjects were observed to find if sexual dimorphism exists in the form of height, shoulder width, and head circumference. Fifty-one male and sixty-five female subjects were used in the experiment, each with a unique height, shoulder width, and head circumference. The average shoulder width difference from males to females was five centimeters. The average difference with height between females and males was thirteen centimeters, and in head circumference the average difference was two centimeters. The males were larger in all the cases. Sexual dimorphism was found to exist strongly in height, males being taller, and slightly in head circumference and shoulder width. Males were only being slightly larger in those areas.
Introduction:
Sexual dimorphism is the presence of physical differences, besides sex organs, between the sexes (1). These physical differences can be anything from colors and size, to the presence of certain traits. Although sexual dimorphisms are species (and possibly regional) specific, a few general trends exist among most species. One of these trends is explained using Rensch’s rule, which states that size dimorphism increases as body size increases, with males being the larger sex, but the size dimorphism will decrease when females are the larger sex (2). Although this trend has been recognized, the reasons behind it are still unknown. In our experiment, we examined if sexual dimorphism exists in humans in the form of height, head circumference, and shoulder width. With the strong presence of sexual dimorphisms in other species, we hypothesized that some form exists in humans as well. The prediction has been that females would be smaller, as in many other species, and as a result, their head circumference, shoulder width, and height would be smaller than males. It was assumed that there will be a correlation between height, head circumference, and shoulder width, as one increases, the other
Katie True
Abstract:
Human subjects were observed to find if sexual dimorphism exists in the form of height, shoulder width, and head circumference. Fifty-one male and sixty-five female subjects were used in the experiment, each with a unique height, shoulder width, and head circumference. The average shoulder width difference from males to females was five centimeters. The average difference with height between females and males was thirteen centimeters, and in head circumference the average difference was two centimeters. The males were larger in all the cases. Sexual dimorphism was found to exist strongly in height, males being taller, and slightly in head circumference and shoulder width. Males were only being slightly larger in those areas.
Introduction:
Sexual dimorphism is the presence of physical differences, besides sex organs, between the sexes (1). These physical differences can be anything from colors and size, to the presence of certain traits. Although sexual dimorphisms are species (and possibly regional) specific, a few general trends exist among most species. One of these trends is explained using Rensch’s rule, which states that size dimorphism increases as body size increases, with males being the larger sex, but the size dimorphism will decrease when females are the larger sex (2). Although this trend has been recognized, the reasons behind it are still unknown. In our experiment, we examined if sexual dimorphism exists in humans in the form of height, head circumference, and shoulder width. With the strong presence of sexual dimorphisms in other species, we hypothesized that some form exists in humans as well. The prediction has been that females would be smaller, as in many other species, and as a result, their head circumference, shoulder width, and height would be smaller than males. It was assumed that there will be a correlation between height, head circumference, and shoulder width, as one increases, the other
References: 1. Futuyma, Douglas J. 2005. Evolution. Mahwah: Sinauer Associates, 2005. 2. Dale, James. 2007. “Sexual Selection Explains Rensch’s Rule of Allometry for Sexual Dimorphism.” Biological Sciences 274, vol. 1628 3. “Principles of Biology I Lab Manual”, Spring 2010, Department of Biology, Georgia College and State University 4. Pawlowski, Boguslaw, and Grazyna Jasienska. 2005. “Women’s preferences for sexual dimorphism in height depend on menstrual cycle phase and expected duration of relationship.” Biological Psychology 70, col. 1: 38-43. 5. Willmore, Katherine E., Charles C. Roseman, Jeffrey Rogers, Joan T. Richtsmeier, and James M. Cheverud. 2009. “Genetic Variation in Baboon Craniofacial Sexual Dimorphism.” Evolution 63, vol. 3: 799-806.