Human beings are an extremely complex and highly developed species with capabilities far beyond the animals that are related closest to us. We have the capability of higher thinking and have complex problem solving abilities, and yet our species has still been developed greatly on our natural and sexual instincts. Sexual dimorphism: the difference between males and females in the same species, (Samal et al., 2007) is a great way to acknowledge these instincts. Sexual Dimorphism is evident in a large number of animal species, including humans. In humans, men are generally taller and more muscular than women, while women are generally shorter and have higher levels of adipose, or fat (Wells, 2012). Men also develop facial hair, while women develop wider hips and breasts (Dixson, 2009). Why is it that humans are so sexually dimorphic? Is there an evolutionary reason that men are more muscular than women, or that women have more prominent hips than men?.
The most commonly believed explanation for these differences is a combination of sexual selection and natural selection. Sexual selection was suggested by Darwin (1871) in his "Sexual Selection Hypothesis," which proposed that sexual dimorphism evolves when a person has an advantage in either competition for a mate, or in mate choice (Hedrick & Temeles, 1989). Competition for a mate, and mate choice, has been categorized into two separate types of sexual selection: Intra-sexual selection and inter-sexual selection respectively. Natural selection on the other hand is the process where species that are better adapted to their environment survive and reproduce offspring, passing on their advantageous traits from generation to generation (Geary, 2002). .
By looking at some of the most obvious differences between males and females, we can assess whether sexual selection, natural selection, or a combination of both has played a more important role in the sexual dimorphism of humans; Starting with the difference in size between males and females.
